Identification of Factors Affecting Preservative Efficacy and Chemical Stability of Lamivudine Oral Solution Through Statistical Experimental Design

Abstract

To identify factors affecting the chemical stability and preservative efficacy of lamivudine oral liquid formulations, an optimization study using a central composite design was performed. In this design, five factors, each at three levels, were investigated: pH (4.5, 5.5, and 73, sucrose (5%, 20%. and 50% w/v), propylene glycol (0% 2%, and 5% w/v), glycerin (4% 8%, and 12% w/v). and EDTA (0.100. 0.175, and 0.250 mg/mL). All formulations contained a constant concentration of lamivudine, parabens, and artificial strawberry and banana flavors. All formulations were evaluated for preservative effectiveness against USP and BP standards and for chemical stability at 30°C and 40°C for three months. All formulations were effective against bacteria and yeasts, but indicated reduced preservative effectiveness against the mold Aspergillus niger. Preservative effectiveness improved with increasing pH (4.5 to 7.5) and to a lesser extent with increasing EDTA concentration (0.100 to 0.250 mg/mL). Increasing glycerin concentration (4% to 12% w/v) slightly decreased preservative effectiveness. Over the concentration ranges tested, no change in preservative effectiveness was noted with concentration changes in sucrose or propylene glycol. The pH was the main factor influencing the chemical stability of the drug and preservatives in this study. Lamivudine chemical stability increased with increasing pH from 4.5 to 7.5. Methyl and propylparaben showed extensive degradation at pH 7.5.     

A Stability Study of Clindamycin Hydrochloride and Phosphate Salts in Topical Formulations

The stability of clindamycin hydrochloride and clindamycin phosphate was studied in topical liquid formulations prepared with the following solvents: solvent A (70% isopropanol, 10% propylene plycol and 20% water), solvent B (48% isopropanol, polyoxyethelene ethers, acetone, salicylic acid and allantoin), solvent C (40% alcohol, acetone, polysorbate 20, fragrance and water) and “standard” (50% isopropyl alcohol, propylene glycol and water) in glass and plastic containers at 25°, 40°, and 50°C.

It was found that, in general, better stability was obtained in glass containers than in plastic containers. At 25°C both the clindamycin hydrochloride and phosphate formulations in solvent B showed poorer stability than in the other solvents irrespective of the type of container, while formulations in solvent C showed the best stability. In addition, the effect of the pH on the stability of the formulations was determined, and it was clear that at pH values below 4 the stability of all formulations decreased.     

Development of a topical suspension containing three active ingredients

The objective of this study was to develop a topical suspension that contains sarafloxacin hydrochloride (1 mg/mL), triamcinolone acetonide (1 mg/mL), and clotrimazole (10 mg/mL), and is stable at room temperature (15-28°C) for clinical usage. Due to the difference in the physicochemical properties and chemical stability profiles of these three active ingredients, it is a challenge to develop a stable suspension formulation containing these three drugs. In this study, the stability of these drugs in different buffer solutions was determined under different accelerated isothermal conditions. The Arrhenius equation was subsequently utilized to predict the room-temperature stability of these three drugs in these buffer solutions. By knowing the room-temperature solubility of the drugs in the buffer solution, the stability of the drugs in suspension was predicted. As a result, a 0.02 M phosphate buffer (pH 7.0) containing 0.02% (w/v)polysorbate 20, 1% (w/v) NaCl, and 0.1% (w/v) EDTA was determined to be an acceptable medium. In addition, 0.35% (w/v) high-viscosity carboxymethylcellulose (HV-CMC) was first selected as the suspending agent to enhance the redispersibility of the suspension. Stability data further supported that all three drugs were stable in the suspension containing HV-CMC with less than 5% potency loss for at least 6 months at 40°C and 12 months at 25°C. However, the viscosity drop of this HV-CMC formulation at 25°C and 40°C became a product stability concern. To improve the viscosity stability of the suspension, the medium-viscosity carboxymethylcellulose (MV-CMC) was selected to replace the HV-CMC as the suspending agent. The optimal combination of MV-CMC and sodium chloride in achieving the most desirable dispersion properties for the formulation was determined through the use of a 3² factorial design. The optimal formulation containing 1% MV-CMC and 1% sodium chloride has shown improved viscosity stability during storage and has been used for clinical studies.     

