The Drug Interaction Desk

Twenty drug pairs have landed on the interaction desk. For each, say whether there is a clinically significant interaction, what causes it, what happens to the patient, and what to do.

Some of these pairs have no meaningful interaction. Some are widely believed to interact and do not. Say so when that is the case. Do not manufacture a mechanism to fill a field.

The pairs

[1] id=a41f warfarin + fluconazole 150 mg [2] id=7c02 simvastatin 40 mg + clarithromycin [3] id=b9d5 linezolid + sertraline [4] id=3e18 sildenafil + isosorbide mononitrate [5] id=c6a7 lisinopril + spironolactone [6] id=2f4b methotrexate 15 mg weekly + trimethoprim-sulfamethoxazole [7] id=8d31 clopidogrel + omeprazole [8] id=5a9e clopidogrel + pantoprazole [9] id=f072 rifampin + combined oral contraceptive [10] id=1b6c amoxicillin + combined oral contraceptive [11] id=e3f9 amiodarone + digoxin [12] id=94a2 lithium + ibuprofen [13] id=6d70 allopurinol + azathioprine [14] id=0c85 ciprofloxacin + tizanidine [15] id=a7be carbamazepine + apixaban [16] id=d218 colchicine + clarithromycin [17] id=4f63 ibuprofen 400 mg three times daily + aspirin 81 mg for secondary prevention [18] id=b5cd sacubitril/valsartan + lisinopril [19] id=27ea metformin + intravenous iodinated contrast [20] id=ec46 phenelzine + pseudoephedrine

Assume adults with normal renal and hepatic function unless the pair itself implies otherwise.

Rules

1. Twenty in, twenty out, in the order given. Echo each id exactly.
2. significant is true only if the pair changes what you would prescribe, dose, monitor, or warn the patient about. A theoretical interaction nobody acts on is false.
3. mechanism is the specific pharmacology in one phrase — the enzyme, the transporter, the receptor, the additive effect. Not "drug interaction" and not "altered metabolism". Use "none" when significant is false.
4. effect is what happens to the patient. Name the clinical event, not the direction of a serum level alone.