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Table 2 Most common interacting pairs prevalence, risk rating, severity, reliability rating, predicted impact on the clinical outcome, and patient management

From: Prevalence of drug–drug interactions in geriatric patients at an ambulatory care pharmacy in a tertiary care teaching hospital

Interacting pair Prevalence (%) Risk rating Severity Reliability rating Predicted impact on the clinical outcome Patient management
Atorvastatine + omeprazole 25.16 C Major Poor Proton pump inhibitors may increase the serum concentration of HMG-CoA reductase inhibitors Monitor for evidence of rhabdomyolysis and other adverse effects if a PPI and an HMG-CoA reductase inhibitor are co-administered
Atorvastatin + calcium 22.90 C Minor Fair Antacids may decrease the serum concentration of HMG-CoA reductase inhibitors Monitor for decreased effects of statins (e.g., cholesterol changes) in patients who consistently take antacids concomitantly
Aspirin + calcium 17.09 B Minor Excellent Antacids may decrease the serum concentration of salicylates Monitor for decreased therapeutic effects of salicylates if an antacid is initiated/dose increased or increased effects if an antacid is discontinued/dose decreased
Aspirin + metformin 16.77 C Moderate Fair Salicylates may enhance the hypoglycemic effect of blood glucose lowering agents Monitor for excessive pharmacological effect (e.g., hypoglycemia). This is likely more of a concern in patients receiving salicylates at a dose of 3 g or greater per day
Aspirin + insulin 13.87 C Moderate Fair
Aspirin + gliclazide 12.25 C Moderate Fair
Amlodipine + calcium 11.29 C Moderate Excellent Calcium salts may diminish the therapeutic effect of calcium channel blockers Monitor the therapeutic effects of calcium channel blockers if a calcium supplement is initiated or dose changed
Gliclazide + omeprazole 10.64 C Moderate Fair CYP2C9 inhibitors (moderate) may decrease the metabolism of CYP2C9 substrates Monitor for increased effects of the CYP substrate if a CYP inhibitor is initiated/dose increased and decreased effects if a CYP inhibitor is discontinued/dose decreased
Atorvastatin + esomeprazole 10.32 C Major Poor Proton pump inhibitors may increase the serum concentration of HMG-CoA reductase inhibitors Monitor for evidence of rhabdomyolysis and other adverse effects if a PPI and an HMG-CoA reductase inhibitor are co-administered
Atorvastatin + clopidogrel 10.32 B Moderate Good Atorvastatin may diminish the antiplatelet effect of clopidogrel No action required
Calcium + gliclazide 9.03 B Minor Onset Rapid Excellent Antacids may increase the absorption of sulfonylureas. Increase in rate, not extent Monitor for increased therapeutic effects of sulfonylureas if an antacid is administered concomitantly. Consider separating doses by at least 2 h to minimize effects
Aspirin + multivitamins/minerals 8.38 C Moderate Fair Multivitamins/minerals (with AE, no iron) may enhance the antiplatelet effect of aspirin Monitor patients closely for evidence of increased platelet inhibition (e.g., bruising, bleeding)
Alendronate + calcium 7.74 D Moderate Fair Calcium salts may decrease the serum concentration of bisphosphonate derivatives Avoid administration of oral calcium supplements 30 min after alendronate
Amlodipine + tamsulosin 7.41 C Moderate Excellent Alpha1-blockers may enhance the hypotensive effect of calcium channel blockers Monitor for increased risk of hypotension during concomitant use of an alpha1-blocker and a calcium channel blocker
Calcium + levothyroxine 7.41 D Moderate Fair Calcium salts may diminish the therapeutic effect of thyroid products Separate the doses of the thyroid product and the oral calcium supplement by at least 4 h. Monitor the therapeutic effects of thyroid products if an oral calcium supplement is initiated or dose changed
Atorvastatin + carvedilol 7.09 C Moderate Fair P-glycoprotein/ABCB1 inhibitors may increase the serum concentration of P-glycoprotein/ABCB1 substrates. It may also enhance the distribution of p-glycoprotein substrates to specific tissues Monitor the effects of P-glycoprotein (Pgp) substrates if a Pgp inhibitor is started or if the dose of a concurrently used Pgp inhibitor changed