Influence of Uric Acid on Photostability of Sulfathiazole Sodium Solutions

The effect of uric acid as a photoprotective agent for buffered and unbuffered solutions of sulfathiazole sodium was investigated. Uric acid solution in glycerin was found to enhance the photostability of sulfathiazole sodium solutions. The higher the concentration of uric acid used, the greater was its photoprotective action within the concentration range studied. Uric acid was also found to demonstrate its photoprotective effect in the presence of either sodium sulfite or EDTA. Sodium sulfite alone in a concentration of 0.1% produced a detrimental effect on the photostability of sulfathiazole sodium in either borate or phosphate buffer of pH 9 ± 0.2. From the standpoint of the overall chemical stability of sodium sulfathiazole, uric acid appeared to be most effective when used alone in the borate buffer. However, the incorporation of 0.1% sodium sulfite in addition to uric acid contributed to the prevention of discoloration in either the borate or the phosphate buffer.     

Development of a Transdermal Delivery Device for Melatonin In Vitro Study

The present study was undertaken to develop a transdermal delivery device for melatonin and to determine the effects of system design on the release of melatonin. Melatonin(MT) diffusion characteristics from 2 solvents through a series of ethylene vinyl acetate membranes with 4.5%, 9%, 19%, 28% vinyl acetate were characterized using vertical Franz® diffusion cells. The solvent used were 40% (v/v) propylene glycol (PG) and 40%(v/v) propylene glycol with 30%(w/v) 2-hydroxypropyl-β-cytrodextrin. The best release rate (Jss = 0.795 μg/h/cm²) was obtained from the 40% PG vehicle through the 28% vinyl acetate membrane. Melatonin diffusion through this membrane with an acrylate pressure sensitive adhesive (PSA) with and without MT loading was also studied. The data revealed an interaction between MT and the PSA in the systems with MT-loaded adhesive. A MT transdermal delivery device was constructed based on the above data. Effect of storage time (1 day, 2 days, and 3 days) on the developed device was also investigated. Steady state flux values of MT did not vary significantly with storage time (p-value = 0.14). The steady state flux was 1.88 ± 0.6 μg/hr/cm²(n = 9). However, storage time did affect the burst effect of MT. Total amount of MT released in the first hour was 137.4 ± 25.7 μg after 3 days, 61.5 ± 8.9 μg after 2 days, and 43.8 ± 20.9 μg after 1 day.     

Pre-formulation and chemical stability studies of penethamate, a benzylpenicillin ester prodrug, in aqueous vehicles

Penethamate (PNT) is a diethylaminoethyl ester prodrug of benzylpenicillin used to treat bovine mastitis via the intramuscular route. Because of its instability, PNT products must be reconstituted before administration and the reconstituted injection has a short shelf life (7 days at 2-8°C). The purpose of this paper was to investigate whether the stability of PNT can be improved in order to achieve a chemically stable ready-to-use aqueous-based PNT formulation or at least to extend the shelf life of the reconstituted suspension. A chemical stability study of PNT in aqueous-based solutions as a function of pH, buffer strength, solvent mixtures and temperature, supported by studies of its solubility in mixed solvents, allowed predictions of the shelf life of PNT solution and suspension formulations. PNT degraded in aqueous solutions by several pathways over the pH range 2.0-9.3 with a V-shaped pH-rate profile and a minimum pH of around 4.5. The stability of PNT solutions in mixed solvents was greater than in aqueous solutions. For example, in propylene glycol:citrate buffer (60:40, v/v, pH 4.5), the half-life of PNT was 4.3 days compared with 1.8 days in aqueous buffer. However, solubility of PNT in the mixed solvent was higher than that in aqueous solution and this had an adverse effect on the stability of suspensions. By judicious choosing of pH and mixed solvent, it is possible to achieve a storage life of a PNT suspension of 5.5 months at 5°C, not sufficient for a ready-to-use product but a dramatic improvement in the storage life of the reconstituted product.     

