Diamorphine

Diamorphine is a powerful narcotic analgesic obtained from opium which acts mainly on the central nervous system and smooth muscle. It is predominantly a central nervous system depressant but it has stimulant actions resulting in nausea, vomiting and miosis. It can provoke the release of endogenous histamine and thereby induce catecholamine release.

Diamorphine also has a powerful cough suppressant effect.

Oral administration

Oral administration of diamorphine results in measurable blood concentrations of morphine but not diamorphine or 6-acetylmorphine. The amount of circulating morphine provided by an oral dose of diamorphine was only 79% of that available from an equal amount of morphine.

h3. IM / IV / SC administration

Diamorphine is a potent opiate analgesic which has a more rapid onset of activity than morphine as the first metabolite, monoacetylmorphine, more readily crosses the blood brain barrier. In man, diamorphine has a half-life of two to three minutes. Its first metabolite, monoacetylmorphine, is more slowly hydrolysed in the blood to be concentrated mainly in skeletal muscle, kidney, lung, liver and spleen. Monoacetylmorphine is metabolised to morphine. Morphine forms conjugates with glucuronic acid. The majority of the drug is excreted via the kidney as glucuronides and to a much lesser extent as morphine. About 7-10% is eliminated via the biliary system into the faeces.

Diamorphine does not bind to protein. However, morphine is about 35% bound to human plasma proteins, mainly to albumin. The analgesic effect lasts approximately three to four hours.

Preclinical information has not been included because the safety profile of diamorphine hydrochloride has been established after many years of clinical use.