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Physicochemical Stability of Extemporaneously Prepared Oral Suspension of Fluconazole 50 mg/mL in SuspendIt™

  • Kendice Ip is currently a pharmaceutical research chemist specialized in analytical method development, validation and transfer. She earned her bachelor’s degree in chemistry at University of Houston and is expected to complete a master’s degree in regulatory science at University of Maryland, Baltimore in 2018. She also attends short-term courses to expand her knowledge in analytical method development. Kendice is experienced in the chemical analysis of pharmaceutical raw materials and compounded preparations, and polymer process materials. In 2015, she joined the analytical team in research and development department of PCCA, where she has been since that time. While at PCCA, Kendice has focused on analytical method developments and stability studies of compounded preparations, and has authored several scientific publications.

     EMAIL logo     ,

    Ashley Shan is a research chemist in Professional Compounding Centers of America (PCCA). She obtained her master degree in analytical chemistry in Texas A&M University. Her domain of interest are stability study of compounded formulas to support the formulation development in PCCA.

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    Maria Carvalho is a Portugal and UK-certified pharmacist with a PhD in extemporaneously prepared medications by the University College of London (UCL). During her 13 years of experience, Maria practiced in community pharmacy, hospital pharmacy and the pharmaceutical industry, in Europe and the USA. She was a teaching assistant at the UCL School of Pharmacy (UK) and an invited teacher at the University Fernando Pessoa (Portugal).

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    Stacey Baker, BS, CPhT, has been a compounding technician since 2000. She has been responsible for the training and education of other technicians and pharmacy interns over the course of her pharmacy career. She joined the PCCA Formulation Development team in 2012. Her work focuses on new formula development, and updating and testing existing formulations. She has extensive experience with equipment, compounding technique and calculations making her a valuable resource in the compounding industry. She earned her Bachelor of Science in Biology and Chemistry from Texas A&M University – Kingsville in 2011. She continues to attend educational events to broaden her knowledge base, where she is also part of the events and education team. She sits on the board of directors for the Fort Bend Women’s Center STARS volunteer auxiliary.

         and

    Daniel Banov, RPh, MS, Director of PCCA’s Research & Development team, earned his pharmacy degree from the College of Pharmaceutical Science of the University of Mogi das Cruzes in Brazil, and earned his Master in Science from the College of Pharmaceutical Science of the University of São Paulo, Brazil.

    Before joining PCCA, Daniel was the Director of Fórmula Médica Compounding Pharmacy in São Paulo, and was a university teacher and a cosmetic developer and consultant for physicians, spas and aestheticians. He was also the founder of the Anti-aging Society in Brazil. Daniel currently has eleven granted U.S. patents and several others pending.
Published/Copyright: April 19, 2018
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Pharmaceutical Technology in Hospital Pharmacy
From the journal Pharmaceutical Technology in Hospital Pharmacy Volume 3 Issue 2

Abstract

Background

There is a lack of an age-appropriate formulation of fluconazole. The extemporaneous preparation of an oral suspension with an extended beyond-use-date may represent a good therapeutic alternative for the paediatric population.

Methods

A fluconazole 50 mg/mL oral suspension was prepared and evenly distributed into twenty amber plastic bottles: ten bottles were stored in controlled room temperature (25 °C) whereas the remainder ten bottles were stored in refrigerated temperature (5 °C). The physical characteristics (colour/appearance, odor, pH and density) and chemical characteristics [fluconazole concentration using Ultra High Performance Liquid Chromatography (UPLC)] of the oral suspension were tested at nine pre-determined time-points over a period of 182 days.

Results

The density, pH and mean concentration of the oral suspension did not change significantly. The recovery of fluconazole ranged from 92.67 % to 98.79 % (5 °C) and from 94.31 % to 100.02 % (25 °C), both within the specification limits.

Conclusions

A palatable, sugar-free formula was developed for fluconazole 50 mg/mL in the oral suspending vehicle SuspendIt™ to allow an easy and rapid extemporaneous preparation in the hospital setting. The beyond-use-date of the formula was determined using a valid, stability-indicating analytical method and it was concluded that the extemporaneously prepared oral suspension is stable for 6 months at refrigerated and controlled room temperature.

Keywords: stability; extemporaneous preparation; fluconazole; oral suspension; paediatrics

