LETTER TO THE EDITOR: Finasteride: a steroid-unsparing drug?
PDF: 171.66.120.158/cgi/reprint/38/3/285b
A 63-yr-old man presented with stiffness of the shoulders and a history of eczema; examination was normal. The erythrocyte sedimentation rate (ESR) was 90 mm/h and polymyalgia rheumatica (PMR) was diagnosed. Prednisolone produced a rapid improvement and 10 months later, on 10 mg, the ESR was 28 mm/h.
Finasteride 5 mg daily was given for benign prostatic hyperplasia and 3 months later polymyalgia worsened, eczema recurred and the ESR rose to 54 mm/h. After discontinuing finasteride, the symptoms resolved, and the ESR fell.
He recommenced finasteride 3.5 yr later with the same pattern of a delayed exacerbation and frise in ESR; if he took prednisolone in the morning and finasteride in the evening, the interaction was abolished. Most recently, the ESR was 19 mm/h.
Finasteride is an inhibitor of 5 alpha-reductase and causes improvements in symptoms of benign prostatic hyperplasia. It is metabolized by the cytochrome P450 system with a half-life of 4.7–7.1h.
Pharmacological induction of hepatic microsomal enzymes may cause relapse of steroid-dependent diseases, and enzyme induction by finasteride may be a mechanism of interaction.
However, the manufacturers [Merck] state that there are no reports of induction of the P450 system, and finasteride has no effect on the serum levels of adrenal steroids.
Furthermore, the patient noted that delaying ingestion of steroid beyond two finasteride half-lives abolished the interaction, suggesting a more acute effect. A less likely explanation is that finasteride induces PMR and eczema. Reversible myopathy has been described.
The Committee on the Safety of Medicines (personal communication) has received no other reportsof exacerbation of PMR or eczema associated with finasteride.
The Committee has, however, received a single report of a 69-yr-old man whose rheumatoidated arthritis flared up 2 months after starting the drug and settled when it was withdrawn.
We have reported a 63-yr-old male with well controlled PMR and eczema in whom both diseases became more active following the introduction of finasteride. Mechanisms of this apparent interaction deserve further study.
M. PERSEY, L. PAYNE, M. WEBLEY
Departments of Rheumatology and Pharmacy, Stoke
Mandeville Hospital, Mandeville Road, Aylesbury, Bucks.
HP21 8AL, UK
Accepted 16 October 1998