Dihydrocodeine is an opioid that exerts analgesic and antitussive effects. It has an analgesic potency of 0.2 and is used primarily to treat nonproductive irritable cough.
What is dihydrocodeine?
Dihydrocodeine is a drug from the opioid group that is used both analgesically (to stop pain) and to stop irritable cough. The analgesic potency of dihydrocodeine is 0.2. Analgesic potency is a measure of the analgesic effect of a drug, usually an opioid. Morphine, with an analgesic potency of 1, is used as a reference substance. Morphine thus has an analgesic effect five times stronger than dihydrocodeine. Thus, to achieve the same analgesic effect that would be obtained with one milligram of morphine, five milligrams of dihydrocodeine would have to be administered. Underlying dihydrocodeine is a phenanthrene scaffold. Dihydrocodeine exists as a white to yellowish-white solid. The chemical molecular formula of the substance is C18H23NO3, and the molecular mass is 301.4 g/mol. Dihydrocodeine is a derivative of morphine and is produced semisynthetically. Dihydrocodeine is chemically derived from codeine by adding hydrogen to it twice. Dihydrocodeine is poorly soluble in water. In finished drugs, it is most commonly used as dihydrocodeine hydrogen tartrate. This salt of dihydrocodeine can be dissolved in water in a ratio of 1:4.5. In Germany, dihydrocodeine is considered a narcotic that can be marketed and prescribed. It is listed in Annex 3 of the Narcotics Act. If codeine is contained in a drug with a content of less than 2.5% or less than 100 mg/unit, it is subject to prescription, but a narcotic prescription is not required. The documentation requirement stipulated by the Narcotics Act is also not necessary in this case. However, if dihydrocodeine is prescribed to alcohol– or narcotic-dependent individuals, a narcotic prescription is mandatory to prevent abuse.
Pharmacologic action
Dihydrocodeine is applied orally in the form of tablets, capsules, sustained-release tablets, and drops. After oral administration, it is rapidly absorbed in the intestine. The first-pass effect is strong with dihydrocodeine, resulting in a systemic bioavailability of only twelve to 34%. The maximum plasma concentration is reached after 1.6 to 1.8 hours for dihydrocodeine. It is able to cross the blood–brain barrier and the placental barrier. Dihydrocodeine also passes into breast milk. Metabolism of dihydrocodeine occurs in the liver (hepatic). Some of the substance is excreted unchanged in the urine. Dihydrocodeine has a plasma half-life of about four hours on average. The action of dihydrocodeine is due to the binding of the substance to opioid receptors. Through this binding, it attenuates the cough center and pain perception. The antitussive effect begins about fifteen to 30 minutes after oral administration.
Medicinal use and application
Dihydrocodeine is used primarily to suppress nonproductive irritable cough. However, it is also used as an analgesic for moderately severe pain. Furthermore, it can be used for heroin substitution; however, this use is permitted only in exceptional, well-founded cases. Normally, methadone or levomethadone are used for heroin substitution. Analgesically, dihydrocodeine is used mainly for the treatment of joint pain, phantom limb pain, neuropathies, and postoperative pain. The analgesic potency of dihydrocodeine is twice that of codeine.
Risks and side effects
Adverse drug effects of dihydrocodeine include sedation, euphoria, gastrointestinal disturbances (especially constipation, nausea, and vomiting), fatigue, dizziness, sleep disturbances, allergic skin reactions such as itching and rash, headache, hypersensitivity, visual disturbances and pupillary constriction (miosis), and edema. Contraction of the ureter and inhibition of the micturition reflex may also be caused by smooth muscle contraction caused by dihydrocodeine. Dihydrocodeine should not be used if hypersensitivity to dihydrocodeine exists.Furthermore, it must not be used in the presence of coma, bronchial asthma, respiratory insufficiency, chronic cough, liver dysfunction, pancreatitis, during pregnancy and lactation. MAO inhibitors must not be used concomitantly with dihydrocodeine. In addition, medicines containing dihydrocodeine must not be given to children under four years of age. As with all opioids, there is a risk of abuse of dihydrocodeine as an intoxicant. Prolonged use can lead to the development of tolerance and dependence.
