A 53-year-old man with depression on citalopram 40mg daily is newly prescribed naproxen 250mg three times daily for gout. What is the most likely consequence of this drug interaction?

A 53-year-old man with depression on citalopram 40mg daily is newly prescribed naproxen 250mg three times daily for gout. What is the most likely consequence of this drug interaction?

• A. Increased risk of liver injury
• B. Increased risk of bleeding
• C. Serotonin syndrome
• D. Nephrotoxicity

Answer: (B)

The interaction raises bleeding risk. Citalopram is an SSRI that reduces the amount of serotonin taken up by platelets, leading to impaired platelet aggregation and a higher tendency to bleed. Naproxen, an NSAID, inhibits COX-1 and prostaglandin production, which also impairs platelet function and irritates the gut lining, increasing the likelihood of gastrointestinal bleeding. Together, they have an additive effect on bleeding risk, more than either alone. This explains why increased bleeding is the most likely consequence. Serotonin syndrome is not expected with naproxen, and while NSAIDs can affect the kidneys or cause liver injury in some cases, the combination with an SSRI specifically heightens bleeding risk.

The interaction raises bleeding risk. Citalopram is an SSRI that reduces the amount of serotonin taken up by platelets, leading to impaired platelet aggregation and a higher tendency to bleed. Naproxen, an NSAID, inhibits COX-1 and prostaglandin production, which also impairs platelet function and irritates the gut lining, increasing the likelihood of gastrointestinal bleeding. Together, they have an additive effect on bleeding risk, more than either alone. This explains why increased bleeding is the most likely consequence. Serotonin syndrome is not expected with naproxen, and while NSAIDs can affect the kidneys or cause liver injury in some cases, the combination with an SSRI specifically heightens bleeding risk.