The present work aimed to characterize transdermal drug delivery systems of pinacidil monohydrate in vivo by monitoring the effect of the TDDS on blood pressure of methyl prednisolone acetate induced hypertensive rats. The blood pressure of rats was measured using a noninvasive rat BP instrument based on cuff tail technique. A significant fall in rat BP (P<.01) was observed in treatment of hypertensive rats with all the formulations, which was maintained for 48 hours. Interformulation comparison revealed that formulation B-4 was the most effective with 37.96% reduction in BP (160.33±4.96 vs 99.44±4.46 mmHg). It was concluded that a single patch application of pinacidil TDDS (B-4) can effectively control hypertension in rats for 2 days. The system holds promise for clinical studies.