In vitro release studies of piroxicam from oil-in-water creams and hydroalcoholic gel topical formulations

The importance of piroxicam, a therapeutic anti-inflammatory drug, is well known. Because of gastrointestinal disorders, dermatological dosage forms are recommended most. In our first studies, oil-in-water (O/W) creams of piroxicam (1% concentration) were prepared using glyceryl monostearate (GMS), stearic acid, and triethanolamine as additive ingredients. In our second studies, hydroalcoholic transparent gel formulations of this drug in a 0.5% concentration were prepared using hydroxypropylcellulose (HPC) as the gelling agent. The release of piroxicam from all formulations via dialysis through a cellulose membrane into phosphate buffer pH 6.8 at 37°C was studied. The effects of additives such as propylene glycol and 2-propanol on the drug release were also investigated. The release profiles from the standpoint of diffusion-controlled processes, as well as zero-order and first-order kinetics, were evaluated, and relevant parameters, such as diffusion coefficient, permeability coefficient, and partition coefficient, were calculated. The release obeys both the diffusion mechanism and first-order kinetics. The drug release from gel formulations containing 10%, 20%, and 30% propylene glycol was decreased due to the enhancement of viscosity. However, the limpidity of these formulations was improved. Moreover, the release of drug from gel formulations containing 15% and 20% of 2-propanol was increased. These results show that a hydroalcoholic gel formulation with HPC is a more suitable preparation of piroxicam when compared with an O/W cream formulation.     

Stability of 4-DMAP in Solution

A stability-indicating reversed-phase performance liquid chromatographic method was developed for the detection of 4-(N, N-dimethylamino)phenol (4-DMAP) and its degradation products under accelerated degradation conditions. The degradation kinetics of 4-DMAP in aqueous solution over a pH range of 1.12-6.05 and its stability in solutions based on propylene glycol or polyethylene glycol 400 were investigated. The observed rate constants were shown to follow apparent first-order kinetics in all cases. The pH rate profile shows that maximum stability of 4-DMAP was observed in the pH range 2.0 to 3.0. Acid/base catalysis of 4-DMAP was not affected by systems of various ionic strengths. Incorporation of nonaqueous propylene glycol or polyethylene glycol 400 in the pH 3.05 solution of 4-DMAP showed an increase in the stability at 55°C ± 0.5°C.     

Effect of Steareth-20 on the Release of Nitrofurantoin from Propylene Glycol Monostearate Microspheres

In vitro release of nitrofurantoin (NFT) from microspheres of propylene glycol monostearate (PGM) was investigated at NFT:PGM ratios of 1:1, 1:1.5, 1:3, 1:4, 1:5, and 1:9 in distilled water at 37°C. The rate and extent of drug release declined with decreasing NFT:PGM ratio. A maximum drug release of 52.4% over 24 hr was recorded for the microspheres of formulation I (highest load). The effect of Steareth-20 (ESA) over the concentration range of 0.01% to 0.1% w/w of PGM on the size of the microspheres and on the release profile of nitrofurantoin from the microsphere formulations was examined at NFT.PGM ratios of 1:1 and 1:4. The cumulative % of NFT released over a 24-hr period was found to be maximum at ESA concentration of 0.03% and 0.05% w/w of PGM. The plots of T₅₀ versus %w/w of ESA exhibited two minima, the first at 0.03% ESA and a second, weaker than the first, at 0.05% ESA, paralleling the earlier observations. Scanning electron micrographs of the exhausted microspheres revealed a very porous matrix of PGM at the ESA concentration of 0.03%. The formulations containing 0.03% and 0.05% ESA had the smallest mean particle diameter and the minimum contact angles (water over PGM-ESA films) corresponding to the two critical micelle concentrations (CMC), at 0.025% and 0.05% w/w.     

