What is a key drug interaction to consider with INH?

The key drug interaction to consider with isoniazid (INH) involves phenytoin, as INH can increase phenytoin levels in the bloodstream. Isoniazid inhibits the enzyme responsible for the metabolism of phenytoin, leading to elevated levels of phenytoin and an increased risk of toxicity.

Phenytoin is a commonly used antiepileptic medication, and elevated levels can lead to side effects such as dizziness, ataxia, and potential more severe outcomes like Steven-Johnson syndrome. Therefore, it is critical for healthcare providers to monitor phenytoin levels closely when patients are started on INH, adjust dosages as necessary, and educate patients about the signs of phenytoin toxicity.

Considering the other options, while they raise valid points about drug interactions involving INH, they do not reflect the most clinically significant interaction as noted with phenytoin.