A pharmacist reviews a patient's medication list and finds they are taking warfarin and newly prescribed trimethoprim-sulfamethoxazole. What assessment finding warrants immediate follow-up?
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A
Increased bleeding risk due to CYP2C9 inhibition elevating warfarin levels
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B
Decreased warfarin efficacy due to enzyme induction
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C
Reduced renal clearance of trimethoprim only
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D
Additive antiplatelet effects unrelated to INR