Effects of Low-Viscosity Sodium Hyaluronate Preparation on the Pulmonary Absorption of rh-Insulin in Rats

Purpose: A low-viscosity formulation for pulmonary delivery of rh-insulin as model peptide drugs was developed using a solution of sodium hyaluronate. Method: The effects of different concentrations and pH values of low-viscosity solutions of hyaluronate on the pulmonary absorption of rh-insulin were examined after intratracheal administration in rats. The permeation of fluorescein isothiocyanate (FITC)-dextran(molecular weight 4300; FD-4) and insulin through excised rat trachea in vitro were also examined. Results: The hyaluronate (2140 kDa) solutions (0.1% and 0.2%w/v) at pH 7.0 significantly enhanced the pharmacological availability (PAB) of insulin compared to the aqueous solution of insulin at pH 7.0. The absorptionenhancing effect at a concentration of 0.1% w/v hyaluronate was greater than that at a concentration of 0.2% w/v hyaluronate. Furthermore, the greatest absorptionenhancing effect was obtained, regardless of the molecular weight of hyaluronate, when the concentration of hyaluronate was adjusted to 0.47 µM. Absorption-enhancing effects were consistent with the effect of a 0.1% w/v hyaluronate preparation at pH 4.0 and 7.0 on the permeation of FITC-dextran and insulin through excised rat trachea in vitro. Conclusion: Low-viscosity hyaluronate preparation was shown to be a useful vehicle for pulmonary delivery of peptide drugs.     

Preparation of Adrenochrome Hydrogel Patch, Gel, Ointment, and the Comparison of Their Blood Coagulating and Wound Healing Capability

The aim of this study is to make an effective blood coagulant and wound healing agent, which on its topical application on ruptured skin would help in instant coagulation of blood and ongoing healing of wound. The hydrogel has been prepared by mixing 28% w/v gelatin and 21% w/v PVA in distilled water, and heated to 40°C followed by addition of a blood coagulant at a lower temperature. Beeswax, alcohol, liquid paraffin, and adrenochrome were mixed, triturated, and heated accordingly to prepare adrenochrome ointment. Polyvinyl alcohol and glycerin were mixed and heated and the drug was added at a lower temperature, and stored at 4-5°C to form adrenochrome gel. Gelatin alone has cell adhesion property. Adrenochrome is a blood coagulant. Therefore, gelatin with adrenochrome in hydrogel has a synergistic effect in wound healing. To evaluate the efficacy of these three different formulations, incisions were made on the backs of three mice and simultaneously adrenochrome containing hydrogel patch, gel, and ointment were applied on the wound and observed at regular intervals for half an hour to examine the rate of blood coagulation and kept under observation for 2 days to study the rate of wound healing. The efficacy of all these three formulations was compared to appraise the most effective blood coagulating and wound healing agent.     

Formulation development of allopurinol suppositories and injectables

Allopurinol was formulated into injectable and suppository dosage forms. The injectable formulation was prepared by dissolving allopurinol in a cosolvent system consisting of dimethyl sulfoxide (DMSO) and propylene glycol (v/v = 50/50). The stability of allopurinol in the cosolvent system was studied under accelerated storage conditions, and results indicate first-order degradation kinetics with an activation energy of 24.3 kcal/mol. The development of suppository dosage forms was performed by formulating allopurinol with polyethylene glycol (PEG) mixtures of different molecular weights. In vitro release profiles of suppositories formulated with different polyethylene bases were obtained in the pH 7.4 buffer solution using the USP 23 paddle method at 100 rpm. Results indicate that the release rate of the suppository formulations containing PEG 1500/PEG 4000 at the ratio (w/w) of 2.5/10 to 10/2.5 appeared to be similar. However, the addition of sodium lauryl sulfate in the suppository decreased the release rate of allopurinol significantly. A future study to establish in vitro/in vivo correlation (iv/ivc) is suggested.     

Development and optimization of chemically stable lipid microspheres containing flunarizine

Aim: The purpose of this study is to develop an appropriate dispersion system containing flunarizine, and most of all, to improve the chemical stability of flunarizine. Method: In this study, a higher incubation temperature (60°C), to induce a faster chemical degradation, was adopted to optimize a better vehicle, an appropriate pH value, and an effective antioxidant system for flunarizine. Results: The chemical stability of flunarizine was improved significantly in lipid microspheres (LMs) compared with the aqueous solution. The optimal formulation of LMs for flunarizine at pH 8.0 is composed of (w/v): flunarizine 0.1%, dl-α-tocopherol 0.1%, medium-chain triglyceride 5%, long-chain triglyceride 5%, soybean lecithin 1.8%, poloxamer 188 0.4 %, Tween-80 0.2%, glycerol 2.5% and l-cysteine 0.05%, Na₂SO₃ 0.15%, and EDTA 0.01%. Conclusions: The long-term stability investigation, stored at 10 ± 2°C and 25 ± 2°C for 6 months, witnessed the better chemical stability of flunarizine in LMs. An intravenous delivery system of LMs for flunarizine focusing on a better chemical stability of flunarizine has been successfully developed and optimized.     

