ABSTRACT
Tetracyclics • As above • As above, but fewer side effects and interactions than with the tricyclic antidepressants
Monoamine oxidase inhibitors
• Prevent breakdown of norepinephrine, serotonin, and dopamine throughout body
• Can be discontinued 2-3 weeks before surgery and medication changed, or continued and drug interactions avoided
• Increased norepinephrine available in peripheral nerve endings
• Patients very sensitive to indirectly acting sympathomimetic drugs (ephedrine, metaraminol) which produce hypertension and adrenergic crises; direct-acting sympathomimetics are still dangerous but less so than indirectly acting agents
• Pethidine interacts to produce hypertension, rigidity, convulsions, restlessness, and hyperpyrexia
• Morphine and dihydrocodeine are safe
• Potentiation of effects of barbiturates, hypnotics, and other opioids; titrate these drugs carefully
Phenothiazines Butyrophenones
• Main therapeutic effect is antidopaminergic
• Can cause dysphoria in normal people
• Dermatological reaction in 5%
• Action also elevates • Rarely obstructive jaundice and blood
• Rarely, neuroleptic malignant syndrome
• Some anticholinergic and anti-adrenergic actions
• Potentiate opioids, hypnotics, benzodiazepines (note ventilatory effects)
• Antiemetic • Can have additive effects with atropine or hyoscine
• Peripheral a-blockade • ‘Main side effects: hypotension, sedation, and extrapyramidal symptoms
• Also adynamic ileus, glaucoma, urinary retention, agitation, confusion
• Synergistic with other anticholinergics
Benzodiazepines • Via benzodiazepine receptors
• Potentiation of all opioid and hypnotic drugs
• Additive effect with competitive neuromuscular blocking agents
Drug abuse is a world-wide problem and a multi-billion dollar illicit industry. People who are drug and substance abusers pose a number of problems for anaesthetists related to
• the effects of the drugs; • attendant infections (HIV hepatitis B); • medicolegal considerations.
