An effect of lithium?

A patient presents with a complicated medical history, including nocturnal enuresis that has failed to respond to treatment.

Gerry is a 49-year-old disability support pensioner who presents for review of thirst, polyuria and polydipsia that has been present for several years. He reports needing to urinate every 1-2 hours during the day. He developed nocturnal enuresis six years ago and has been using a pad at night since. He has no associated dysuria. There is no history of childhood bedwetting, UTI or urinary disorder.

He has previously been given a trial of imipramine 50mg nocte for nocturnal enuresis, with no significant relief.