Chapter 4.1: Deadly Duos - Drug-Supplement (OTC) + Drug-Disease Interactions

how does st john’s wort interact with drugs?

• st john’s wort is a popular herb supplement used for mild depression

• most troublesome suppressor on shelf accessible (on PTCE)

• H acts as an enzyme induction → aggressively increases liver’s CYP450 enzyme system → body metabolizes and eliminates drugs much faster than intended → sub-therapeutic levels (under-dosing) of critical medicine

  • lowers oral contraceptives effectiveness

  • rejection in organ transplant patients by low cyclosporine levels

  • lowers efficacy of warfarin and HIV med

• interactions with st john wort’s medicine lowers drug effectiveness

what are the 4 Gs and Vitamin E’s effects on drugs?

• 4Gs: Garlic, Gingko Bilboa, Ginseng, and Ginger

  • they possess natural antiplatelet properties → thin blood

  • increases doses of vitamin E

• can be dangerous if patient is already taking anticoagulant like warfarin (coumadin) or clopidogrel (plavix)

  • the combo increases risk of internal bleeding

• patients are told to stop taking specific supplements at least 1 week prior to any surgical process to prevent excessive bleeding on operating table

how does iron and calcium interact with drugs?

• vitamin and minerals can also act as physical barriers to drug absorption

• calcium is found in antacids like Tums/supplements like Caltrate and Ferrous Sulfate which are powerful chelators

• both bind to antibiotics like tetracyclines and fluoroquinolones, preventing them from entering the blood stream

• both significantly interact with levothyroxine (synthroid)

  • if patient takes their thyroid medicine with a multivitamin or an iron supplement, the thyroid hormone binds to minerals and passes through the body unabsorbed

  • to avoid treatment failure, patients must separate their thyroid medicine from any vitamin by at least 4 hours

what is contraindication?

• medicine for one issue inadvertently worsens a separate, pre-existing medical condition

how do NSAIDS contraindicate hypertension/kidney failure?

• NSAIDs can pose a threat to patients with cardiovascular/renal disease

  • they work by constricting blood flow to kidneys and causing body to retain salt and water

• hypertension (HBP) or heart failure: extra fluid retention creates a “pressure cooker” → HBP and more strain on the heart

• chronic kidney disease: lowering blood flow by NSAIDs → acute renal failure

• if HBP/kidney patient asks for OTC pain reliever, recommend Tylenol

how do non-selective beta blockers contraindicate asthma?

• beta-blockers slows heart by blocking beta receptors

  • beta-1 is in heart

  • beta-2 is in lungs

• “cardio-selective” drugs like atenolol or metoprolol target heart (Beta-1) and are generally safe

• “non-selective” drugs like propranolol block both receptors

  • blocking beta-2 receptors in lungs → bronchoconstriction (tightening of airways)

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