Lithium × Magnesium (oral salts: citrate, glycinate, oxide, sulfate)

Magnesium theoretically antagonises lithium-driven neuronal excitability, but no clinical cases of efficacy loss at standard magnesium doses (up to 400 mg/day) have been described.

The combination usually causes no specific symptoms. Each drug's individual side effects remain.

No dose adjustment needed. On stable lithium dose, monitor levels on the usual schedule. Higher magnesium doses (over 1 g/day) are discussed separately — hypermagnesaemia risk in chronic kidney disease.