Metabolism

Drug Interaction

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Drug Interaction, Food Interaction, Food-Drug Interactions

  • See Also
  1. Drug-Drug Interactions in the Elderly
  2. Polypharmacy
  • Types
  1. Pharmacokinetic (most common)
    1. Two drugs compete for the same mechanism of absorption, distribution, metabolism or excretion (ADME)
    2. Results in a change in one or both drugs concentration at the site of their action when both agents are taken
    3. Typically involves Cytochrome P450, UGT, P-Glycoprotein or OATP
    4. Often drug dosage changes and monitoring are sufficient for low to moderate risk interactions
  2. Pharmacodynamic
    1. One drug directly blocks or exacerbates another drugs activity without modifying drug concentrations
    2. Offending drug, typically must be stopped (drug dosage modifications typically do not resolve interaction)
  • Causes
  • Food Interactions
  1. See Antibiotic Food Interactions
  2. See Grapefruit Interactions
  • Causes
  • Common Serious Drug-Drug Interactions
  1. Drugs with numerous interactions
    1. Warfarin Drug Interactions
    2. Direct Oral Anticoagulants
    3. HMG-CoA Reductase Inhibitor (Statins)
    4. Drug Interactions due to Chelating Cations
  2. Specific important drug-Drug Interactions
    1. Phosphodiesterase Inhibitor (e.g. Viagra) and Nitroglycerin (Hypotension)
    2. Beta Blockers and Clonidine (Hypertensive Crisis)
    3. ACE Inhibitors and Potassium supplements, Potassium-Sparing Diuretics or Septra (Hyperkalemia)
  3. Drug-Induced Syndromes (exacerbated by combinations of agents)
    1. Prolonged QT Interval due to Medication
    2. Serotonin Syndrome
    3. CNS Depressants
  • References
  1. Asher (2017) Am Fam Physician 96(2): 101-7 [PubMed]