Phenobarbital Cortisol

P-gp (ABCB1) Verapamil, digoxin, mitoxantrone, vinblastine, doxorubicin, losartan, talinolol, cortisol, dexamethasone, colchicine, loperamide, domperidone, indinavir, erythromycin, tetracycline, itraconazole, cyclosporine, methotrexate, amitryptyline, phenobarbital, morphine, cimetidine, and others... 

Primary adrenal insufficiency (Addison s disease) most often involves the destruction of all regions of the adrenal cortex. There are deficiencies of cortisol, aldosterone, and the various androgens. Medications that inhibit cortisol synthesis (e.g., ketoconazole) or accelerate cortisol metabolism (e.g., phenytoin, rifampin, phenobarbital) can also cause primary adrenal insufficiency. 

Phenobarbital and Barbiturates, chloramphenicol, chlorpromazine, cortisol, coumarin anticoagulants,... 

Neither phenytoin, valproate, carbamazepine, nor phenobarbital altered the circadian ACTH/cortisol rhythm in epileptic patients (95). In some studies, phenytoin and... 

Phenobarbital and other barbiturates1 Barbiturates, chloramphenicol, chlorpromazine, cortisol, coumarin anticoagulants, desmethylimipramine, digitoxin, doxorubicin, estradiol, phenylbutazone, phenytoin, quinine, testosterone... 

Ammonia Amylase pancreatic ALP total Cortisol Phenobarbital... 

Elepatic mixed-function oxidases are induced by many drugs, including phenytoin, phenobarbital, mitotane, aminoglutethunide, and rifampin. In addition, bp-hydroxylase and other drug-metabohzing pathways that metabolize cortisol and otlier steroids are increased by a... 

Interpretation In normal subjects, serum cortisol concentration is suppressed to 2 pg/dL or less after administration of 1 mg of dexamethasone. Most patients with Cushing s syndrome do not show adequate suppression, and 0800 hours cortisol concentrations are usually >10pg/dL. Serum cortisol >2pg/dL may also be seen in cases of stress, obesity, infection, acute or chronic illness, alcohol abuse, severe depression, oral contraceptive use, pregnancy, estrogen therapy, failure to take the dexamethasone, or treatment with phenytoin or phenobarbital (enhancement of dexamethasone metabolism). 

Interpretation Normal subjects have suppressed serum and urinary free cortisol concentrations on day 4 to <50% of baseline values serum cortisol at 2000 hours on day 1 should be one third of the value at 0800 hours. Patients with Cushing s syndrome usually do not show diurnal rhythmicity and do not show suppression with low-dose dexamethasone. Those patients taking phenytoin or phenobarbital, or both, metabolize dexamethasone more rapidly than do normal subjects and may not show suppression. 

B24. Burstein, S., Determination of initial rates of cortisol 2a-and 6a-hydroxylation by hepatic microsomal preparations in guinea pigs Effect of phenobarbital in two genetic types. Endocrinology 82, 547-554 (1968). 

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... 

Six CMIA mono-immunoassays were developed (cf Table 8.1). The first of these were in the area of clinical biology, with CMIA assays of antiepileptic medications such as carbamazepine [45], phenobarbital [71], diphenylhydantoin [26, 32], and a steroid hormone, cortisol [70]. More recently they have been extended into the environmental area, with assays of pesticides atrazine [44] and chlortoluron [39]. All these assays used polyclonal antibodies. For each of the analytes dilution curves and standard curves were obtained. The curves obtained for carbamazepine, representative of the results for all compounds, are shown in Fig. 8.8. 

In humans, administration of o,p -DDD [l,l-dichloro-2-(4-chlorophenyl)-2-(2-chlorophenyl) ethane], phenobarbital, diphenylhydantoin, or phenylbutazone causes a marked elevation in the urinary excretion of 6 )5-hydroxycortisol presumably by accelerating the metabolism of glucocorticoids. Accordingly, treatment of animals with phenobarbital stimulates the hydroxylation by hepatic microsomes of corticosterone, deoxycorticosterone, cortisone, and cortisol, whereas 3-methylcholanthrene has negligible effect on the hydroxylation of cortisone or cortisol. The physiological consequences of this induction, however, remain obscure. 

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