Extended-release (or slow-release) formulations 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 (or "regular") 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, Australia and the UK. MS Contin is a DEA Schedule II substance in the United States, a Schedule 8 (controlled) drug in Australia and a CD2 (Controlled Drug - Schedule 2 - You have to sign when dropping off the prescription and when picking up the medication, they cannot change or do anything once you have signed to say you have received the drug.) 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 12-24 hour release, not 8-12 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 is available in the UK. MXL is a 24-hour release formula and is a 1 a day dose. It is available in doses between 30 mg and 200 mg in 30 mg intervals (equating to between 1.25 mg/hour and 8.33 mg/hour). 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 (equating to between 0.83 mg/hour and 16.67 mg/hour).
For constant pain, the relieving effect of extended-release morphine given once (for Kadian) or twice (for MS Contin) every 24 hours is roughly the same as multiple administrations of immediate release (or "regular") morphine. 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.
Pellet (spheroid) formulations (made by extrusion and spheronization) 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.
Opioid replacement therapy
According to a Cochrane review in 2013, extended-release morphine as a opioid replacement therapy for people with heroin addiction or dependence confers a possible reduction of opioid use and with fewer depressive symptoms but overall more adverse effects when compared to other forms of long-acting opioids. Retention in treatment was not found to be significantly different.
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