Oral contraceptives anticonvulsants

Folic acid deficiency can be caused by drugs that interfere with folate absorption or metabolism. Phenytoin, some other anticonvulsants, oral contraceptives, and isoniazid can cause folic acid deficiency by interfering with folic acid absorption. Other drugs such as methotrexate and, to a lesser extent, trimethoprim and pyrimethamine, inhibit dihydrofolate reductase and may result in a deficiency of folate cofactors and ultimately in megaloblastic anemia. 

Antibiotics, antiinflammatories, opiate analgesics Antibiotics, anticonvulsants, oral contraceptives Sulfonamides, gold, isoniazid, streptomycin quinicrine antimalarials (see Table 5)... 

The effects of the progestins are decreased when administered with anticonvulsants, barbiturates, or rifampin. Administration of the penicillins or tetracyclines with the oral contraceptives decreases the effects of the oral contraceptives. 

Drugs that may affect nelfinavir include anticonvulsants, azithromycin, azole antifungals, efavirenz, delavirdine, HMG-CoA reductase inhibitors, indinavir, interleukins, nevirapine, rifabutin, rifampin, ritonavir, saquinavir, St. John s wort. Drugs that may be affected by nelfinavir include amiodarone, antiarrhythmics (amiodarone, quinidine), azithromycin, benzodiazepines, efavirenz, ergot alkaloids, delavirdine, didanosine, fentanyl, indinavir, lamivudine methadone, nonsedating antihistamines, oral contraceptives, phenytoin, pimozide, quinidine, rifabutin, saquinavir, sildenafil, sirolimus, tacrolimus, zidovudine. 

Drugs that might affect amprenavir include abacavir, aldesleukin, antacids, anticonvulsants, azole antifungals, clarithromycin, cyclosporine, dexamethasone, buffered didanosine, disulfiram, ethanol, indinavir, methadone, metronidazole, nelfinavir, nonnucleoside reverse transcriptase inhibitors, oral contraceptives, rifamycins, ritonavir, saquinavir, St. John s wort, tacrolimus, and zidovudine. 

Drugs that might be affected by amprenavir include antiarrhythmics, anticonvulsants, azole antifungals, benzodiazepines, calcium channel blockers, cisapride, clarithromycin, cyclosporine, ergot alkaloids, fentanyl, HMG-CoA reductase inhibitors, indinavir, methadone, nelfinavir, oral contraceptives, pimozide, rifabutin, ritonavir, saquinavir, sildenafil, tacrolimus, trazodone, tricyclic antidepressants, warfarin, and zidovudine. 

Drugs that may affect cyclosporine include allopurinol, amiodarone, androgens (eg, danazol, methyltestosterone), anticonvulsants (eg, carbamazepine, phenobarbital, phenytoin), azole antifungals (eg, fluconazole, ketoconazole), beta-blockers, bosentan, bromocriptine, calcium channel blockers, colchicine, oral contraceptives, corticosteroids, fluoroquinolones (eg, ciprofloxacin), foscarnet, HMG-CoA reductase inhibitors, imipenem-cilastatin, macrolide antibiotics, methotrexate, metoclopramide, nafcillin, nefazodone, orlistat, potassium-sparing diuretics, probucol, rifamycins (rifampin, rifabutin), serotonin reuptake inhibitors (SSRIs eg, fluoxetine, sertraline),... 

Sustained-release formulations can produce stable serum concentrations with once or twice daily dosage. Therapeutic effects occur at blood levels > 5 mg/1, and side effects increase considerably at levels > 15 mg/1. Smoking, alcohol, anticonvulsants, and rifampicin induce the drug-metabolizing enzyme system in liver and reduce the half-life of theophylline. On the other hand, heart and liver failure, sustained fever, old age and drugs such as cimeti-dine, ciprofloxacin, and oral contraceptives reduce theophylline clearance and thereby increase serum concentrations. 

Gabapentin does not bind to plasma proteins, is not appreciably metabolized, nor induces hepatic enzyme activity (AHFS, 2000) Consequently, it does not appear to alter the pharmacokinetics of commonly used anticonvulsant drugs or oral contraceptives (Ketter et al.,... 

The newer anticonvulsants have not been studied as intensively as the older drugs as regards the possibility of interference with the effects of oral contraceptives. The available data suggest that women taking oral contraceptives can also take gabapentin, lamotrigine, tiagabine, and... 

Wilbur K, Ensom MH. Pharmacokinetic drug interactions between oral contraceptives and second-generation anticonvulsants. Clin Pharmacokinet 2000 38(4) 355-65. 

