Extended-releaseformulations of morphine are those whose effect last substantially longer than bare morphine, availing for e.g. one administration per day. Conversion between extended-release and immediate-release morphine is easier than conversion to or from an equianalgesic dose of another opioid with different half-life, with less risk of altered pharmacodynamics.
Brand names for this formulation of morphine include Avinza, Kadian, MS Contin, MST Continus, Morphagesic, Zomorph, Filnarine, MXL and Dolcontin. MS Contin is a trademark of Purdue Pharma, and is available in the United States, and Australia. In the UK, MS Contin is marketed by NAPP Pharmaceuticals as MST Continus. MS Contin is a DEA Schedule II substance in the United States, a Schedule 8 drug in Australia and a Schedule 2 CD in the UK. Avinza is made by King Pharmaceuticals and Kadian is made by Actavis Pharmaceuticals. Unlike the MS Contin brand and its generic versions, Kadian and Avinza are designed to be 12- to 24-hour release, not 8- to 12-hour. So instead of 2-3 times a day dosing, it can be 1-2 times. MST Continus and MXL are registered copyright and trademark of Napp Pharmaceuticals and are available in the UK. MXL is a 24-hour release formula designed to be taken once daily. It is available in doses between 30 mg and 200 mg in 30 mg intervals. MST Continus is a 12-hour release formula, therefore it is given 2 times per day. It is available in the following doses: 5 mg, 10 mg, 15 mg, 30 mg, 60 mg, 100 mg and 200 mg tablets.
Dosage comparison
For constant pain, the relieving effect of extended-release morphine given once or twice every 24 hours is roughly the same as multiple administrations of immediate release morphine. Morphine sulfate pentahydrade has a higher molecular mass than morphine base, and therefore 10 mg morphine sulfate pentahydrate contains approximatively 7.5 mg of morphine free base. Extended-release morphine can be administered together with "rescue doses" of immediate-release morphine pro re nata in case of breakthrough pain, each generally consisting of 5% to 15% of the 24-hour extended-release dosage.
Structure
Pellet formulations can be used for controlled release of the drug in the body whereas powder filled pellets generally cannot. The plastic spheres containing powder have micropores that open at varying PH levels, to maintain a mostly constant release during transit through the digestive tract. The spheres themselves, the outer shells, pass undigested in most patients. Another use these style medications have is that they can be given via NG tube, the pellets being very small. This makes them one of the only extended release oral medications that can be given by feeding tube.
