Which antibacterial would cause decreased sodium valproate concentration?

• A. Meropenem
• B. Amoxicillin
• C. Azithromycin
• D. Clarithromycin

Answer: (A)

The key idea is that certain antibiotics can dramatically lower valproate levels, risking loss of seizure control. Meropenem, a carbapenem, is well known for causing a rapid and substantial decrease in serum valproate within days of starting therapy. This happens because carbapenems disrupt the enterohepatic recirculation and promote gut degradation of valproic acid, leading to subtherapeutic concentrations.

Other antibiotics listed do not produce this effect. Amoxicillin is generally neutral regarding valproate levels, azithromycin has little impact, and clarithromycin tends to increase valproate levels by inhibiting its metabolism rather than decreasing them.

So, the antibiotic that would cause decreased sodium valproate concentration is meropenem. If such treatment is necessary, monitor valproate levels closely and adjust the dose or consider an alternative antibiotic if possible.