Nanocomplex System of Bupivacaine with Dextran Sulfate for Parenteral Prolonged Delivery

Abstract

An electrostatic complex system of bupivacaine (BUP), an amide‐type analgesic agent, with an oppositely charged polymer was designed for parenteral sustained delivery. The complex was prepared by admixing the drug (0.25–1.0% w/v) with different anionic polymers (dextran sulfate, carboxymethylcellulose, or carboxymethyl dextran, 1.0–5.0% w/v), and then adding calcium ion (0–1.0% w/v) as the noncovalent crosslinking agent. Negatively charged complexes ranging from 10 to 2000 nm were formed after the positively charged BUP molecules amalgamated with the polymers after gentle agitation. Drug released from the complex was markedly sustained either by increasing the polymer to drug ratio, or by increasing the calcium ion content. The optimized nanocomplex consisted of the drug, dextran sulfate, and calcium ion at the ratio of 1:20:20 w/w/w, which supplied a sustained release profile over 7 days. Therefore, novel nanocomplex is expected to be an effective tool to provide a sustained release of the analgesic agent.