Which NSAID is the only one listed in pure S form?

Which NSAID is the only one listed in pure S form?

• A. Ibuprofen
• B. Aspirin
• C. Naproxen
• D. Diclofenac

Answer: (C)

Chirality in NSAIDs and enantiomeric purity matter here. Many NSAIDs have a chiral center, giving two mirror-image forms, S and R, and the S form is often the more active one. Naproxen is marketed and used as the pure S enantiomer (S-naproxen), so it is supplied entirely in the S form. The others either aren’t chiral or are used as a racemate (a 50:50 mix of S and R), such as ibuprofen, while aspirin and diclofenac are not provided as a pure S form. So Naproxen is the only one listed that exists in pure S form.

Chirality in NSAIDs and enantiomeric purity matter here. Many NSAIDs have a chiral center, giving two mirror-image forms, S and R, and the S form is often the more active one. Naproxen is marketed and used as the pure S enantiomer (S-naproxen), so it is supplied entirely in the S form. The others either aren’t chiral or are used as a racemate (a 50:50 mix of S and R), such as ibuprofen, while aspirin and diclofenac are not provided as a pure S form. So Naproxen is the only one listed that exists in pure S form.