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Antidepressants, Tricyclics and Related Drugs
Fichas del conjunto (4)
- 1Give eg's of & indications for tricyclics.eg's: amitriptyline, lofepramine
Indications:
• Moderate-to-severe depression - where 1st line SSRI's are ineffective
• Neuropathic pain- not licensed for this indication - 2MOA of tricyclics.Tricyclic antidepressants inhibit neuronal reuptake of serotonin (5-HT) & noradrenaline from the synaptic cleft, thereby increasing their availability for neurotransmission. This appears to be the mechanism by which they improve mood & physical Sx in moderate-to-severe (but not mild) depression & probably accounts for their effect in modifying neuropathic P.
Tricyclic antidepressants also block a wide array of receptors, including muscarinic, histamine (H1), α-adrenergic (α1 and α2) and dopamine (D2) receptors. This accounts for the extensive adverse effects profile that limits their clinical utility. - 3SE's of tricyclics.• Blockade of antimuscarinic receptors causes dry mouth, constipation, urinary retention & blurred vision
• Blockade of H1 & α1 receptors causes sedation & hypotension
• Arrhythmias
• ECG changes - inc prolongation of the QT & QRS durations
• Convulsions
• Hallucinations
• Mania
• Blockade of dopamine receptors can cause breast changes & sexual dysfunction & rarely causes extrapyramidal symptoms (tremor & dyskinesia)
• Extremely dangerous in OD - can cause hypotension, arrhythmias, convulsions, coma, resp failure, death
• Sudden withdrawal - GI upset, neurological & flu like Sx, sleep disturbance - 4CI's, cautions, & important interactions of tricyclics.CI's:
• Should not be given with MAOI's
Cautions:
• Elderly
• CVD
• Epilepsy
• Constipation
• Prostatic hypertrophy
• Raised intraocular pressure
Important interactions:
Tricyclic antidepressants should not be given with monoamine oxidase inhibitors as both drug classes increase serotonin & noradrenaline levels at the synapse & together they can precipitate HT & hyperthermia or serotonin syndrome (see Antidepressants, selective serotonin reuptake inhibitors). Tricyclic antidepressants can augment antimuscarinic, sedative or hypotensive adverse effects of other drugs.