Common drugs with uncommonly known fatal drug - drug interatction

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30 Jun 2016 - General

I will like to create a post with everyone to share some common drug drug interaction that we encounter in our work. Sometimes, patients come with so many medications, I just got so worried that an additional prescription will cause some severe drug drug interaction. I find this MIMS site extremely helpful. When I encounter any patient with polypharmacy, I will make sure I search mims on any medication I want to prescribe and focus on potential fatal drug -drug interatction.  If the patient suffers any advserse side effect from a drug, it may be defensible. However, if we prescribe a medication with a known fatal drug drug interatction with another medication the patient is already on, we will be very much liable to a negligent lawsuit. Has anyone got any commonly prescribed drugs causing  not so uncommon fatal drug - drug interatction? 

Acne: Tetracycline class antibiotics + Isotretinoin -> Pseudotumor cerebri

Hyperlipidemia + infection: Clarithromycin + simvastatin -> Rhabdomyolysis

Contraception + Infection: Antibiotics + Oral contraception -> Reduced OCP absorption ( I find this fatal because if a couple is is terminate an unwanted pregnancy, we have a fatality )

IHD with ED : Viagra + nitrates -> Severe hypotension due to 2 vasodilators

Please add to the list : )



Patients on warfarin are often advised to choose acetaminophen for analgesia because nonsteroidal anti-inflammatory drugs (NSAIDs) can increase the risk for gastrointestinal bleeding. The interaction between warfarin and acetaminophen has been a well-kept secret. Many prescribers are unaware of the substantial data showing that regular use of acetaminophen increases the international normalized ratio (INR). Patients on warfarin should be monitored closely, and an INR should be obtained 3-5 days ...
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Trimethoprim/sulfamethoxazole (TMP/SMX) is an important potential cause of hyperkalemia in elderly patients and those with chronic kidney disease, especially with concomitant use of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs).With the emergence of community-acquired methicillin-resistant Staphylococcus aureus, and escalating fear about this pathogen, prescriptions for TMP/SMX are on the rise. The trimethoprim component acts like amiloride (a potassium...
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Clarithromycin with calcium channel blocker. Coadministration of clarithromycin with vasodilating calcium-channel blockers, such as amlodipine and felodipine, can cause hypotension and acute renal failure. Clarithromycin impairs the action of nifedipine by inhibiting CYP3A4 metabolism, resulting in hypotension—a serious but underappreciated risk.Other macrolides may also precipitate this interaction when given concomitantly with calcium-channel blockers, including erythromycin. Azithromycin, whi...
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