Introduction

Fluconazole is a synthetic triazole with antifungal activity that impairs the synthesis of fungal cell membranes by inhibiting cytochrome P450-dependent enzymes in sensitive fungi, such as: Blastomyces dermatitidis, Candida spp., Coccidioides immitis, Cryptococcus neoformans, Epidermophyton spp., Histoplasma capsulatum, Microsporum spp., and Trichophyton spp [1]. It is given by mouth in the treatment and prevention of fungal infections in children, such as the mucosal and dermal candidiasis. Dosage strengths commonly range from 3–12 mg/kg daily, depending on the therapeutic indication and the age of the patient [2]. Fluconazole has a good safety profile and is well-tolerated in the paediatric population [3]. In the United States (US), oral fluconazole is commercially available as tablets (50 mg, 100 mg, 150 mg and 200 mg); and as powder for oral suspension (10 mg/mL and 40 mg/mL) using sucrose as sweetening agent [4]. Solid dosage forms commonly represent a problem for children who cannot swallow capsules or tablets; and also for the caregivers who frequently have to cut tablets in multiple halves to adjust the dosage strength. Sucrose, though a very popular sweetening agent, has been linked with some adverse health effects such as tooth decay and obesity [5]. When the commercial medicines available do not meet the needs of individual patients, extemporaneous preparations may be regarded as an alternative treatment option. Oral suspensions may then be extemporaneously prepared to include alternative excipients and dosage strengths adapted for the paediatric population. These medicines are especially important in the hospital setting considering the particular, and often critical, health conditions of hospitalised patients who are likely to benefit the most from customized medicines [6]. Although oral suspensions may be rapidly prepared, allow dosing flexibility and are easy to administer, their formulation and stability are usually complex. Issues with solubility, uniformity, taste masking and physical, chemical and microbiological stability must be considered when preparing oral suspensions [7, 8]. Hospital pharmacists need stability studies and standard operating procedures to prepare and dispense oral suspensions with the appropriate quality and safety. There are currently hundreds of teams performing stability studies worldwide [9, 10], which can be used as bibliographic references to assign beyond-use-dates (BUDs) to extemporaneous preparations.

Yamreudeewong et al. assessed the stability of a sugar-free fluconazole (1 mg/mL) oral suspension, prepared by reconstituting the powder from triturated 100-mg tablets with deionized water, and determined a BUD of 15 days (4, 23 and 45 degrees Celsius) [11, 12]. However, fluconazole powder should have been used instead since commercial tablets may have different excipients, depending on the proprietary brand/generics used, which is likely to affect the stability of the extemporaneous preparation [7]. Furthermore, 15 days is a short BUD for children who have to take the fluconazole oral suspension for longer periods. Laporte et al., on the other hand, studied the quality of fluconazole oral suspensions (30 mg/mL and 100 mg/mL) prepared by 4 US community pharmacies and concluded that these had poor accuracy and precision, plus the physical characteristics differed among pharmacies, raising awareness for the need of standardized preparations [13].

Fluconazole is a commonly prescribed antifungal agent in paediatrics and hence the importance of developing a standardized, sugar-free oral suspension which can be extemporaneously prepared with an extended BUD. Universal vehicles have been developed for the easy and rapid preparation of oral suspensions with assured quality and stability. SuspendIt™ is a proprietary oral suspending vehicle indicated in paediatrics that includes the following ingredients: water, amorphophallus konjac root powder, monk fruit extract (natural sweetener), xanthan gum, potassium sorbate, sodium benzoate, citric acid and disodium EDTA. It has special thixotropic properties that thickens upon standing to minimize settling of particles and becomes fluid upon shaking to allow convenient administration; it is also sugar-free, paraben-free, dye-free and gluten-free, which is beneficial in paediatrics. A few stability studies have already been published on SuspendIt™: clindamycin hydrochloride 10 mg/mL, spironolactone 5 mg/mL, trimethoprim 20 mg/mL and sulfadiazine 100 mg/mL [14, 15, 16].

The purpose of this study was to determine the physicochemical stability of extemporaneously prepared oral suspension of fluconazole (powder) 50 mg/mL in SuspendIt™, for a period of six months.

Materials and methods

Extemporaneous preparation of fluconazole 50 mg/mL oral suspension

A formula was developed for an oral suspension of fluconazole 50 mg/mL in SuspendIt™ taking into account the physicochemical characteristics of fluconazole (powder) and the desired organoleptic characteristics of the oral suspension, a palatable formula adequate for the paediatric population. Fluconazole is a white or almost white crystalline powder soluble in alcohol but only slightly soluble in water [1]. The chemical structure of fluconazole is shown in Figure 1. The unpleasant taste and bitterness of fluconazole were masked using a flavouring agent and two sweeteners, in addition to the monk fruit extract included in SuspendIt™. The flavouring agent chosen was orange for its citrus properties; it is the flavour included in Diflucan®, a proprietary fluconazole powder for oral suspension [17]. The sweetening agents chosen were acesulfame potassium and steviol glycosides. Acesulfame potassium is an artificial sweetener, 100–200 times sweeter than sucrose, which is safe and commonly blended with other sweeteners [5]. Steviol glycosides, on the other hand, are natural sweeteners extracted from the leaves of the plant Stevia (Stevia rebaudiana Bertoni) and are 350–400 times sweeter than sucrose [18]. The formula developed for an oral suspension of fluconazole 50 mg/mL in SuspendIt™ is shown in Table 1.

