Which second-line TB agent is associated with CNS side effects including seizures and psychosis and may require baseline and ongoing monitoring?

• A. Cycloserine
• B. Ethionamide
• C. Capreomycin
• D. Streptomycin

Answer: (A)

Cycloserine stands out because of its well-known central nervous system toxicity, which can manifest as seizures and psychosis. Because of this risk, patients need baseline neuropsychiatric assessment and regular monitoring during treatment. The CNS effects are dose-related and can be worsened by renal impairment or preexisting psychiatric conditions, so monitoring typically includes watching for mood changes, anxiety, agitation, confusion, or new or worsened seizures, and adjusting the dose or stopping the drug if these occur. In addition to neuro monitoring, renal function should be checked since the drug is eliminated by the kidneys, with dose adjustments as needed. Other second-line TB drugs listed have different primary toxicities—ethionamide more often causes GI upset and hepatotoxicity, while capreomycin and streptomycin are mainly known for nephrotoxicity and ototoxicity—so seizures and psychosis are most characteristically linked to cycloserine.