Methylprednisolone Phenobarbital

Drugs that may affect tacrolimus include nephrotoxic agents (aminoglycosides, amphotericin B, cisplatin, cyclosporine), antifungals, bromocriptine, calcium channel blockers, cimetidine, clarithromycin, danazol, diltiazem, erythromycin, methylprednisolone, metoclopramide, carbamazepine, phenobarbital, phenytoin, rifamycins, cisapride, chloramphenicol, metronidazole, nefazodone, omeprazole, protease inhibitors, macrolide antibiotics, fosphenytoin, and St. John s wort. 

Simultaneous acebutolol, acetazolamide, acetophenetidin, adrenosterone, aldosterone, amitriptyline, androsten-3,17-dione, aspirin, carbamazepine, cephalothin, chlorothiazide, dehydrocorticosterone, deoxycorticosterone, deo cortisol, desipramine, dexamethasone, diazepam, equilenin, estradiol, estriol, estrone, fluorometholone, furosemide, hydrochlorothiazide, hydroxycorticosterone, hydroxyprogesterone, hydroxyprogesterone, imip-ramine, indomethacin, methylhydroxyprogesterone, methylprednisolone, nandrolone, nordiazepam, nortriptyline, pheniramine, phenobarbital, phenytoin, prednisolone, prednisone, primidone, probenecid, progesterone, quinine, spironolactone, testosterone, theophylline, triamcinolone, tripelennamine... 

Phenobarbital increased the clearance of methylprednisolone in asthmatic children by 209%. ... 

The interaction between the corticosteroids and phenobarbital is well documented, well established and of clinical importance. Concurrent use need not be avoided but the outcome should be monitored. Increase the corticosteroid dosage as necessary. The extent of the increase is variable. Dex-amethasone, hydrocortisone, " methylprednisolone, prednisone and prednisolone are all known to be affected. Prednisone and prednisolone appear to be less affected than methylprednisolone and may be preferred. Be alert for the same interaction with other corticosteroids and other barbiturates, which also are enzyme-inducers, although direct evidence seems to be lacking. The dexamethasone adrenal suppression test may be expected to be unreliable in those taking phenobarbital, just as it is with pheny-toin, another potent enzyme-inducer. See Corticosteroids + Phenytoin , p.1059. 

Stjernholm MR, Katz FH. Effects of dii enylhydantoi phenobarbital, and diazepam on the metabolism of methylprednisolone and its sodium succmatd.JClinEndocrinolMetcA (1975) 41, 887-93. 

Information is limited but the interaction appears to be established. Patients taking carbamazepine are likely to need increased doses of dexamethasone, methylprednisolone or prednisolone. Prednisolone is less affected than methylprednisolone and is probably preferred. The same interaction seems likely with other corticosteroids but more study is needed to confirm this. Note that hydrocortisone and prednisone are affected by another potent enzyme inducer, phenobarbital , (p.l052), and would therefore also be expected to interact with carbamazepine. 

Troleandomycin and, to a lesser extent, clarithromycin and erythromycin can reduce the clearance of methylprednisolone, thereby increasing both its therapeutic and adverse effects. A patient receiving long-term clarithromycin developed Cushing s syndrome after starting treatment with inhaled budesonide. There appears to be no pharmacokinetic interaction between erythromycin and inhaled ciclesonide. Similarly, prednisolone appears not to be affected by macrolides, except possibly in those also taking enzyme-inducers such as phenobarbital. Isolated case reports describe the development of acute mania and psychosis in two patients, apparently due to an interaction between prednisone and clarithromycin. 

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