Which medication is most likely responsible for causing Stevens-Johnson syndrome in a patient with multiple medical conditions?

Allopurinol is well-known for its association with Stevens-Johnson syndrome (SJS), a severe reaction that can result in life-threatening skin and mucous membrane conditions. This medication, commonly prescribed for the management of gout and certain types of kidney stones by reducing uric acid levels, has been documented in multiple studies and case reports as having a significant risk for developing SJS, particularly when used in high doses or in patients with renal impairment.

The onset of SJS can occur after starting allopurinol, and the condition is characterized by flu-like symptoms followed by painful blisters and skin shedding. The risk is notably higher in certain populations, including patients who carry specific genetic markers, especially in Asian populations where HLA-B*5801 allele screening is recommended prior to initiation of therapy.

In contrast, while the other medications listed can have side effects and risks associated with them, they are not commonly linked to Stevens-Johnson syndrome to the same extent as allopurinol. Thus, understanding these connections aids in recognizing the potential adverse effects of medications in patients with multiple medical conditions, making allopurinol the medication most likely responsible for causing SJS in this scenario.