Formulation, Development and Evaluation of Timolol Maleate Sustained Release Matrix Tablets

The present work is aimed at preparing and evaluating sustained-release (SR) matrix tablets of timolol maleate (TM) using different polymers. To study the effect of nature (hydrophilic and hydrophobic) of the polymer and drug: polymer ratio (1:0.5, 1:1and 1:1.5) on the rate of drug release. Objective: Timolol maleate is a non-selective beta-adrenergic receptor blocker used in the treatment of essential hypertension, glaucoma, migraine, and for prophylaxis after myocardial infraction. It is rapidly and nearly completely (about 90%) absorbed from the gastrointestinal tract (GIT) following oral ingestion, showing 60% bioavailability. Detectable plasma levels occur within one-half hour and peak plasma levels occur in about 1-2 hours. A plasma half-life is 4 hours. In the treatment of hypertension the usual initial dosage is 10 mg twice a day, whether used alone or added to diuretic therapy. Dosage may be increased or decreased depending on heart rate and blood pressure response. The usual total maintenance dosage is 20-40 mg per day. Increases in dosage to a maximum of 60 mg per day divided into two doses may be necessary (Thomson, 2006). Although conventional tablets of Timolol maleate available in the market commercially, no study has been done so far for preparing the Timolol maleate sustained-release tablets. To improve the oral bioavailability and to reduce the dose dependent toxicity there is a need for the development of sustained-release formulations. Many patent technologies also indicated that Timolol maleate is suitable for the sustained-release (Gregory et al., 2004; Mandana et al., 2000). In-vivo drug release, biopharmaceutical evaluation, and in-vitro/in-vivo correlations were beyond the scope of this study and will be considered in future work