A once daily, controlled release, morphine sulphate suppository (Moraxen) has been launched. Schwarz Pharma, the manufacturer of Moraxen, says that the product is the first suppository to provide 24-hour pain relief from a single dose.
Moraxen releases morphine at a constant rate from a non-dissolving, ribbed, hydrogel polymer rod. The polymer used is inert, non-biodegradable and water insoluble. The company says that the rod is firm and rigid when dehydrated. However, once inserted into the rectum, it absorbs water and swells, becoming soft and rubbery. The summary of product characteristics for Moraxen says that morphine is well absorbed from Moraxen after rectal administration, achieving peak plasma concentrations within five hours. After approximately 24 hours the suppository is expelled (either during a normal bowel movement or by the patient bearing down to induce a bowel movement) and replaced to maintain pain management (see p378).