Figure 1: Chemical structure of fluconazole: (left) stylized representation, showing atoms (except hydrogen) as colour coded circles; (right) conventional skeletal formula (adapted from molekuul_be/Shutterstock.com).
Figure 1:

Chemical structure of fluconazole: (left) stylized representation, showing atoms (except hydrogen) as colour coded circles; (right) conventional skeletal formula (adapted from molekuul_be/Shutterstock.com).

Table 1:

Formula and method of preparation for an extemporaneously prepared oral suspension of fluconazole 50 mg/mL in SuspendIt™.

FORMULA For 100 mL
Fluconazole5 g
Acesulfame Potassium0.2 g
Steviol Glycosides 95 %0.2 g
Orange Flavour2 mL
Vehicle: SuspendIt™up to 100 mL
METHOD OF PREPARATION
1. Calculate the required quantity of fluconazole and excipients for the total amount to be prepared.
2. Weight and/or measure each ingredient accurately.
3. Triturate the fluconazole and the sweetening agents using a glass mortar and pestle to reduce particle size.
4. Slowly add approximately 10 % of the vehicle to the mortar and mix thoroughly to make a smooth suspension.
5. Add the flavouring agent while mixing.
6. Slowly add approximately 30 % of the vehicle to the mortar and mix well until a homogeneous suspension is obtained.
If available, use a beaker equipped with a SpinBar or an Electronic Mortar and Pestle (EMP).
7. Transfer the suspension to a measuring cylinder and complete the required volume with the remainder vehicle.
8. Package and label.
Additional Notes
Storage: Store in an airtight container.
Labelling: Shake well before use.

A total of 1,000 mL of fluconazole 50 mg/mL oral suspension (batch number 05122015–02) were prepared at Professional Compounding Centers of America (PCCA) by the Research & Development (R&D) department. The method of preparation is detailed in Table 1. Fluconazole powder (batch number C166546), Acesulfame Potassium (batch number C167872), Steviol Glycosides 95 % (batch number C169214), Orange Flavour (batch number C169665) and SuspendIt™ (batch number 6,812,932) were all obtained from PCCA (Houston, TX). Following preparation, the oral suspension was evenly distributed into twenty 50 mL prescription amber plastic bottles (Figure 2a). Ten test bottles were stored in an environmentally controlled chamber (ThermoScientific, model number 3940) at a relative humidity of 60 %±5 % and a temperature of 25 °C±2 °C (also referred to as controlled room temperature; the temperature maintained thermostatically that encompasses the usual and customary working environment of 20°-25° (68°-77°F), as defined in the United States Pharmacopeia (USP) General Chapter:<659>Packaging and Storage Requirements [19]). The remainder 10 test bottles were stored at a temperature of 5 °C±3 °C in a laboratory refrigerator (a cold place in which the temperature is controlled between 2° and 8° (36° and 46° F), as defined in the USP General Chapter:<659>Packaging and Storage Requirements [19]; Sheldon Manufacturing, model number 2020). The temperature and humidity were daily monitored and registered.

Figure 2: Prescription amber plastic bottle (50 mL) with oral syringe (A) and measuring cylinders (50 mL) with sample oral suspensions of fluconazole 50 mg/mL withdrawn from the storage conditions (B).
Figure 2:

Prescription amber plastic bottle (50 mL) with oral syringe (A) and measuring cylinders (50 mL) with sample oral suspensions of fluconazole 50 mg/mL withdrawn from the storage conditions (B).

Physical and chemical stability of fluconazole 50 mg/ml oral suspension

For the physical and chemical stability testing of the fluconazole 50 mg/mL oral suspension, one test bottle was withdrawn from each storage condition (refrigerated temperature and controlled room temperature) at pre-determined time points, as follows: days 0, 7, 15, 30, 42, 63, 92, 119, and 182. Prior to opening, each bottle was shaken vigorously for about 30 seconds to ensure homogeneous sampling of the oral suspension. Sampling was performed by withdrawing an aliquot from the middle of the test bottles.

Physical stability testing

The physical characterization of the oral suspension consisted in visually inspecting the samples withdrawn from the storage conditions for colour/appearance and odor, and testing for pH and density. The determinations obtained on day 0 were set as the baseline for appearance, odor, pH and density. The colour/appearance and odor of the samples were determined in a 50-mL graduated cylinder (Figure 2b). The pH was measured using a Horiba LaquaTwin pH meter (Kyoto, Japan). The pH meter was calibrated at pH 4.0 and 7.0 with certified pH buffer solutions before each use. The density was measured using a Fisher Scientific Grease Pycnometer model number 03–247Q (Hampton, NH). Density measurements were performed in triplicate and the average of the readings was reported.

Chemical Stability Testing

The chemical characterization of the oral suspension consisted of a validated, stability-indicating Ultra High Performance Liquid Chromatography (UPLC) assay testing. The determinations obtained on day 0 were set as the baseline for the fluconazole concentration throughout the study. All measurements were performed using a Waters (Milford, Massachusetts) Acquity UPLC system equipped with a Waters separation module (QSM); a Waters column manager heater/cooler (CM); a Waters Acquity ultraviolet photo diode array (PDA) detector; and a Waters auto sampler (FTN). The chromatographic column used was a Waters Cortecs C18 (1.6 µM) 2.1 mm x 50 mm (part number 186,007,093; batch number 0119343391). The chromatographic data was acquired and processed using the Waters Empower 3 software.

