2 - Common Drug Interactions & Contraindications

Pro-Tip: Memorize these for higher PTCE scores.

Warfarin

Drug Interactions: NSAIDs, Antibiotics, Fish Oil, Coenzyme 10, Garlic Supplements, Ginko Biloba, Vitamin K

Side Effects: Excessive bruising / bleeding

Pregnancy Category: X

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs):

Drug Interactions: When taken with Lithium or Methotrexate, can cause toxicity

Interactions: Increased Risk of Bleeding with Coumadin (warfarin)

HMG-CoA Reductase Inhibitors (-statins)

Food Interaction: Grapefruit inhibits metabolism leading to muscle damage

Pregnancy Category: X

Benzodiazepines & Hydrocodone

Drug Interaction: Benzodiazepines and Hydrocodone, taken together, can cause respiratory depression

Pregnancy Category: D (Benzodiazepine)

Clopidogrel and PPIs

Drug Interaction: Clopidogrel and PPIs, when taken together can reduce effectiveness of Clopidogrel

Antibiotics

Drug Interaction: Increased risk of bleeding with Anticoagulants, reduce effectiveness of birth control

Pregnancy Category: varies, Doxycycline is Category D

Ace Inhibitor (ACEi)

Pregnancy Category: D

Serotonin Syndrome

Drug Interaction: SSRIs or SNRIs and MAOIs, taken together, can cause Serotonin syndrome

Digoxin & Diuretics

Drug Interaction: Digoxin and Diuretics, taken together, can cause increased risk of Digoxin toxicity

Lithium

Drug Interactions: Alcohol, NSAIDs, and Methotrexate should be avoided when taking Lithium

Pregnancy Category: D

Disclaimer: This is not an exhaustive list. This is “minimum” necessary knowledge related to this knowledge domain. If you focus on learning this information well, you will perform well on this section of the exam. If you look up information on a given drug, you will see a seemingly endless array of side effects, interactions, warnings, and precautions. Fortunately, you aren’t expected to know all of this information for each medication.