Antimicrobials: cycloserine neuropsychiatric toxicity: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Antimicrobials: cycloserine neuropsychiatric toxicity

Sample item

A patient on a second-line regimen for drug-resistant tuberculosis develops depression, psychosis and a seizure two months into treatment. Which drug and which co-administered vitamin are associated with this problem?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Cycloserine with pyridoxine

Cycloserine is a neurotoxic second-line drug that causes depression, psychosis, anxiety and seizures. Pyridoxine is given with it, as with isoniazid, to lessen neurotoxicity. The other drugs are not typical causes of these central effects.

Option by option

  • A. Cycloserine with pyridoxine (correct)

    Correct. Cycloserine causes central neurotoxicity, and pyridoxine is given as prophylaxis.

  • B. Bedaquiline with pyridoxine

    Bedaquiline causes QT prolongation and nausea, not seizures and psychosis.

  • C. Ethambutol with riboflavin

    Ethambutol causes optic neuritis, and riboflavin is not the protective vitamin.

  • D. Pyrazinamide with folic acid

    Pyrazinamide causes hepatotoxicity and hyperuricaemia, not psychosis.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, Cycloserine with pyridoxine. Cycloserine is a neurotoxic second-line drug that causes depression, psychosis, anxiety and seizures.

Why is "Bedaquiline with pyridoxine" not the answer?

Bedaquiline causes QT prolongation and nausea, not seizures and psychosis.

Why is "Ethambutol with riboflavin" not the answer?

Ethambutol causes optic neuritis, and riboflavin is not the protective vitamin.

Why is "Pyrazinamide with folic acid" not the answer?

Pyrazinamide causes hepatotoxicity and hyperuricaemia, not psychosis.

What concept does this question test?

It tests Antimicrobials: cycloserine neuropsychiatric toxicity in Pharmacology. Pyridoxine is given with it, as with isoniazid, to lessen neurotoxicity. The other drugs are not typical causes of these central effects.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Antimicrobials: cycloserine neuropsychiatric toxicity?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.