The UPLC assay testing was designed in accordance to the ICH “Harmonised Tripartide Guideline: Stability Testing of New Drug Substances and Products Q1A(R2)” [20]. It consisted of a reverse phase, isocratic chromatographic method with two different mobile phases (A:B), in a ratio of 90:10. The mobile phase A was deionized water whereas the mobile phase B was HPLC-grade acetonitrile (VWR, Radnor, Pennsylvania). The injection volume was 2 µL and the flow rate was 0.8 mL/min with a run time of 2 minutes. The column temperature was maintained at 40 °C and the sample tray at 4 °C. The ultraviolet PDA detector was set to an acquisition wavelength of 190–400 nanometers and a detection wavelength of 215 nanometers.

The samples for UPLC were prepared by pipetting 0.5 mL of the fluconazole 50 mg/mL oral suspension to a 50-mL centrifuge tube and by diluting the suspension with 24.5 mL of deionized water. Following vortex-mixing and sonication, the resulting solution with the extracted fluconazole was centrifuged for 10 min; 1 mL of the supernatant was transferred to a 10-mL volumetric flask and diluted with 9 mL of deionized water. The diluted sample solution was then pipetted to a 2-mL microtube and centrifuged for 10 min. Finally, the supernatant was transferred to an UPLC vial for assay testing.

At each pre-determined time point, one test bottle was withdrawn from each storage condition (refrigerated temperature and controlled room temperature) and sampling was performed in triplicate for UPLC assay testing. The corresponding diluted extracts were injected in triplicate and, therefore, each value reported corresponds to an average of nine injections. Each value was quantitated by a five-point linear regression line determined from five reference standards, which were prepared on each the day of the testing.

Method Validation

The UPLC assay testing was validated taking into account the ICH “Harmonised Tripartide Guideline: Validation of Analytical Procedures: Text and Methodology Q2(R1)” [21] and the USP General Chapter: <1225>Validation of Compendial Procedures [19].

The validation parameters tested were the system suitability, linearity, accuracy, precision (repeatability and intermediate), robustness, solution stability and specificity, as described below. The acceptance criteria for the method validation parameters is displayed in Table 2.

Table 2:

Acceptance criteria and results of the method validation parameters.

Validation parametersAcceptance criteriaResults
System suitability– Relative Standard Deviation (RSD) ≤ 1.0 %RSD0.2%
Tailing factor1.37
– Tailing factor ≤ 2.0
– Column efficiency ≥ 2000Column efficiency10,935
– Resolution ≥ 2.0Resolutionn/a
Regression line806.26x – 321.11
Linearity– R2 ≥ 0.995R20.9998
– y-intercept ≤ 1.5 % of target concentrationy-intercept0.40 %
– Residuals ≤ 1.5 % of target concentrationResiduals0.41 %
AccuracyAt 80 %, 100 %, and 120 % of target concentration: – 98.0 % ≤ recovery ≤ 102.0 %Recovery at 80 %100.5 %
Recovery at 100 %100.4 %
Recovery at 120 %100.1 %
Precision (repeatability)At 80 %, 100 %, and 120 % from accuracy determination: – RSD ≤ 2.0 %RSD at 80 %0.15 %
RSD at 100 %0.13 %
RSD at 120 %0.46 %
Precision (intermediate)From six determinations of standard solution at target concentration on two different days: – RSD ≤ 5.0 %RSD from instrument 10.31 %
RSD from instrument 20.71 %
RobustnessWith variations in column temperature, organic solvent content, and flow rate: – RSD ≤ 2.0 % – Tailing factor ≤ 2.0 – Column efficiency ≥ 2000 – Resolution ≥ 2.0ConditionsVariations
Column temperature±2 °C
Organic solvent content±5 %
Flow rate±1 %
Solution stabilityFrom inter-day prepared standard solution and spiked placebo solution at target concentration: – 97.0 % ≤ recovery ≤ 103.0 % – RSD ≤ 2.0 %Stability (days) and condition4 at refrigerated temperature
RSD from standard solution0.15 %
RSD from spiked placebo solution0.08 %
Specificity– No chromatogram interference – 5–20 % degradation in at least one stressed condition – Resolution ≥ 2.0 – Purity flag: noConditionsThermal and oxidation
DegradationYes (oxidation)
InterferenceNo
Resolutionn/a
Purity flagNo

  1. n/a=not applicable.

System suitability

Ensures the chromatographic system is adequate for the assay analysis; a reference standard of fluconazole 100 μg/mL was prepared and analyzed five times.