Use of St. John s Wort is complicated by the lack of standardisation of the ingredients. Those who wish to take St. John s Wort should be made aware that it may cause dry mouth, dizziness, sedation, gastrointestinal disturbance and confusion. Importantly also, it induces hepatic P450 errzymes (CYP 1A2 and CYP 3A4) with the result that the plasma concentration and therapeutic efficacy of warfarin, oral contraceptives, some anticonvulsants, antipsychotics and HTV protease/reverse transcriptase inhibitors are reduced. Concomitant use of tr5 to-phan and St John s Wort may cause serotonergic effects including nausea and agitation. 

Certain drugs such as anticonvulsants and oral contraceptives can impair the absorption of folate. Anticonvulsants also increase the rate of folate metabolism. 

Back DJ, Grimmer SF, Orme ML, Proudlove C, Mann RD, Breckemidge AM. Evaluation of Committee on Safety of Medicines yellow card reports on oral contraceptive-drug interactions with anticonvulsants and antibiotics. Br J Qin Pharmacol 1988 25(5) 527-32. 

Folic acid is a nutritional supplement frequently used during periods of deficiency. Folic acid needs increase during chronic diseases, such as malabsorption liver disease, alcoholism, and anticonvulsant or oral contraceptive use. Folic acid supplementation during pregnancy is strongly recommended to prevent neural tube defects to the unborn child. The active form of folic acid, folinic acid, is used in the management of certain medical diseases (e.g., patients taking methotrexate, and 5-fluorouracil). 

The most common drugs responsible for acneform eruptions are ACTH, androgenic hormones, anticonvulsants (hydantoin derivatives, phenobarbital, trimethadione), corticosteroids, danazol, disulfiram, halogens (bromides, chlorides, iodides), lithium, oral contraceptives, tuberculostatics (ethionamide, isoniazid, rifampin), vitamins B2, B6, and B12. 

Drugs corticosteroids isotretmoin (Accutane), thiazides, anticonvulsants, j5 blockers, anabolic steroids, certain oral contraceptives Alcohol Obesity... 

I Drug-Drug Interactions. Carbamazepine induces the hepatic cytochrome P450 isoenzymes (1A2, 3A4, 2C9/10, and 2D6), which increases the metabolism of many medications, such as anticonvulsants (i.e., lamotrigine, topiramate, and valproate), antidepressants (i.e., tricyclics and bupropion), antipsychotics (i.e., clozapine, haloperi-dol, fluphenazine, olanzapine, and thiothixene), benzodiazepines, oral contraceptives, and protease inhibitors. " Women who receive carbamazepine require higher dosages of oral contraceptives or alternative contraceptive methods." ... 

Sedatives or anticonvulsants (e.g., carbamazepine, oxcarbazepine, phenobarbital, and pheny-toin, but not valproate) that induce CYPs (see Chapter S) can enhance the metabolism of antipsychotic and many other agents (including anticoagulants and oral contraceptives), sometimes with significant clinical consequences. Conversely, selective serotonin (5-HT) reuptake inhibitors including fluvoxamine, fluoxetine, paroxetine, venlafaxine, sertraline, and nefazodone (see Chapter 17) compete for these enzymes and can elevate circulating levels of neuroleptics. 

FOLATE DEFICIENCY Folate deficiency is a common complication of diseases of the small intestine, which interfere with the absorption of dietary folate and the recirculation of folate through the enterohepatic cycle. In acute or chronic alcohohsm, daily intake of dietary folate may be severely restricted, and the enterohepatic cycle of the vitamin may be impaired by toxic effects of alcohol on hepatic parenchymal cells this is the most common cause of folate-deficient megaloblastic erythropoiesis. However, it also is the most amenable to therapy, inasmuch as the reinstitution of a normal diet is sufficient to overcome the effect of alcohol. Disease states characterized by a high rate of cell turnover, such as hemolytic anemias, also may be complicated by folate deficiency. Additionally, drugs that inhibit dihydrofolate reductase (e.g., methotrexate and trimethoprim) or that interfere with the absorption and storage of folate in tissues (e.g., certain anticonvulsants and oral contraceptives) can lower the concentration of folate in plasma and may cause a megaloblastic anemia. 

Anticonvulsive drugs in general have additive depressive effects when used with other depressant drugs, cause a precipitation of seizures upon abrupt withdrawal, and decrease the efficiency of oral contraceptives. 

Drug Interactions Contraceptive effects are decreased when "the pill" is taken with ANTIDIOTICS (ampicillin, isoniazid, neomycin, pen V, rifampin, sulfonamides, tetracycline) or CNS AGENTS (barbiturates, benzodiazepines, phenytoin). Contraceptives increase the effects of corticosteroids and worsen side effects of tricyclic antidepressants. Oral contraceptives decrease the effectiveness of oral anticoagulants, anticonvulsants, and oral hypoglycemic agents. 

P9. Pritchard, J. A., Scott, D. E., and Whalley, P. J., Maternal folate deficiency and pregnancy wastage. IV. Effects of folic acid supplements, anticonvulsants, and oral contraceptives. Amer. J. Obstet. Gynecol. 109, 341-346 (1971). 

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