Finasteride: men taking finasteride for hair loss who experience depressive illness or suicidal thoughts should stop taking the drug immediately and seek medical help.

Clozapine: the MHRA says the anticholinergic properties of clozapine mean that patients on the antipsychotic are likely to suffer intestinal peristalsis. At its worst, intestinal obstruction, faecal impaction and paralytic ileus can occur – and in some cases have been fatal. Patients with constipation should seek prompt advice and treatment, with particular caution needed in anyone on any other medication that can cause the problem or has anticholinergic properties, has a history of colonic disease or lower abdominal surgery, or is aged 60 years or older.

Gabapentin has been associated with a rare risk of severe respiratory depression. Anyone who is taking the drug and experiences any trouble breathing should seek medical help.