Linearity

Verifies if the concentration-response relationship is directly proportional within the given range. A stock standard for the method validation was prepared by dissolving a precise quantity of fluconazole (batch number C163994) in deionized water (Smart2Pure System; ThermoScientific Barnstead, Waltham, Massachusetts) to obtain a solution with a known concentration of about 1 mg/mL. The reference standards were prepared by diluting the stock standard with deionized water to obtain five solutions of variable concentrations of fluconazole, as follows: 80 μg/mL, 90 μg/mL, 100 μg/mL (target concentration), 110 μg/mL and 120 μg/mL The five reference standards were injected in triplicate and a linear plot of average peak area versus concentration was obtained. A regression analysis was performed to determine the correlation coefficient (R2), y-intercept and random distribution of residuals.

Accuracy

Establishes the closeness of the test results obtained by the analytical procedure to the expected value. A placebo oral suspension was prepared in accordance to Table 1, excluding the fluconazole from the formula. Nine samples of spiked placebo at fluconazole 80 μg/mL, 90 μg/mL and 120 ug/mL were examined (three replicates at each concentration). Each sample was injected in triplicate; and each measured value was quantitated against a five-point calibration curve.

Precision (repeatability and intermediate)

Determines the closeness of agreement among a series of measurements obtained from multiple sampling of the same homogeneous sample. Potential intra-laboratory and intra-assay variations were investigated as repeatability and intermediate precision, respectively. The repeatability was determined by analyzing the data collected in the accuracy analysis. The intermediate precision was determined by preparing a set of six reference standards of fluconazole 100 ug/mL on different days and by analyzing on different UPLC instruments.

Robustness

Establishes the capacity of the analytical method to remain unaffected by minor variations in the parameters. A reference standard of fluconazole 100 ug/mL and a spiked placebo sample also at fluconazole 100 ug/mL were analyzed in UPLC with minor adjustments to the following parameters: column temperature (±2 °C), organic solvent content in mobile phase (±5 %) and flow rate (±1 %).

Solution stability

Determines the inter-day stability of the testing solutions. A reference standard of fluconazole 100 ug/mL and a spiked placebo sample also at fluconazole 100 ug/mL were prepared on four consecutive days and stored at refrigerated temperature for analysis against a freshly prepared standard on the fourth day.

Specificity

Forced degradation studies were performed on the fluconazole 50 mg/mL oral suspension and on the placebo oral suspension by exposing a sample of each to the stressed conditions below, followed by extraction of fluconazole and UPLC assay testing.

  1. Thermal degradation: the two samples were placed in the oven at 60 °C for 14 days. Extraction and analysis was performed on days 7 and 14.

  2. Oxidation degradation: the two samples were exposed to Hydrogen Peroxide 20 % (diluted from Hydrogen Peroxide 30 %; batch number 410,422; VWR, Radnor, Pennsylvania) for 45 hours at room temperature and in a dark environment.

Statistical analysis

The stability of fluconazole was assessed by calculating the percentage of the initial concentration remaining at each time interval. Stability was defined as the retention of 90 % to 110 % of the initial concentration. Data from the chemical stability and density testing was expressed as mean +/- standard deviation from at least three separated samples analyzed. Along with the mean recovery, the range with 95 % confidence interval was also determined. Both lower and upper confidence limits at each time interval should satisfy the acceptance criteria of 90 % to 110 % of the initial concentration, which was determined at day 0.

Results

The oral suspension exhibited a faint beige colour and a smooth, uniform appearance, as displayed in Figure 2b. The visual inspection revealed that the colour darkened slightly towards the end of the study for the controlled room temperature. In addition, from the time point t=42 days onwards, there was some generation of insoluble particulates for both storage conditions, though easily redispersible following vigorous shaking. The oral suspension exhibited a characteristic citrus odor and there was no odor generation throughout the 182 days of the study.

The density and pH of the oral suspension stored at both temperatures did not change significantly, as displayed in Table 3. The density ranged from 0.973 g/mL to 1.020 g/mL for the refrigerated temperature; and from 0.999 g/mL to 1.021 g/mL for the controlled room temperature (changes inferior to 0.05 g/mL). On the other hand, the pH ranged from 5.21 to 5.40 for the refrigerated temperature; and from 5.20 to 5.35 for the controlled room temperature (changes inferior to 0.2 pH units).

Table 3:

Physical characterization of the extemporaneously prepared oral suspension of fluconazole 50 mg/mL stored at refrigerated temperature and controlled room temperature for 6 months.

