Finasteride and dutasteride lower serum PSA by about half within six to twelve months. A man started on one for lower urinary tract symptoms who later has a PSA check will look reassuringly low unless the effect is accounted for.
Recording a baseline PSA before starting, noting the drug and start date on the record, and either doubling subsequent values or re-baselining after six months is established practice. Any confirmed rise in PSA while on treatment should prompt assessment.
- Check and record PSA before starting finasteride or dutasteride.
- Note the drug and start date on the problem list.
- Re-baseline PSA at about six months, or double values when comparing with earlier results.
- Investigate any confirmed PSA rise while on treatment.
Why it matters
An unadjusted PSA on these drugs can hide a rising cancer.
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