Clinical Pharmacy: Drug Interactions

Study Notes

PPI therapy is required with aspirin and P2Y12 receptor inhibitors to prevent gastric bleeding.
Omeprazole (PPI) inhibits CYP2C19, which is involved in the biotransformation of clopidogrel, increasing the risk of stent thrombosis.
Concomitant use of omeprazole and clopidogrel increases the risk of stent thrombosis.

ACEI increases insulin secretion, which affects glimepiride.
Macrolides displace sulfonylurea from its protein-bound state, leading to increased serum-free levels and causing hypoglycemia.
Macrolides are P-glycoprotein inhibitors, reducing the efflux of sulfonylurea from enterocytes, leading to increased serum levels and hypoglycemia.

Spironolactone increases the plasma concentration of digoxin by inhibiting tubular secretion, resulting in decreased renal clearance.
Hypokalemia, associated with thiazides and loop diuretics, increases the toxicity of digoxin.

Sildenafil should not be used with nitrates due to increased risk of hypotension.

The combination of aminoglycosides (amikacin, gentamycin) and furosemide reduces auditory nerve activity, impairing hearing.

Omega-3 fatty acids, ciprofloxacin, and metronidazole increase the anticoagulant effect of warfarin.
Vitamin K-rich food reduces the anticoagulant effect of warfarin.

Fluconazole, an antifungal agent, inhibits CYP450 3A4, increasing the plasma concentrations of statins, which can lead to musculoskeletal toxicity.

Calcium-rich food reduces the absorption of certain antibiotics (e.g., tetracyclines).
Antacids reduce the absorption of certain antibiotics.
Vitamin B6 increases the peripheral metabolism of levodopa, reducing its availability to the CNS.

Do not mix antibiotics with other injectable medications, especially gentamicin, due to physical and chemical incompatibility.
Do not give ceftriaxone with calcium IV solution, as it can cause precipitation of calcium in vital organs.
Do not give two NSAIDs together to children, as it can cause renal impairment.
Do not give multivitamins without lab analysis, as it can cause various adverse effects.
Do not give laxatives containing anthraquinone to pregnant women, as it can cause abortion.
Do not give antifungal medications like griseofulvin to pregnant women, as it can cause teratogenicity.
Do not give hypotensive medications to pregnant women, as it can cause maternal hypotension and abortion.
Do not give non-selective beta blockers to patients with bronchial asthma, diabetes, or angina.
Do not give isotretinoin to patients with liver or renal dysfunction, excessive hyperlipidemia, or those who are pregnant or breastfeeding.