Drug Interactions and Contraindications

What medication does Warfarin interact with that increases bleeding risk (High INR)?

Bactrim, NSAIDs, and SSRIs

What medication decreases the effectiveness of Warfarin (Low INR)?

Carbamazepine, Rifampin, St. John’s Wort

What drug combination causes severe respiratory depression?

Opioids + Benzodiazepines

What drug combination causes hyperkalemia (high potassium levels)?

ACE Inhibitors/ARBS + Spironolactone

What drug combination causes risk of torsades de pointes?

Multiple QT Prolonging Drugs

What happens when you mix MAOIs with SSRIs, SSNRIs, or Tramadol?

Serotonin Syndrome

What happens if you combine PDE5 inhibitors with nitrates?

A sudden, fatal drop in blood pressure can occur

What happens if you mix Statins with Strong CYP3A4 inhibitors?

Rhabdomyolysis

A patient on Warfarin takes Bactrim, what happens to their bleeding risk?

It increases

What are the dangers of St. Johns Wort?

It makes certain drugs weaker

What are the dangers of Ginkgo and Fish Oil?

It thins blood so if mixed with anticoagulants or NSAIDs it increases bleeding risk

What are the dangers of Kava and Valerian?

They increase sleepiness so if mixed with benzodiazepines or alcohol it can make a person dangerously sedated

What happens when grapefruit is taken with certain medications?

If taken with medications such as statins and benzodiazepines they don’t get broken down properly and their levels increase dangerously

What happens when leafy greens are taken with certain medications?

If eaten a lot, it can interact with medications such as Warfarin, it can cancel it out

What happens when dairy is taken with certain medications?

When consumed with certain antibiotics, it can prevent them from being absorbed

How can biotin (B7) affect lab results?

It can give a falsely low troponin result and it can also mess up thyroid tests

How can beta blockers affect lab results?

It can hide the symptoms of hypoglycemia (low blood sugar)

How can Levadopa affect lab results?

It can cause a false glucose increasing, affecting insulin dosing

What medication can a patient with asthma not take?

Non selective beta blocker such as propranolol

What medication can a patient with heart failure not take?

NSAIDs, which make fluid retention worse

What medication can a patient with kidney disease not take?

Medications such as metformin

What medication can a patient who is pregnant not take?

ACE inhibitors, Statins, Warfarin etc.

What is the three step plan when identifying drug interactions?

1.) Identify a high risk drug combination 2.) stop filling and flag the Rx 3.) Immediately notify the pharmacist

You have a patient with a prescription for Sildenafil and Nitroglycerin, what is your first action?

Flag the prescriptions and alert the pharmacist