Elapsed time (days)Density g/mL ± standard deviation*pH
Refrigerated temperatureControlled room temperatureRefrigerated temperatureControlled room temperature
(5 °C±3 °C)(25 °C±2 °C)(5 °C±3 °C)(25 °C±2 °C)
t=01.008 ± 0.0061.017 ± 0.0095.275.28
t=70.973 ± 0.0050.999 ± 0.0215.255.35
t=150.996 ± 0.0111.001 ± 0.0025.245.23
t=300.999 ± 0.0041.009 ± 0.0075.215.20
t=421.013 ± 0.0031.008 ± 0.0075.285.25
t=631.020 ± 0.0011.021 ± 0.0065.275.20
t=921.013 ± 0.0061.015 ± 0.0025.275.22
t=1191.009 ± 0.0051.013 ± 0.0015.235.22
t=1821.008 ± 0.0021.014 ± 0.0005.405.35

  1. Results presented as an average of three measurements.

Likewise, the mean concentration of fluconazole in the oral suspension stored at both temperatures did not change significantly throughout the 182 days of the study, as displayed in Table 4 and Figure 3. The concentration ranged from 47.754±0.984 mg/mL to 50.908±0.563 mg/mL for the refrigerated temperature; and from 49.066±0.828 mg/mL to 52.034±0.860 mg/mL for the controlled room temperature (changes inferior to 3.2 mg/mL). At each pre-determined time point, the concentration of fluconazole was measured by quantifying the corresponding peak in the UPLC-PDA chromatogram for each sample tested. Figures 4a to 4c show the fluconazole chromatograms of the oral suspension for 3 samples tested, in comparison to the fluconazole reference standard (Figure 4d). The mean initial concentration (t=0) of fluconazole, obtained for both storage conditions (51.533±0.211 mg/mL and 51.025±0.206 mg/mL), was used as baseline for the calculation of the percent recovery. The recovery of fluconazole ranged from 92.67 % to 98.79 % for the refrigerated temperature; and from 94.31 % to 100.02 % for the controlled room temperature (changes inferior to 6.5 %).

Figure 3: Mean concentration of fluconazole (mg/mL± standard deviation) in the extemporaneously prepared oral suspension, stored at refrigerated temperature and controlled room temperature, over a study period of 6 months. Dashed lines represent the lower and upper limits, corresponding to 90 % and 110 % of the labeled concentration (50 mg/mL), respectively.
Figure 3:

Mean concentration of fluconazole (mg/mL± standard deviation) in the extemporaneously prepared oral suspension, stored at refrigerated temperature and controlled room temperature, over a study period of 6 months. Dashed lines represent the lower and upper limits, corresponding to 90 % and 110 % of the labeled concentration (50 mg/mL), respectively.

Figure 4: UHPLC-PDA chromatograms (absorbance units vs. time) of the extemporaneously prepared oral suspension of fluconazole 50 mg/mL in SuspendIt (A) at baseline (t=0); (B) at the end of the study (t=182 days) stored at refrigerated temperature; and (C) at the end of the study (t=182 days) stored at controlled room temperature; and the chromatogram of a fluconazole 100 μg/mL reference standard (D).
Figure 4:

UHPLC-PDA chromatograms (absorbance units vs. time) of the extemporaneously prepared oral suspension of fluconazole 50 mg/mL in SuspendIt (A) at baseline (t=0); (B) at the end of the study (t=182 days) stored at refrigerated temperature; and (C) at the end of the study (t=182 days) stored at controlled room temperature; and the chromatogram of a fluconazole 100 μg/mL reference standard (D).

Table 4:

Chemical characterization of the extemporaneously prepared oral suspension of fluconazole 50 mg/mL stored at refrigerated temperature and controlled room temperature for 6 months.

Elapsed time (days)[Fluconazole]mg/mL ± standard deviation*Percent Recovery%±standard deviation*
Refrigerated temperature(5 °C±3 °C)Controlled room temperature(25 °C±2 °C)Refrigerated temperature(5 °C±3 °C)Controlled room temperature(25 °C±2 °C)
t=051.533 ± 0.21151.025 ± 0.206100.00 ± 0.42100.00 ± 0.41
t=750.908 ± 0.56351.097 ± 0.86398.79 ± 1.0998.22 ± 1.66
t=1548.058 ± 0.14249.066 ± 0.82893.26 ± 0.2894.31 ± 1.59
t=3050.537 ± 0.09752.034 ± 0.86098.07 ± 0.19100.02 ± 1.65
t=4250.512 ± 0.18351.013 ± 0.42898.02 ± 0.3698.05 ± 0.82
t=6347.754 ± 0.98450.241 ± 1.30792.67 ± 1.9196.57 ± 2.51
t=9250.315 ± 0.98450.016 ± 0.59997.64 ± 1.9196.14 ± 1.15
t=11950.136 ± 0.20349.714 ± 1.20397.30 ± 0.3995.56 ± 2.31
t=18249.602 ± 0.16050.752 ± 0.25096.25 ± 0.3197.55 ± 0.48

  1. Results presented as an average of nine measurements.

The UPLC assay testing met the acceptance criteria for all validation parameters (Table 2); it is therefore stability-indicating for the oral suspension of fluconazole 50 mg/mL.

Finally, every 95 % confidence intervals of the measured concentrations had both upper and lower limits within 90 % to 110 % of the initial concentration (46.38 mg/mL to 56.686 mg/mL at refrigerated temperature and 45.923 mg/mL to 56.128 mg/mL at controlled room temperature), except for t=63 at refrigerated temperature which had a lower 95 % confidence interval of 45.786 mg/mL.

