Pethidine is a fully synthetic opioid. It is used for severe to very severe pain, such as that that may occur after accidents or surgery.
What is pethidine?
Pethidine is a fully synthetic opioid. It is used for severe to very severe pain. When given intravenously, maximum effect is achieved in about 3 to 10 minutes. Pethidine is the oldest fully synthetic opioid. It was first synthesized in 1937. In Germany, it is gradually being replaced by younger preparations, but worldwide it is still considered one of the most important strong analgesics. The structure of pethidine is a simplified replica of the atropine molecule. It is produced in a two-step synthesis. In drugs, pethidine is a white crystalline powder that is readily soluble in water. It is considered an anesthetic, and as such is only available on medical prescription and is subject to correspondingly strict controls. In commerce, pethidine can be found thereby as an injection solution or in the form of tablets; suppositories are also available.
Pharmacological action
Since pethidine belongs to the group of opioid analgesics, its action is exerted at the so-called opioid receptors in the brain. The active ingredient mimics the body’s own neurotransmitters. By binding to the receptors, these inhibit the transmission of pain sensation and pain perception. Pethidine ensures that even very severe pain is perceived by the patient as less extreme than it actually is. Accordingly, pethidine has a similar effect to morphine, but is five times weaker and consequently has a weaker mood-elevating effect. Pethidine exhibits analgesic, antitussive, spasmolytic, respiratory depressant, and sedative effects. It contributes to a decrease in blood pressure and an increase in heart rate. Administration is possible orally, rectally, intramuscularly, and intravenously.
Medical use and application
Pethidine is used in the treatment of moderate to very severe acute and also persistent pain as soon as non-opioid analgesics or even weak opioids show no effect. It is used, among other things, for pain caused by tumors, for pain caused by a myocardial infarction, or as part of postoperative analgesia. It is also effective for postoperative tremor. Furthermore, pethidine is used in the treatment of colic and also pancreatitis (acute or chronic inflammation of the pancreas). Since pethidine forms the active metabolite norphetidine, it is not suitable for permanent therapy because norphetidine can cause seizures. The duration of action of pethidine is approximately 2 to 4 hours. When administered intravenously, the maximum effect is reached after about 3 to 10 minutes; when administered intramuscularly, the effect peaks after about 20 to 40 minutes. Pethidine is contraindicated in cases of hypersensitivity reactions to the active ingredient, respiratory insufficiency, acute bronchial asthma, certain cardiac arrhythmias, increased intracranial pressure, convulsive states, diabetic acidosis, alcoholism and drug addiction, severe liver disease, and Addison’s disease (primary adrenocortical insufficiency), among others. It is also not advisable in cases of low blood pressure, impaired kidney function, thyroid dysfunction (hyper- or hypothyroidism), and diseases of the urethra. In the first three months of pregnancy, pethidine should also not be taken, but during childbirth it is quite applicable as a painkiller in its lowest possible dose. Pethidine is not suitable for use in children and adolescents and 16 years of age.
Risks and side effects
Side effects that commonly occur with pethidine administration include a drop in blood pressure, respiratory dysfunction, palpitations or a slowing of the heartbeat, increase in intracranial pressure, dizziness, lightheadedness, change in mood, perceptual disturbances, delusions, and agitation. If pethidine is injected into the vein very quickly, bronchial spasms, nausea and vomiting, hiccups, and constriction of the pupils may also occur. If pethidine is used over a long period of time, constipation or disturbances in bladder emptying may result.Furthermore, spasms in the bile ducts, impaired kidney function or allergic hypersensitivity reactions may occur. If pethidine is injected into the vein, the formation of red wheals and pain along the respective blood vessel are possible. When pethidine is taken concomitantly with antiepileptic or analgesic drugs, adverse interactions may also occur, such as attenuation or potentiation of the effects of pethidine or the other drug.
