Sulfasalazine Side Effects — SCE Rheumatology MCQ

Instant feedback + full explanation. One question, done properly.

EasyRheumatology PharmacologySulfasalazine Side EffectsSCE Rheumatology

A 52-year-old man with rheumatoid arthritis is undergoing fertility assessment. His semen analysis was normal before treatment, but four months after starting sulfasalazine it shows a reduced sperm concentration and reduced motility. What is the most likely explanation?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Reversible oligospermia caused by sulfasalazine

Sulfasalazine can impair male fertility by causing oligospermia, reduced sperm motility and abnormal sperm morphology. The effect is reversible: the UK SmPC states that sperm abnormalities generally resolve within 2–3 months after discontinuation. The normal pretreatment semen analysis and subsequent decline after several months of exposure support a drug effect rather than rheumatoid arthritis, hypogonadism or age-related change. Sulfasalazine can interfere with certain biochemical laboratory assays, but this does not explain a genuinely reduced sperm concentration and motility. Permanent azoospermia is not the characteristic effect. If fertility is clinically affected, treatment should be reviewed and any change to rheumatoid arthritis therapy individualised rather than automatically substituting a potentially unsuitable DMARD.

Reference: Pfizer Limited. Sulfasalazine 500 mg Tablets, Summary of Product Characteristics, sections 4.4 and 4.8; updated 2025. https://www.medicines.org.uk/emc/product/15886/smpc