15-Minute Pharmacology: Drug Interactions Matt Ozanich, MHHS, NRP Director of Pre-Hospital Care Trumbull Memorial Hospital

Disclaimer Always follow local protocols Always follow administrative policies Always do what is in the best interest of the patient

Objectives Define the categories of drug interactions Discuss examples of common drug interactions within each category.

General Physiology of Interactions Enzymes / Hormones Duplication Competition Similar Mechanisms Sensitivity

Drug Interactions Duplication Taking two medications with a similar ingredient Common examples OTC Sleep Aids with Cold Medicine Cold Medicine with OTC Pain Relievers

Drug Interactions Antagonism Competitive – binds to common receptor Non-competitive – alters binding site The idea is to minimize stimulation of the receptor Common Examples Naloxone and Opioids Romazicon and Benzos Beta Blockers and Albuterol

Drug Interactions Idiosyncratic Reactions Unique, strange, unpredicted reaction Typically associated with enzyme or hormone deficiencies Allergy / Anaphylaxis falls here Common Examples Soma (muscle relaxer) paralysis/blindness Aspirin causing an asthma attack Sulfa antibiotics causing skin burns

Drug Interactions Food Reactions Foods affect metabolism May block enzymes May prevent absorption Common Examples Milk inhibits tetracycline absorption Grapefruit juice intensifies benzos, estrogen, statins Tyramine + MAOIs = hypertensive crisis

Drug Interactions Synergism Combined action of two drugs Common Examples Sulfa + Trimethoprim = better bacteria killer Aspirin + Warfarin = spont. Hemorrhage Captopril + Nitro = enh. BP control in CHF

Drug Interactions Potentiation Combined action of two drugs “Enhanced” synergism

Synergism vs Potentiation 1 + 1 = 2 1 + 1 = 3

Drug Interactions Potentiation Combined action of two drugs “Enhanced” synergism Common Examples Benzos and Alcohol Benzos and Ketamine Opiates and Ketamine Clonidine and Timolol Warfarin and Amiodarone SMZ/TMP and Warfarin

Drug Interactions Patient Education Identify compliance with meds Emphasize importance of compliance Report compliance to facility Encourage compliance at home

Works Cited Ament, P. W., Bertolino, J. G., & Liszewski, J. L. (2000, March 15). Clinically Significant Drug Interactions. American Family Physician, 61(6), 1745-1754. Moini, J. (2012). Focus on Pharmacology: Principles for Health Professionals. Upper Saddle River: Pearson. Sener, S., Eken, C., Schultz, C., Serinken, M., & Ozsarac, M. (2011, February). Ketamine with and without midazolam for emergency department sedation in adults: a randomized controlled trial. Annals of Emergency Medicine, 57(2), 109-114. doi:10.1016/j.annemergmed.2010.09.010 Thi, L., Shaw, D., & Bird, J. (2009, March 24). Warfarin potentiation: a review of the "FAB-4" significant drug interactions. The Consultant Pharmacist, 24(3), 227-230.

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