Preparation, characterization and in-vitro evaluation of theophylline loaded microemulsion formulations

Abstract

Theophylline is widely used as a bronchodilator drug in asthma and chronic obstructive lung disease because it is effective and inexpensive. Theophylline blood concentrations should be monitored since its therapeutic index is narrow, its optimum blood levels range from 10 to 20 μg/mL; its serious side effects take place over 20 μg/mL; its efficacy falls below 10 μg/mL blood concentrations. The aim of the present study is to formulate and characterize oil-in-water microemulsion systems for oral delivery of theophylline. Microemulsion formulations represent an interesting delivery vehicle for poorly water-soluble drugs, allowing for improving their solubility and dissolution properties. A simple and reliable UV-Spectrophotometric method was developed and validated for the determination of theophylline in the concentration range of 25- 150 μg/mL. In vitro drug release profile showed that after 1 hour, 40% of the drug released through the formulation in Simulated Intestinal Fluid at pH 6.8 as a release medium and the microemulsion formulations released more than 75% of the drug during the 5 hours study period. The globule size of drug-loaded formulations was in the range of 203.6 ± 0.2 nm. Results confirmed that the proposed microemulsion formulation containing theophylline could improve and control the drug release profile in comparison to the conventional dosage form.