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Table 2 The most common potential clinically relevant drug-to-drug interactions (DDIs) in 99 older patients discharged from hospital to home care

From: Potential drug-to-drug interactions: a cross-sectional study among older patients discharged from hospital to home care

Drug-to-drug interaction (ATC code)

Example of drug combinations

Number of patients

Mechanism of interaction

Potential precautions or handling of the drug-to-drug interaction

Alendronate (M05B A04)–calcium carbonate/vitamin D3 in combination (A12A X-)

Fosamax®–Calcigran Forte®

16

When taken simultaneously per os, calcium-containing drugs may decrease the absorption of peroral bisphosphonates.

Bisphosphonates should be taken at least 1 h before or 2 h after the calcium-containing drugs. For drugs containing more than 1000 mg of calcium, bisphosphonates should be taken at least 3 h before calcium.

Warfarin (B01A A03)–paracetamol (N02B E01)

Marevan®–Paracet®

14

Paracetamol may reduce the concentration of some coagulation factors and increase the effect of warfarin, with an increase in INR. The use of 1 g paracetamol 4 times per day for 3–4 days consecutively increased INR with a mean of 0.5 units.

Monitor INR during concomitant use. The use of paracetamol in combination with warfarin is far safer than using for example. NSAIDs when analgesics are required.

Digitalis glycosides (C01A)–high-ceiling diuretics (C03C)a

Digitoxin®–Furix®

12

Loop-diuretics may result in hypokalemia and consequently lead to an increased toxicity of digitoxin, although its blood concentrations remain unchanged.

Monitor blood potassium concentration.

Warfarin (B01A A03)–prednisolone (H02A B06)

Marevan®–Prednisolon®

12

Unclear mechanism. INR may increase when combining warfarin with high-dose glucocorticoids.

Monitor INR and adjust warfarin dosage.

Benzodiazepine-related drugs (N05C F)–opioids (N02A)a

Zopiclone®–OxyNorm®

11

Increased sedative effects. Sporadic combination of the drugs is acceptable.

Clinical monitoring for sedative effects. Special consideration of this drug combination is required in frail, elderly patients with non-malign pain.

Warfarin (B01A A03)–allopurinol (M04A A01)

Marevan®–Zyloric®

10

Unclear mechanism. Allopurinol may inhibit the metabolism of warfarin in some individuals and thereby increase the effect of warfarin, and INR.

Monitor INR and adjust warfarin dosage.

  1. All DDIs were classified as moderate (drugs may be combined but precautions must be taken) according to the Norwegian database www.interaksjoner.no. The description of mechanism and possible precautions and handling is also based on this database
  2. INR international normalized ratio, NSAIDs non-steroidal anti-inflammatory drugs
  3. aThese interactions are described on a higher level of ATC codes involving several active substances
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Safety in Health

ISSN: 2056-5917

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