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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