Answer:
A - allopurinol
Step-by-step explanation:
- When one drug interacts with another at the level of metabolism, absorption or excretion then such interaction is known as Pharmacokinetic interaction.
- Due to these Pharmacokinetic interactions, the effect of the drugs administered together is different than when the drugs are administered individually.
- Concomitant use of allopurinol with azathioprine results in significantly increased azathioprine-induced toxicity as it shows significant pharmacokinetic interaction when administered with azathioprine.
- Therefore, it necessary to decrease its dosage.