To the Editor: Thalidomide has recently been approved for use in treating recurrence of erythema nodosum leprosum and multiple myeloma after failure of standard therapies. Common side effects of thalidomide treatment include drowsiness, sedation, rash and paraesthesiae.1 Dizziness, hypotension and bradycardia occur less commonly.1-3 Of 91 patients treated with thalidomide (80 with multiple myeloma), we have had one case of symptomatic bradycardia. We describe this patient, who was able to continue treatment on a reduced dose of thalidomide.

A 71-year-old woman, with a history of breast cancer (treated with radiotherapy and tamoxifen), arthritis, crush fractures, and hip and knee replacement, was diagnosed with multiple myeloma. She was prescribed intravenous pamidronate 90 mg every month and oral therapy with melphalan, but she experienced haematological toxicity and the melphalan was stopped.

After progression of the disease, 100 mg of thalidomide was commenced at night, with the aim of increasing the dose by 100 mg every fortnight until a response was achieved. Three weeks later, the patient presented to hospital for pamidronate infusion complaining of a 2-week history of shortness of breath, especially on exertion. There was no oedema present, and her blood pressure was 135/70 mmHg. Electrocardiography showed sinus bradycardia, with a heart rate of 46 beats/min. The dose of thalidomide had been titrated to 200 mg at night.

Thalidomide was stopped, and the patient was referred to a cardiologist, who performed an echocardiogram, 24-hour Holter monitoring and a stress test. The results from these tests showed no underlying cardiac disease or abnormalities.

Six weeks later, on review, the bradycardia had resolved (heart rate, 60 beats/min). Thalidomide was recommenced at 100 mg daily. However, after a further 6 weeks, her heart rate had decreased again to 45 beats/min, and the dose of thalidomide was reduced to 100 mg on alternate days.

Thalidomide therapy has been continued in this patient at 100 mg on alternate days. Her heart rate has stabilised between 50 and 55 beats/min, and she has remained asymptomatic. The multiple myeloma is responding to treatment, as indicated by symptom control and serial measurements of IgG kappa. She continues to take hydroxychloroquine, rofecoxib and sertraline.

Bradycardia is a rare side effect of thalidomide therapy, with an incidence of 0.12%.1,2 The mechanism is unknown, but could be related to thalidomide’s central sedative effect.1 There are isolated published case reports of thalidomide-induced bradycardia; in all cases the drug was stopped.2-5

Thalidomide is being used for various conditions for which no alternative therapy exists. As the drug is now commercially available in Australia, its use is likely to increase. In all patients taking thalidomide, we recommend measuring heart rate; and in those with underlying heart disease, or who are taking medications that can precipitate bradycardia, we recommend electrocardiographic monitoring.

Our findings in this patient suggest that thalidomide-induced bradycardia can be successfully managed with dose reduction and regular monitoring.