Drug Interactions Review
Let’s talk drug-drug interactions 💊
🌟 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 😆) practice, you’ll be able to see more of a pattern.
✨ TIPS FOR SUCCESS: ✨
1. Know the interactions that are STRONG. 💪🏻 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. 📝 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.
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Test your knowledge and check your answers on the second slide.
Lithium is a common ‘mood stabilizer’ used to treat the manic episodes of bipolar disorder, a mood disorder that is characterized by episodes of mania, hypomania, and depression. ⠀
The exact cause of bipolar disorder is unknown but is highly linked to family history, genetics, and abnormalities in neurotransmitters. This makes it tricky to pinpoint exactly how lithium works to treat bipolar but there are many proposed mechanisms of action. ⠀
Whenever you see the medication lithium, always think SALT as lithium (Li+) is located close to sodium (Na+) on the periodic table and they share similar structures. Because of this, lithium levels are often affected by salt and water balance as well as renal function (excreted mainly through kidneys). ⠀
Dehydration can cause lithium levels to increase while increasing sodium intake can cause lithium levels to decrease. Medications that affect water and salt balance (ex: diuretics, NSAIDs, ACEI) can also alter lithium concentrations. ⠀
The starting dose of lithium is 300 mg two or three times a day (The brand name is Lithobid to help you remember that it can be given BID or twice daily)⠀
Lithium is considered teratogenic due to the potential for fetal cardiac defects. The risks and benefits should be discussed with a healthcare provider before starting it in women of childbearing age.⠀
Major depressive disorder (MDD) is a mood disorder characterized by persistent feelings of sadness and loss of interest that interferes with normal daily functioning.
Because of this, the drugs developed to treat MDD selectively target the reuptake of serotonin and norepinephrine, increasing levels of these neurotransmitters in the synapse and enhancing NT signaling.