Which second-line anti-TB drug is contraindicated in patients with seizure disorders?

Cycloserine is the second-line anti-TB drug contraindicated in patients with seizure disorders due to its potential to lower the seizure threshold. This means that the drug can make it easier for seizures to occur in susceptible individuals. Cycloserine can also cause neuropsychiatric side effects, including confusion and seizures, which can exacerbate the condition of patients who already have seizure disorders.

In contrast, the other options do not have this specific contraindication related to seizures. Clofazimine, although it can have side effects, is primarily associated with skin discoloration and gastrointestinal symptoms rather than seizures. Delamanid is another second-line agent that has a different mechanism of action and is not directly linked to causing seizures. Isoniazid, while it can affect the nervous system and is associated with seizure risk in some cases when combined with certain other drugs, is not classified as a second-line anti-TB drug in this context. Therefore, Cycloserine's specific association with seizures makes it the correct choice regarding contraindications for patients with seizure disorders.