Intranasal bioavailability of apomorphine from carboxymethylcellulose-based drug delivery systems

Carboxymethyl cellulose (CMC) powder formulation of apomorphine was prepared by lyophilization and characterized with respect to the in vitro and intranasal in vivo release of apomorphine in rabbits. This was compared to apomorphine release from degradable starch microspheres (DSM) and lactose, as well as in vivo absorption after subcutaneous injection. In vitro apomorphine release from CMC was sustained, unlike that of DSM and lactose. Changing the drug loading of CMC from 15 to 30% (w/w) influenced drug release rate, which increased with increased drug loading. In vivo absorption of apomorphine from lactose, DSM and subcutaneous injection were rapid and not sustained. Slower absorption rates of apomorphine occurred from CMC. The fastest absorption rate was obtained with lactose and the slowest with CMC of 15% (w/w) drug loading. The T(max) from the CMC dosage forms were significantly prolonged compared to the immediate release forms. Plasma drug levels were sustained with CMC. The plasma concentration was maintained within 50% of the C(max), longer (15% (w/w), 70 min; 30% (w/w), 40 min) compared to the rest (lactose, 20 min; DSM, 25 min, subcutaneous injection, 35 min). The sustained plasma level of apomorphine by CMC was achieved with relative bioavailabilities equivalent to subcutaneous injection.