NSAIDs Phenobarbital

Drugs that are the most common cause of TEN are allopurinol, ampicillin, amoxicillin, carbamazepine, NSAIDs, phenobarbital, pentamidine, phenytoin (diphenylhydantoin), pyrazolones, and sulfonamides. 

NSAIDs or phenobarbital, their antihypertensive effects may be decreased. 

Drugs that affect NSAIDs include the following Bisphosphonates, cholestyramine, cimetidine, colestipol, cyclosporine, diflunisal, DMSO, fluconazole, ketoconazole, phenobarbital, phenylbutazone, probenecid, rifampin, ritonavir, salicylates, sucralfate. 

Drugs that may affect donepezil are CYP450 3A4 and 2D6 inhibitors (eg, ketoconazole, quinidine) and CYP450 3A4 and 2D6 inducers (eg, carbamazepine, dexamethasone, phenobarbital, phenytoin, rifampin). Drugs that may be affected by donepezil include anticholinergics, cholinometics/cholinesterase inhibitors, NSAIDs. 

Uses Edema, HTN, CHF, h atic cirrhosis Action Loop diuretic -1- reabsorption of Na Cr in ascending loop of Henle distal tubule Dose 5-20 mg/d PO or IV 200 mg/d max Caution [B, ] Contra Sulfonylurea sensitivity Disp Tabs, inj SE Orthostatic -1- BP, HA, dizziness, photosens, electrolyte imbalance, blurred vision, renal impair Notes 20 mg torsemide = 40 mg furosemide Interactions t Risk of ototox W/ aminoglycosides, cisplatin t effects W/ thiazides t effects OF anticoagulants, antih5rpCTtensives, Li, salicylates X effects IT/barbiturates, carbamaz ine, cholestyramine, NSAIDs, phenytoin, phenobarbital, probenecid, dandehon EMS t Effects of anticoagulants monitor for S/Sxs tinnitus, monitor ECG for hypokalemia (flattened T waves) OD May cause HA, hypotension, hypovolemia, and hypokalemia give IV fluids symptomatic and supportive... 

The probable reason is that the phenobarbital increases the metabolism of these NSAIDs by the liver, thereby hastening their clearance. Phenazone is metabolised by mixed function oxidase enzymes in the liver, for which reason it is extensively used as a model drug for studying whether other drugs induce or inhibit liver enzymes. In one study phenobarbital caused about a 40% reduction thereby demonstrating that the liver enzymes were being stimulated to metabolise the phenazone more rapidly. The clinical importance of these interactions is uncertain (probably small) but be alert for any evidence of reduced NSAID effects if phenobarbital is added. 

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