As of March 2010, it is still available in the United Kingdom under the brand name Palladone SR, Nepal under the brand name Opidol, and in most other European countries. Pharmacokinetics
The chemical modification of the morphine molecule to hydromorphone results in higher lipid solubility and greater ability to cross the blood–brain barrier to produce more rapid and complete central nervous system penetration. On a per milligram basis, hydromorphone is considered to be five times as potent as morphine; although the conversion ratio may vary from 4–8 times, five times is in typical clinical usage. The development of tolerance also may vary among individuals. Patients with renal abnormalities must exercise caution when dosing hydromorphone. In those with renal impairment, the half-life of hydromorphone may increase to as much as 40 hours. The typical half-life of intravenous hydromorphone is 2.3 hours. Peak plasma levels usually occur between 30 and 60 minutes after oral dosing.The onset of action for hydromorphone administered intravenously is less than 5 minutes and within 30 minutes of oral administration (immediate release). Metabolism
While other opioids in its class, such as codeine or oxycodone, are metabolized via CYP450 enzymes, hydromorphone is not. Hydromorphone is extensively metabolized in the liver to hydromorphone-3-glucoronide, which has no analgesic effects. As similarly seen with the morphine metabolite, morphine-3-glucoronide, a build-up in levels of hydromorphone-3-glucoronide may produce excitatory neurotoxic effects such as restlessness, myoclonus and hyperalgesia. Patients with compromised kidney function and older patients are at higher risk for metabolite accumulation.
The hydrochloride salt is soluble in three parts of water, whereas a gram of morphine hydrochloride dissolves in 16 ml of water; for all common purposes, the pure powder for hospital use can be used to produce solutions of virtually arbitrary concentration. When the powder appeared on the street, this very small volume of powder needed for a dose means that overdoses are likely for those who mistake it for heroin or other powdered narcotics, especially those that have been diluted prior to consumption. Endogenous production
Hydromorphone is made from morphine via catalytic hydrogenation and also is produced in trace amounts by human and other mammalian metabolisms of morphine. It occasionally appears in assays of opium latex in very small quantities, apparently forming in the plant in an unknown percentage of cases under poorly understood conditions. Bacteria
Some bacteria have been shown to be able to turn morphine into closely related drugs, including hydromorphone and dihydromorphine among others. The bacterium Pseudomonas putida serotype M10 produces a naturally-occurring NADH-dependent morphinone reductase that can work on unsaturated 7,8 bonds, with result that, when these bacteria are living in an aqueous solution containing morphine, significant amounts of hydromorphone form, as it is an intermediary metabolite in this process; the same goes for codeine being turned into hydrocodone.The process gave rise to various concentrations of hydromorphone, dihydromorphine, hydromorphinol, and oxymorphone during the experiments.