Drug Interaction Report

MONITOR: Agents that cause urinary alkalinization can reduce serum salicylate concentrations in patients receiving anti-inflammatory dosages of aspirin or other salicylates. The mechanism involves reduction in salicylate renal tubular reabsorption due to increased urinary pH, resulting in increased renal salicylate clearance especially above urine pH of 7. This interaction is sometimes exploited in the treatment of salicylate toxicity.

MANAGEMENT: Patients treated chronically with urinary alkalinizers and large doses of salicylates (i.e. 3 g/day or more) should be monitored for potentially diminished or inadequate analgesic and anti-inflammatory effects, and the salicylate dosage adjusted if necessary.

MONITOR: The safety and efficacy of collagenase clostridium histolyticum in patients currently receiving, or within 7 days of receiving, anticoagulant medications other than low-dose aspirin (e.g., up to 150 mg/day) is unknown. Theoretically, the risk of bleeding complications may be increased. In clinical trials, 70% of collagenase clostridium histolyticum-treated patients developed an ecchymosis/contusion and 38% developed an injection site hemorrhage.

MANAGEMENT: Collagenase clostridium histolyticum should be used with caution in patients receiving or within 7 days of receiving anticoagulants (except for low-dose aspirin), platelet inhibitors, or thrombolytic agents.

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.

One study has reported that coadministration of caffeine and aspirin lead to a 25% increase in the rate of appearance and 17% increase in maximum concentration of salicylate in the plasma. A significantly higher area under the plasma concentration time curve of salicylate was also reported when both drugs were administered together. The exact mechanism of this interaction has not been specified. Physicians and patients should be aware that coadministration of aspirin and caffeine may lead to higher salicylate levels faster.