Discussion

Fluconazole is only slightly soluble in water, the major component of the vehicle SuspendIt™, and it is therefore expected that some insoluble particulates develop with time. However, SuspendIt™ uses a patent-pending anti-sedimentation polymer complex that reduces settling and increases redispersion [22]. For this reason, after shaking vigorously for about 30 seconds, the oral suspension becomes easily redispersed to ensure accurate dosing for administration or, in this case, to ensure accurate sampling for stability testing. The label of the extemporaneously prepared oral suspension of fluconazole 50 mg/mL must therefore state “Shake well before use”, as stated in Table 1.

The color change observed in the oral suspension stored at controlled room temperature towards the end of the study is possibly attributed to the effect of temperature on the vehicle SuspendIt™. Graves et al. [15, 16] studied the stability of several active pharmaceutical ingredients (APIs) in SuspendIt™ and also observed some darkening with age, particularly for the oral suspensions stored at 40 °C.

The physical characteristics of the oral suspension remained within the specifications throughout the study and, as a result, the extemporaneously prepared oral suspension of fluconazole 50 mg/mL in SuspendIt™ is deemed physically stable at both refrigerated temperature and controlled room temperature, in amber plastic bottles, for 182 days (6 months).

The USP preconizes a High Performance Liquid Chromatography (HPLC) assay testing for the “Fluconazole for Oral Suspension” [19] but the present study was designed according to the ICH “Harmonised Tripartide Guideline: Stability Testing of New Drug Substances and Products Q1A(R2)” [20] using the UPLC assay testing instead. Both HPLC and UPLC refer to liquid chromatography used to separate the components from mixtures. The UPLC is a specially improved version of HPLC that offers less solvent consumption, faster chromatography and better resolution properties [23]. For these reasons, the authors decided to develop a new methodology for the chemical stability of the fluconazole oral suspension instead of following the corresponding USP monograph.

According to the USP, the “Fluconazole for Oral Suspension” contains not less than (NLT) 90.0 % and not more than (NMT) 110.0 % of the labeled amount of fluconazole (C13H12F2N6O) [19]. The percent recovery for fluconazole was within the specifications for the duration of the study as the minimum and maximum percent recoveries were 92.67 % and 100.02 %, respectively. However, according to the British Pharmacopoeia, the “Fluconazole Oral Suspension” contains NLT 95 % and NMT 105 % [24]. There were only 3 measurements below 95 %, as follows: 93.26 % and 94.31 % for t=15; and 92.67 % for t=63. Since the following time points presented percent recoveries over 95 %, it is likely that the lower values were obtained due to uneven sampling or differences between the reference standards. The retention time of the major peak (fluconazole) of the sample solutions corresponded to that of the reference standards, as required by the USP [19], and there were no significant extraneous peaks observed in any of the chromatograms. As a result, the extemporaneously prepared oral suspension of fluconazole 50 mg/mL in SuspendIt™ is deemed chemically stable at both refrigerated temperature and controlled room temperature, in amber plastic bottles, for 182 days (6 months).

The formula developed for the extemporaneously prepared oral suspension of fluconazole 50 mg/mL includes the API instead of commercial tablets in order to avoid formulation and/or stability issues due to the proprietary brand/generics used. It also employs an oral suspending vehicle that is free of sugar, parabens, dyes and gluten, all excipients to avoid in the paediatric population. When compared to former stability study by Yamreudeewong et al., the formula developed has a longer BUD, showing that the vehicle SuspendIt™ was able to maintain the physical characteristics and potency of the fluconazole oral suspension for a considerably longer period i. e. 6 months instead of 15 days [11].

Conclusions

There is currently a need for an extemporaneously prepared oral suspension of fluconazole due to the lack of commercial medicines adapted to the paediatric population. A palatable, sugar-free formula was developed for fluconazole 50 mg/mL in the oral suspending vehicle SuspendIt™ to allow an easy and rapid extemporaneous preparation in the hospital setting. Standard operating procedures and stability studies are very important to hospital pharmacists in order to ensure the quality and safety of the extemporaneous preparations dispensed, in particular to paediatric patients. Therefore, a stability-indicating analytical method was used to determine the BUD of the oral suspension. The present study demonstrates that the formula developed for the oral suspension of fluconazole 50 mg/mL in SuspendIt™ is stable for 6 months at both 5 °C±3 °C and 25 °C±2 °C.

About the authors

Kendice Ip

Kendice Ip is currently a pharmaceutical research chemist specialized in analytical method development, validation and transfer. She earned her bachelor’s degree in chemistry at University of Houston and is expected to complete a master’s degree in regulatory science at University of Maryland, Baltimore in 2018. She also attends short-term courses to expand her knowledge in analytical method development. Kendice is experienced in the chemical analysis of pharmaceutical raw materials and compounded preparations, and polymer process materials. In 2015, she joined the analytical team in research and development department of PCCA, where she has been since that time. While at PCCA, Kendice has focused on analytical method developments and stability studies of compounded preparations, and has authored several scientific publications.

