Risedronate sodium

Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Actonel (Aventis Pharma)
5 mg film-coated tablets
Approved indication: osteoporosis, Paget's disease
Australian Medicines Handbook Section 10.4.2

Bisphosphonates inhibit the resorption of bone by osteoclasts. By reducing the turnover of bone and increasing bone density the bisphosphonates can help patients with Paget's disease or osteoporosis.

Like the other bisphosphonates, risedronate is poorly absorbed. The bioavailability of the tablet is only 0.63% and this is reduced by food. Patients should only take the tablets with water. After absorption risedronate is distributed to bone. Although half the absorbed dose is excreted within 24 hours the elimination of the drug from bone is slow. The half-life is approximately 20 days.

Patients must take the tablets while they are standing. They should remain upright for at least 30 minutes. This helps to ensure the tablet reaches the stomach and does not irritate the oesophagus. Approximately 12% of patients will complain of abdominal pain. Other adverse events reported in clinical trials include arthralgia, itching, flu-like symptoms, diarrhoea and dizziness.

Risedronate is approved for several indications. There is evidence from clinical trials to support each indication.