Imipramine

How it works

It inhibits the reuptake of noradrenaline and serotonin at the synaptic cleft and also has antimuscarinic, antihistaminic and alpha-adrenergic blocking actions.

Prescribing in practice

• Tricyclic antidepressants are dangerous in overdose, causing cardiac arrhythmias, seizures and coma, so consider toxicity risk in patients at risk of self-harm and limit quantities supplied.
• Antimuscarinic and cardiovascular effects make it unsuitable in recent myocardial infarction, arrhythmias and severe cardiac disease, and it should be used with caution in the elderly.
• When used for enuresis in children, dosing must follow a children's formulary and avoid the doses used for depression.

Monitoring

Monitor mood, suicidal ideation (particularly early in treatment and in younger patients), cardiac status and antimuscarinic side effects.

Counselling the patient

• Explain that full antidepressant benefit may take several weeks.
• Do not stop the medicine abruptly, as withdrawal effects can occur.
• Report worsening mood, suicidal thoughts, palpitations or difficulty passing urine.

Evidence & guidelines

Imipramine is one of the original tricyclic antidepressants with long-established efficacy in depression; NICE recommends caution owing to its toxicity in overdose relative to newer agents.