A case of denosumab-induced hypocalcaemia in a patient with non-metastatic prostate cancer and renal impairment

Denosumab is an emerging new treatment for osteoporosis in postmenopausal women and men with non-metastatic prostate cancer. It is largely used by specialists as an alternative treatment in patients with contraindications to traditional, more commonly used drugs such as bisphosphonates. One important side effect is hypocalcaemia, which may be life threatening. The risk of this is increased in renal impairment, mainly if eGFR < 30 ml/min/1.73m(2), and is exacerbated by vitamin D insufficiency. This is a case study of prolonged symptomatic hypocalcaemia after a single dose of denosumab in a patient with non-metastatic prostate cancer and moderate renal impairment (eGFR 40 ml/min/1.73m(2)). The patient presented with acute confusion, muscle cramps and myoclonic jerks 5 weeks after treatment. This case demonstrates the need to be aware of adverse effects of denosumab in mild-moderate renal impairment and the need to monitor calcium levels pre- and post-treatment.