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Ovral (Norgestrel) - Drug Interactions, Contraindications, Overdosage, etc

 
 



9. DRUG INTERACTIONS

Changes in contraceptive effectiveness associated with coadministration of other products:

Contraceptive effectiveness may be reduced when hormonal contraceptives are coadministered with antibiotics, anticonvulsants, and other drugs that increase the metabolism of contraceptive steroids. This could result in unintended pregnancy or breakthrough bleeding. Examples include rifampin, rifabutin, barbiturates, primidone, phenylbutazone, phenytoin, dexamethasone, carbamazepine, felbamate, oxcarbazepine, topiramate, griseofulvin, and modafinil.

Several cases of contraceptive failure and breakthrough bleeding have been reported in the literature with concomitant administration of antibiotics such as ampicillin and other penicillins, and tetracyclines, possibly due to a decrease of enterohepatic recirculation of estrogens. However, clinical pharmacology studies investigating drug interactions between combined oral contraceptives and these antibiotics have reported inconsistent results. Enterohepatic recirculation of estrogens may also be decreased by substances that reduce gut transit time.

Several of the anti-HIV protease inhibitors have been studied with coadministration of oral combination hormonal contraceptives; significant changes (increase and decrease) in the plasma levels of the estrogen and progestin have been noted in some cases. The safety and efficacy of oral contraceptive products may be affected with coadministration of anti-HIV protease inhibitors. Health-care professionals should refer to the label of the individual anti-HIV protease inhibitors for further drug-drug interaction information.

Herbal products containing St. John's Wort (Hypericum perforatum) may induce hepatic enzymes (cytochrome P 450) and p-glycoprotein transporter and may reduce the effectiveness of contraceptive steroids. This may also result in breakthrough bleeding.

During concomitant use of ethinyl estradiol containing products and substances that may lead to decreased plasma steroid hormone concentrations, it is recommended that a nonhormonal back-up method of birth control be used in addition to the regular intake of Ovral. If the use of a substance which leads to decreased ethinyl estradiol plasma concentrations is required for a prolonged period of time, combination oral contraceptives should not be considered the primary contraceptive.

After discontinuation of substances that may lead to decreased ethinyl estradiol plasma concentrations, use of a nonhormonal back-up method of birth control is recommended for 7 days. Longer use of a back-up method is advisable after discontinuation of substances that have led to induction of hepatic microsomal enzymes, resulting in decreased ethinyl estradiol concentrations. It may take several weeks until enzyme induction has completely subsided, depending on dosage, duration of use, and rate of elimination of the inducing substance.

Increase in plasma levels associated with coadministered drugs:

Coadministration of atorvastatin and certain oral contraceptives containing ethinyl estradiol increase AUC values for ethinyl estradiol by approximately 20%. The mechanism of this interaction is unknown. Ascorbic acid and acetaminophen increase the bioavailability of ethinyl estradiol since these drugs act as competitive inhibitors for sulfation of ethinyl estradiol in the gastrointestinal wall, a known pathway of elimination for ethinyl estradiol. CYP 3A4 inhibitors such as indinavir, itraconazole, ketoconazole, fluconazole, and troleandomycin may increase plasma hormone levels. Troleandomycin may also increase the risk of intrahepatic cholestasis during coadministration with combination oral contraceptives.

Changes in plasma levels of coadministered drugs:

Combination hormonal contraceptives containing some synthetic estrogens (eg, ethinyl estradiol) may inhibit the metabolism of other compounds. Increased plasma concentrations of cyclosporin, prednisolone and other corticosteroids, and theophylline have been reported with concomitant administration of oral contraceptives. Decreased plasma concentrations of acetaminophen and increased clearance of temazepam, salicylic acid, morphine, and clofibric acid, due to induction of conjugation (particularly glucuronidation), have been noted when these drugs were administered with oral contraceptives.

The prescribing information of concomitant medications should be consulted to identify potential interactions.

OVERDOSAGE

Symptoms of oral contraceptive overdosage in adults and children may include nausea, vomiting, and drowsiness/fatigue; withdrawal bleeding may occur in females. There is no specific antidote and further treatment of overdose, if necessary, is directed to the symptoms.

NONCONTRACEPTIVE HEALTH BENEFITS

The following noncontraceptive health benefits related to the use of oral contraceptives are supported by epidemiological studies which largely utilized oral-contraceptive formulations containing doses exceeding 0.035 mg of ethinyl estradiol or 0.05 mg of mestranol.

Effects on menses:

Increased menstrual cycle regularity

Decreased blood loss and decreased incidence of iron-deficiency anemia

Decreased incidence of dysmenorrhea

Effects related to inhibition of ovulation:

Decreased incidence of functional ovarian cysts

Decreased incidence of ectopic pregnancies

Effects from long-term use:

Decreased incidence of fibroadenomas and fibrocystic disease of the breast

Decreased incidence of acute pelvic inflammatory disease

Decreased incidence of endometrial cancer

Decreased incidence of ovarian cancer

CONTRAINDICATIONS

Combination oral contraceptives should not be used in women with any of the following conditions:

Thrombophlebitis or thromboembolic disorders

A past history of deep-vein thrombophlebitis or thromboembolic disorders

Cerebral-vascular or coronary-artery disease (current or history)

Thrombogenic valvulopathies

Thrombogenic rhythm disorders

Major surgery with prolonged immobilization

Diabetes with vascular involvement

Headaches with focal neurological symptoms

Uncontrolled hypertension

Known or suspected carcinoma of the breast or personal history of breast cancer

Carcinoma of the endometrium or other known or suspected estrogen-dependent neoplasia

Undiagnosed abnormal genital bleeding

Cholestatic jaundice of pregnancy or jaundice with prior pill use

Hepatic adenomas or carcinomas, or active liver disease, as long as liver function has not returned to normal

Known or suspected pregnancy

Hypersensitivity to any of the components of Ovral-28

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