Which drug is most likely contributing to confusion and anxiety in a woman with multidrug-resistant tuberculosis?

The correct choice is Cycloserine, which is known to cause neuropsychiatric side effects, including confusion and anxiety, particularly in susceptible individuals. This antibiotic, used in the treatment of multidrug-resistant tuberculosis, is a structural analog of the amino acid D-alanine and inhibits bacterial cell wall synthesis.

Cycloserine can cross the blood-brain barrier, and its effects on the central nervous system can lead to significant psychiatric symptoms, especially when the dosage is high or the patient has pre-existing mental health conditions. Symptoms can range from mild mood disturbances to severe anxiety and confusion, indicating its potential to contribute to these issues in patients.

In contrast, while the other drugs listed—such as Streptomycin, Pyrazinamide, and Ethionamide—are also used in tuberculosis treatment, they are not typically associated with neuropsychiatric side effects as commonly or as severely as Cycloserine is. For instance, Streptomycin primarily causes ototoxicity and nephrotoxicity, while Pyrazinamide can lead to hepatotoxicity and Ethionamide may cause gastrointestinal disturbances without directly leading to confusion and anxiety.