Ashley Shan

Ashley Shan is a research chemist in Professional Compounding Centers of America (PCCA). She obtained her master degree in analytical chemistry in Texas A&M University. Her domain of interest are stability study of compounded formulas to support the formulation development in PCCA.

Maria Carvalho

Maria Carvalho is a Portugal and UK-certified pharmacist with a PhD in extemporaneously prepared medications by the University College of London (UCL). During her 13 years of experience, Maria practiced in community pharmacy, hospital pharmacy and the pharmaceutical industry, in Europe and the USA. She was a teaching assistant at the UCL School of Pharmacy (UK) and an invited teacher at the University Fernando Pessoa (Portugal).

Stacey Baker

Stacey Baker, BS, CPhT, has been a compounding technician since 2000. She has been responsible for the training and education of other technicians and pharmacy interns over the course of her pharmacy career. She joined the PCCA Formulation Development team in 2012. Her work focuses on new formula development, and updating and testing existing formulations. She has extensive experience with equipment, compounding technique and calculations making her a valuable resource in the compounding industry. She earned her Bachelor of Science in Biology and Chemistry from Texas A&M University – Kingsville in 2011. She continues to attend educational events to broaden her knowledge base, where she is also part of the events and education team. She sits on the board of directors for the Fort Bend Women’s Center STARS volunteer auxiliary.

Daniel Banov

Daniel Banov, RPh, MS, Director of PCCA’s Research & Development team, earned his pharmacy degree from the College of Pharmaceutical Science of the University of Mogi das Cruzes in Brazil, and earned his Master in Science from the College of Pharmaceutical Science of the University of São Paulo, Brazil.

Before joining PCCA, Daniel was the Director of Fórmula Médica Compounding Pharmacy in São Paulo, and was a university teacher and a cosmetic developer and consultant for physicians, spas and aestheticians. He was also the founder of the Anti-aging Society in Brazil. Daniel currently has eleven granted U.S. patents and several others pending.

Acknowledgements

The authors would like to thank Jason Wheeler, CTS, Multimedia Production Technician at PCCA, for his support and assistance with the professional photographs.

  1. Conflicts of interest: The authors are affiliated with PCCA, the manufacturer of the proprietary vehicle SuspendIt™. The stability study was performed at the Analytical Laboratory of PCCA.

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Received: 2018-2-9
Revised: 2018-3-28
Accepted: 2018-3-30
Published Online: 2018-4-19
Published in Print: 2018-6-1

© 2018 Walter de Gruyter GmbH, Berlin/Boston

Articles in the same Issue

  1. Frontmatter
  2. graphical-abstract
  3. Editorial
  4. Paediatric Needs: Challenge and Opportunities for Hospital Pharmacists
  5. Research Articles
  6. Physicochemical Stability of 5 mg/mL Pediatric Prednisone Oral Suspension in Syrspend® SF PH4
  7. Safe use of Dexamethasone in pediatrics: design and evaluation of a novel stable oral suspension
  8. Paediatric formulation: budesonide 0.1 mg/mL viscous oral solution for eosinophilic esophagitis using cyclodextrins
  9. Physicochemical and Microbiological Stability of a New Oral Clonidine Solution for Paediatric Use
  10. Formulation of a 3-months Stability Oral Viscous Budesonide Gel and Development of an Indicating Stability HPLC Method
  11. Physicochemical Stability of Extemporaneously Prepared Oral Suspension of Fluconazole 50 mg/mL in SuspendIt™
  12. Opinion Paper
  13. Development and Preparation of Oral Suspensions for Paediatric Patients – a Challenge for Pharmacists
https://doi.org/10.1515/pthp-2018-0007
Keywords for this article
stability; extemporaneous preparation; fluconazole; oral suspension; paediatrics

Articles in the same Issue

  1. Frontmatter
  2. graphical-abstract
  3. Editorial
  4. Paediatric Needs: Challenge and Opportunities for Hospital Pharmacists
  5. Research Articles
  6. Physicochemical Stability of 5 mg/mL Pediatric Prednisone Oral Suspension in Syrspend® SF PH4
  7. Safe use of Dexamethasone in pediatrics: design and evaluation of a novel stable oral suspension
  8. Paediatric formulation: budesonide 0.1 mg/mL viscous oral solution for eosinophilic esophagitis using cyclodextrins
  9. Physicochemical and Microbiological Stability of a New Oral Clonidine Solution for Paediatric Use
  10. Formulation of a 3-months Stability Oral Viscous Budesonide Gel and Development of an Indicating Stability HPLC Method
  11. Physicochemical Stability of Extemporaneously Prepared Oral Suspension of Fluconazole 50 mg/mL in SuspendIt™
  12. Opinion Paper
  13. Development and Preparation of Oral Suspensions for Paediatric Patients – a Challenge for Pharmacists
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