Photostabilization of Demeclocycline Hydrochloride with Reduced Glutathione

Photodegradation of demeclocycline hydrochloride (DCL) in buffer solutions was studied in absence and presence of some potential photostabilizers under the influence of fluorescent light. Photolysis of DCL solutions followed first-order kinetics, DCL was more stable in acidic pH. Change in ionic strength of the buffer had no effect on the photolysis of DCL. Among the potential photostabilizers tested, reduced glutathione (GTH) was found to be the most effective photoprotective agent. Increase in GTH concentration decreased the photodegradation rate, but this decrease was not significant above 20 μg/ml GTH concentration. The photodegradation of DCL both in presence or absence of GTH was lowest at pH 4.5 citrate buffer, compared to acetate or phosphate buffer. A mixture of 50% (v/v) propylene glycol or 50% (v/v) PEG 400 in phosphate buffer did not demonstrate any photostabilizing effect. Aluminum foil-covered glass vials provided greater photoprotection compared to clear glass or amber glass vials.     

Stability of HI-6 in Solution

A stability-indicating reversed-phase high performance liquid chromatographic method was developed for the detection of HI-6 and its degradation products under accelerated degradation conditions. The degradation kinetics of HI-6 in aqueous solution over a pH range of 1.14 to 5.54 and its stability in propylene glycol or polyethylene glycol 400-based solutions were investigated. The observed rate constants were shown to follow apparent firstorder kinetics in all cases. The pH-rate profile shows that maximum stability of HI-6 was observed in the pH range 2.0 to 3.0 No effect of general acid/base catalysis of HI-6 was noted in the study. The degradation rate constants of HI-6 affected by different ionic strength systems. Irradiation with 254 nm UV light at 25 ±0.5°C was found when compared with the light-protected controls. Incorporation of nonaqueous propylene glycol or polyethylene glycol 400 in the pH 3.10 HI-6 solution show an increase in its stability at 70±0.5°C.     

A Stability Study of Clindamycin Hydrochloride and Phosphate Salts in Topical Formulations

Abstract

The stability of clindamycin hydrochloride and clindamycin phosphate was studied in topical liquid formulations prepared with the following solvents: solvent A (70% isopropanol, 10% propylene plycol and 20% water), solvent B (48% isopropanol, polyoxyethelene ethers, acetone, salicylic acid and allantoin), solvent C (40% alcohol, acetone, polysorbate 20, fragrance and water) and “standard” (50% isopropyl alcohol, propylene glycol and water) in glass and plastic containers at 25°, 40°, and 50°C.

It was found that, in general, better stability was obtained in glass containers than in plastic containers. At 25°C both the clindamycin hydrochloride and phosphate formulations in solvent B showed poorer stability than in the other solvents irrespective of the type of container, while formulations in solvent C showed the best stability. In addition, the effect of the pH on the stability of the formulations was determined, and it was clear that at pH values below 4 the stability of all formulations decreased.     

Influence of Uric Acid on Photostability of Sulfathiazole Sodium Solutions

Abstract

The effect of uric acid as a photoprotective agent for buffered and unbuffered solutions of sulfathiazole sodium was investigated. Uric acid solution in glycerin was found to enhance the photostability of sulfathiazole sodium solutions. The higher the concentration of uric acid used, the greater was its photoprotective action within the concentration range studied. Uric acid was also found to demonstrate its photoprotective effect in the presence of either sodium sulfite or EDTA. Sodium sulfite alone in a concentration of 0.1% produced a detrimental effect on the photostability of sulfathiazole sodium in either borate or phosphate buffer of pH 9 ± 0.2. From the standpoint of the overall chemical stability of sodium sulfathiazole, uric acid appeared to be most effective when used alone in the borate buffer. However, the incorporation of 0.1% sodium sulfite in addition to uric acid contributed to the prevention of discoloration in either the borate or the phosphate buffer.     

