drug interactions

Drug Interactions Review

Β Let’s talk drug-drug interactions πŸ’Š

🌟 With millions of potential drug interactions, figuring out what you need to commit to memory can be overwhelming 😡 . However, with the right approach and some (or a lotta πŸ˜†) practice, you’ll be able to see more of a pattern.


1. Know the interactions that are STRONG. πŸ’ͺ🏻 A strong inhibitor or inducer can lead to 5x the concentration of a drug while a weak inhibitor or inducer will cause less of a change. Higher concentrations lead to adverse side effects. Check out today’s post to help you remember the major inducers and inhibitors of CYP450 enzymes.

2. Know the interactions where the outcome is BAD. ❌ For example, tamoxifen is a prodrug. Strong 2D6 inhibitors such as fluoxetine, paroxetine, and bupropion can prevent the conversion of tamoxifen to its active form, therefore, increasing the risk that your patient will experience a reoccurrence of cancer. The same goes for the antiplatelet prodrug clopidogrel.

3. Start with the most COMMON drug interactions seen as they will likely be on exams and boards. πŸ“ Check out today’s post to see some examples of some of the major drug interactions.

4. Understand the MECHANISM of the drug interaction. 🧐 Inducers can ramp up the metabolism of a medication leading to decrease drug levels while inhibitors block the enzymes that break down the drug leading to higher drug concentrations.

CYP450 Enzymes, Major Inducers of

πŸ‘‰πŸ» Drugs that are inducers increase CYP450 enzyme activity by increasing enzyme synthesis. ⁠
πŸ‘‰πŸ» A drug also may be metabolized by the same CYP450 enzyme that it induces. Carbamazepine (Tegretol), a potent enzyme inducer, must be initiated at a low dose and then increased at weekly intervals as its half-life gradually decreases over time.⁠

CYP450 Enzymes, Major Inhibitors of

The CYP450 enzymes are essential for the production of numerous agents including cholesterol and steroids. Additionally, these enzymes are necessary for the detoxification of foreign chemicals and the metabolism of drugs.⁠
Drugs that are CYP450 inhibitors block the metabolic activity of one or more of the CYP450 enzymes. The extent to which an inhibitor affects the metabolism of a drug depends upon factors such as the dose and the ability of the inhibitor to bind to the enzyme.⁠