Preparation and evaluation of ritodrine buccal tablets for rational therapeutic use.

Ritodrine hydrochloride (RD-HCl) tablets containing alginate (AL) and lactose (LC) with or without microcrystalline cellulose (MC) as excipients were produced as a buccal dosage form. The RD-HCl (2 mg) tablets with AL/LC but no MC swelled and dissolved gradually in the in vitro dissolution test. The tablet showing the fastest dissolution and highest drug release rate, called Tablet A1, was selected as a tablet to show rapid and prolonged absorption. However, in the in vivo buccal absorption test using rats, it could not give a plasma concentration over the human minimal effective level (15 ng/mL). The modified tablet containing AL, LC, MC and RD-HCl (4 mg), named Tablet B/MC, showed better hardness and faster drug release. Tablet B/MC gave a plasma concentration over the human effective level within 15 min, and the plasma concentration was maintained at >15 ng/mL over 4 h. Moreover, the deconvolution analyses demonstrated that a prolonged high absorption rate could be achieved in vivo best with Tablet B/MC. Tablet B/MC improved the pharmacokinetic profile in comparison with Tablet A1 and the solution dosage form. The RD-HCl buccal tablets with AL, LC and MC as excipients are suggested to be possibly useful for the treatment of premature labor.