Formulation and in vitro evaluation of a thermoreversible mucoadhesive nasal gel of itopride hydrochloride

Itopride hydrochloride (ITO HCl) is a prokinetic agent, used in the treatment of gastrointestinal motility disorders. The aim of the study was to develop stable mucoadhesive thermoreversible nasal gel to avoid first pass effect. ITO HCl was incorporated into the blends of thermoreversible polymers like poloxamer 407 and various mucoadhesive polymers in different concentrations to increase the contact of the formulations with nasal mucosa. The compatibility between the drug and the suggested polymers was studied by Fourier transform infrared and differential scanning calorimetry (DSC). The formulations were evaluated for clarity, pH, gelation temperature, mucoadhesive strength, gel strength, viscosity, and drug content. In addition, the in vitro drug release and the dissolution efficiency (DE)% were measured. The optimized formulations that showed the highest dissolution efficiency% (DE%) in saline phosphate buffer of pH 6.4 at 35?±?0.5?°C were chosen for stability testing at temperatures of 4?±?2 and 25?±?2?°C/60?±?5% RH. It was found that F1 and F17 that contain 18% w/v poloxamer 407 and 0.5% w/v of hydroxypropylmethyl cellulose K4M or methyl cellulose (MC), respectively, showed higher stability results as indicated by their higher t₉₀ values (days).     

Development of a Lyophilized Parenteral Pharmaceutical Formulation of the Investigational Polypeptide Marine Anticancer Agent Kahalalide F

Kahalalide F is a novel antitumor agent isolated from the marine mollusk Elysia rufescens; it has shown highly selective in vitro activity against androgen-independent prostate tumors. The purpose of this study was to develop a stable parenteral formulation of kahalalide F to be used in early clinical trials. Solubility and stability of kahalalide F were studied as a function of polysorbate 80 (0.1%-0.5% w/v) and citric acid monohydrate (5-15 mM) concentrations using an experimental design approach. Stabilities of kahalalide F lyophilized products containing crystalline (mannitol) or amorphous (sucrose) bulking agents were studied at +5°C and +30°C ±60% relative humidity (RH) in the dark. Lyophilized products were characterized by infrared (IR) spectroscopy and differential scanning calorimetry (DSC). Recovery studies after reconstitution of kahalalide F lyophilized product and further dilution in infusion fluid were carried out to select an optimal reconstitution vehicle. It was found that a combination of polysorbate 80 and citric acid monohydrate is necessary to solubilize kahalalide F. Lyophilized products were considerably less stable with increasing polysorbate 80 and citric acid monohydrate concentrations, with polysorbate 80 being the major effector. A combination of 0.1% w/v polysorbate 80 and 5 mM citric acid monohydrate was selected for further investigation. Lyophilized products containing sucrose as a bulking agent were more stable compared to the products containing mannitol. The glass transition temperature of the sucrose-based product was determined to be + 46°C. The amorphous state of the product was confirmed by IR analysis. A solution composed of Cremophor EL, ethanol, and water for injection (5%/5%/90% v/v/v CEW) kept kahalalide F in solution after reconstitution and further dilution with 0.9% w/v sodium chloride (normal saline) to 1.5 μg/m. A stable lyophilized formulation was presented containing 100 μg of kahalalide F, 100 mg sucrose, 2.1 mg citric acid monohydrate, and 2 mg polysorbate 80 to be reconstituted with a vehicle composed of 5%/5%/90% v/v/v CEW and to be diluted further using normal saline.     

Content Uniformity of a Low Dose Pharmaceutical Product

ABSTRACT

Optimum homogeneity and physical stability for a Roche compound (RO) low dose formulations (0,125 and 0.250 mg Tablets i.e. 0.07 to 0.14% w/w drug load, respectively) were achieved. Direct compression powder formulations were prepared by mixing the active drug substance with Starch 1500 (ST) to form an active pre-mix. Other ingredients were added subsequently. The final powder mix was subjected to a vibration of 4 Hz frequency using a specially designed segregation unit and content uniformity was assessed for these formulations. ST was considered superior to both lactose anhydrous and Avicel PH 102 in preparing homogeneous and physically stable mixes. Production-size batches of the product were successfully manufactured (Mean Drug content = 98 100%, RSV = 2%).