Category: Formulation and Quality
Purpose: Chemical warfare agents such as arsenicals can affect a large population when used in a battlefield or against civilian population by terrorist. In such an unlikely event, fast and effective antidotes are desired. 4-Phenylbutyric acid is a molecular target-based antidote against arsenicals being developed in our laboratories. We found that it is effective in blocking injury caused by cutaneous exposure to these chemicals. The purpose of this study is to optimize rapid delivery of high dose of 4-Phenylbutyric acid through the use of chemical enhancers such as oleic acid, oleyl alcohol and ethanol.
Methods: An HPLC method was developed for the analysis of 4-Phenylbutyric acid (4-PBA). The analysis was carried out using a reverse phase isocratic technique. A C8 column; Agilent, Zorbax Eclipse XDB-C8, (3×150 mm, 5 µm) was used as the stationary phase and the mobile phase was composed of acetonitrile: sodium phosphate buffer (Na2HPO4) at pH 7 (10:90). The detection wavelength was set at 210 nm and the total run time was 10 min. In vitro permeation studies were carried out using vertical Franz diffusion cells. Four different formulations were studied for evaluating the effect of enhancers on the permeation profile of the drug. All the formulations had the same 4-PBA concentration of 12.5% w/v but different vehicles and vehicle enhancer combinations, such as 1) Propylene glycol (PG), 2) 2.5% w/w oleic acid in PG, 3) 1.5% w/w oleyl alcohol in PG, 4) a mixture composed of glycerol: deionized water: ethanol = 1:1:1. Porcine ear skin was used as model skin for conducting the drug permeation studies. A set of two permeation studies were done using the formulations. In the first study, the groups (n=4 to 5) were 4-PBA in PG as control, 4-PBA dissolved in 2.5% w/w solution of oleic acid in PG, 4-PBA dissolved in 1.5% w/w solution of oleyl alcohol in PG and drug dissolved in a mixture of glycerol, ethanol and water at a ratio of 1:1:1. The amount of drug in donor was 0.9 mg and the sampling time points were at 0,1,2,4,8,12,22 and 24 h. In another study, the groups studied were 4-PBA dissolved in PG as control with a donor compartment drug amount of 1.8mg, 4-PBA dissolved in 2.5% solution of oleic acid in PG with a donor compartment drug amount of 1.8mg, 4-PBA dissolved in 2.5% w/w solution of oleic acid in PG with a donor compartment drug amount of 0.9 mg and 4-PBA dissolved in a mixture of glycerol, ethanol and water at a ratio of 1:1:1 with a donor compartment drug amount of 1.8mg.The sampling time points for this study was 0,1,2,4,6 and 8 h.
Results: At the end of the first 24 h study, cumulative drug amount in receptor was analyzed and there was no significant difference observed among the groups. However, the flux values were different for each group in the first 8 hours. Drug dissolved in 2.5% oleic acid had the highest flux at 155.69 μg/cm2/h, whereas, for the control group, the flux value was 76.49 μg/cm2/h. Based on these data a second study was conducted. At the end of 8h study, for the control group, the cumulative amount of drug permeated through the skin was found to be 245.17±25.65 µg/cm2, whereas for 4-PBA dissolved in 2.5% oleic acid in PG group, the amount delivered was significantly enhanced to 1825.42±112.90 µg/cm2. The permeation profile for both groups are shown in Figure.1. For the group containing a finite dose of 0.9mg PG as vehicle in donor of Franz cells and oleic acid as chemical enhancer, the cumulative amount of drug permeated through the skin was observed to be, 993.63±34.18 µg/cm2. When compared with the group containing the same formulation but an infinite dose (1.8mg), a significant difference in the cumulative amount of drug permeated was found, at the end of 8h.(Figure 2). Another formulation using ethanol as an enhancer was also investigated in this study. A direct comparison was drawn among the control group, glycerol, ethanol and water mixed at a ratio of 1:1:1 group and drug dissolved in 2.5% w/w solution of oleic acid in PG group. Cumulative amount permeated was significantly different for both the test groups when compared with the control. The group containing oleic acid as an enhancer showed significantly higher permeation when compared with the ethanol group (Figure 3)
Conclusion: Delivery of 4-Phenylbutyric acid across skin was demonstrated and was significantly enhanced by using oleic acid as a chemical enhancer. The flux profile suggests that a large quantity of the drug can be delivered very fast across skin, which is desired to provide a fast and effective antidote to a chemical warfare attack.
Mohammad Shajid Ashraf Junaid– Atlanta, Georgia
Mohammad Shajid Ashraf Junaid– Atlanta, Georgia
Ritesh Srivastava– Birmingham, Alabama
Mohammad Athar– Birmingham, Alabama
Ajay Banga– Professor and Department Chair, Mercer University, Atlanta, Georgia
Mohammad Shajid Ashraf Junaid– Graduate Student, Mercer University, Atlanta, Georgia