Relief of moderate to severe pain not responsive to non-opioid analgesics. Pre-operative medication. Analgesic adjunct in general anaesthesia. Obstetrical analgesia.
Pethidine is a phenylpiperidine derivative opioid analgesic. It acts mainly as mu-receptor agonist. Like most, opioid analgesics, it mimics endogenous opioids by activating opioid receptors in the central and peripheral nervous system. It reduces the release of neurotransmitter substances and also reduces the activity of postsynaptic neurons in the spinal cord thus preventing transmission of pain impulse.
Pethidine hydrochloride may be administered by subcutaneous, intramuscular or slow intravenous injection. Pethidine Injection BP contains no antimicrobial agent. It should be used only once and any residue discarded. For intravenous administration the dosage should be decreased and the injection administered very slowly as a dilute solution. When pethidine is given parenterally, especially by the intravenous route, the patient should be lying down. While the subcutaneous route is suitable for occasional use, intramuscular administration is preferred for repeated doses. When administered intravenously, an opioid antagonist and facilities for assisted or controlled respiration should be immediately available during and following the injection. Adult Analgesia: 25 to 100 mg by SC or IM injection or 25 to 50 mg by slow IV injection every 3 to 4 hours The dose should be adjusted according to the severity of pain and the response of the patient. Dosage reduction may be necessary in the elderly. Premedication 50 to 100 mg by SC or IM injection or 25 to 50 mg by slow IV injection Obstetric analgesia 50 to 100 mg by SC or IM injection at intervals of 1 to 3 hours if necessary. Up to 3 doses may be given in 24 hours. Renal and Hepatic Dysfunction Dosage reduction and/or increased dosage intervals may be necessary in patients with renal or hepatic impairmen Paediatric Analgesia: 0.5 to 2 mg per kg bodyweight IM (maximum 100mg) every 3 to 4 hours. Premedication: 1 to 2 mg per kg bodyweight IM For tablet:Adults: For the relief of pain, Pethidine Tablets given in oral doses of 50 to 150 mg by mouth every 4 hours if necessary. Children: For the relief of pain, 1.1 to 1.76 mg per kg of body weight, not to exceed 100 mg every 3 to 4 hours as needed.
Increased pethidine metabolite levels with aciclovir, cimetidine, ritonavir. Reduced analgesic effects with phenytoin, barbiturates. Additive sedative and/or respiratory depressive effects with alcohol, barbiturates, benzodiazepines, phenothiazines, TCAs, other CNS depressants.
Hypersensitivity to pethidine. Patients who are taking or have taken a mono amine oxidase inhibitor (including selegiline) within the previous fourteen days. The combination of mono amine oxidase inhibitors and pethidine has caused hypotension, hypertension, excitation, rigidity, hyperpyrexia and/or convulsions, and in some cases fatalities have been reported. This combination should be avoided. Respiratory depression, or patients in whom respiratory reserve is significantly depleted (e.g. severe emphysema, severe chronic bronchitis, kyphoscoliosis, acute bronchial asthma, chronic airway disease). Convulsive states such as status epilepticus, tetanus and strychnine poisoning, due to the stimulatory effects of pethidine on the spinal cord. Similarly, pethidine should not be used in preeclampsia or eclampsia. Cardiac arrhythmias, especially supraventricular tachycardias; cor pulmonale. Pethidine has a possible vagolytic action which may produce a significant increase in the ventricular response rate. Diabetic acidosis where there is a danger of coma. Acute alcoholism or delirium tremens. Severe liver disease, incipient hepatic encephalopathy. Head injury, raised intracranial pressure (may cause diagnostic and monitoring problems; also hypercapnia associated with depressed respiration may increase intracranial pressure by itself); brain tumour.
More common Central Nervous System: Light headedness, dizziness, sedation, sweating, disorientation, bizarre feelings, hallucinations, psychosis. These effects seem to be more prominent in ambulatory patients and those not experiencing severe pain and may be relieved by reducing the dose slightly and lying the patient down. Gastrointestinal: nausea, vomiting, constipation. Less common Central Nervous System: Euphoria, dysphoria, weakness, headache, delirium, insomnia, anxiety, hyperactivity or agitation, convulsions or tremor, drowsiness, coma, vertigo, uncoordinated muscle movements, respiratory depression, cold clammy skin, pallor, visual disturbances, miosis, depression, mental clouding, occasional reports of mydriasis. Inadvertent injection around a nerve trunk may cause sensorineural effects, which is usually, but not always, transitory. Pethidine associated neurotoxicity (PAN) is a range of excitatory central nervous system effects including tremor, hallucinations, seizures and mood changes attributed to the metabolite norpethidine. As norpethidine is primarily cleared by renal excretion, pethidine should be used with caution in patients with impaired renal function, the elderly, the very young and in patients receiving concomitant therapy with drugs such as phenobarbital or phenylhydantoin. The problems of PAN are essentially dose-related. Gastrointestinal: Dry mouth, anorexia, biliary tract spasm. Genitourinary: Urinary retention, antidiuretic effect, anuria, reduced libido and/or potency. Cardiovascular: Facial flushing, vasodilation, tachycardia, bradycardia, palpitations, faintness, syncope, hypertension, hypotension, orthostatic hypotension, gangrene following inadvertent intra arterial administration. Dermatological: Hypersensitivity causing pruritus, urticaria and other skin rashes, erythema, oedema, pain at injection site, local tissue irritation and induration following subcutaneous administration (especially after repeated injection), fibrosis of muscle tissue with frequent repetition of intramuscular injection. Hepatic: Increased biliary tract pressure, choledochoduodenal sphincter spasm
Use in pregnancy ? Category C Opioid analgesics may cause respiratory depression in the newborn infant. These products should only be used during labour after weighing the needs of the mother against the risk to the foetus. Refer to PHARMACOKINETICS regarding pethidine and norpethidine levels in the foetus. Animal reproduction studies have not been conducted with pethidine hydrochloride and safe use in pregnancy prior to labour has not been established in respect to possible adverse effects on foetal development. Infants born of mothers who have been taking pethidine chronically may exhibit withdrawal symptoms. Use in lactation Pethidine appears in breast milk. As the concentrations in breast milk following usual therapeutic doses in the mother have not been determined and the clinical significance is not known, pethidine administration to nursing mothers is not recommended.
Symptoms: CNS/respiratory depression, mydriasis, bradycardia, pulmonary oedema, chronic tremor, CNS excitability, seizures.
Treatment: Symptomatic. Naloxone can be used to reverse opioid effects. Do not use naloxone for pethidine-induced seizures.
Store at room temperature. Do not freeze and protect from light.
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