PURPOSE Amiodarone hydrochloride is an iodine-rich drug effective in the control of various tachyarrhythmias. It is known to cause refractory to thyrotoxicosis, which usually does not respond to regular antithyroid drugs. Lithium bicarbonate is a medication used to treat psychiatric disorders; it also influences thyroid production and release of hormones. We tried it in combination with propylthiouracil (PTU) for the treatment of amiodarone-induced thyrotoxicosis. PATIENTS AND METHODS Twenty-one patients were studied. The first group (n = 5) was treated by amiodarone withdrawal only. The second group (n = 7) received PTU (300 to 600 mg), and the third (n = 9) PTU (300 mg) and lithium (900 to 1350 mg) daily. Patient selection was not randomized. The PTU + lithium group had more severe symptoms and signs of thyrotoxicosis, as well as thyroxine levels at least 50% above the upper limit of normal. They also had been on a longer course of amiodarone treatment (34.3 +/- 11.9 months) than the PTU-only (11.4 +/- 7.5) and the no-treatment (7.8 +/- 4.2) groups. RESULTS While there was no difference between the first two groups in time until recovery (10.6 +/- 4.0 versus 11.6 +/- 0.5 weeks, respectively), the group receiving lithium normalized their thyroid function tests in only 4.3 +/- 0.5 weeks (P < 0.01 versus both other groups). T3 levels normalized even earlier-by 3 weeks of lithium treatment. No adverse effects of lithium were encountered, and the medication was stopped 4 to 6 weeks after achieving a normal clinical and biochemical state. CONCLUSIONS We conclude that lithium is a useful and safe medication for treatment of iodine-induced thyrotoxicosis caused by amiodarone. We would reserve this treatment for severe cases only. Further studies are needed to find out whether in patients with this troublesome complication lithium therapy could permit continuation of amiodarone treatment.