Drug interactions between Fiorinal and Necon 1/50
| Results for the following 2 drugs: |
|---|
| Fiorinal (aspirin/butalbital/caffeine) |
| Necon 1/50 (mestranol/norethindrone) |
Interactions between your selected drugs
norethindrone ↔ butalbital
Applies to:Necon 1/50 (mestranol/norethindrone) and Fiorinal (aspirin/butalbital/caffeine)
ADDITIONAL CONTRACEPTION RECOMMENDED: Coadministration with a barbiturate may reduce the efficacy of contraceptive hormones. There have been numerous case reports of menstrual abnormalities (e.g., breakthrough bleeding, amenorrhea, irregular menses) and unintended pregnancy occurring in women who received oral contraceptives with phenobarbital. In a study of four women treated chronically with a contraceptive pill containing 50 mcg of ethinyl estradiol, coadministration with phenobarbital (30 mg twice a day) was associated with breakthrough bleeding and a greater than 60% reduction in plasma ethinyl estradiol concentration in two of the women. The interaction stems from accelerated clearance of contraceptive hormones as well as decreased plasma concentrations of unbound (active) hormones due to induction of hepatic CYP450 enzymatic activity and enhancement of hormone-binding globulin capacity by phenobarbital. Since all barbiturates are believed to possess enzyme-inducing capabilities, the interaction should be expected with agents in the class other than phenobarbital.
MANAGEMENT: Women using hormonal contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant therapy with barbiturates. Alternative or additional methods of birth control should be used during and for at least one week after short-term and 4 weeks after long-term (greater than 4 weeks) barbiturate therapy. No precautions or recommendations are available for women using hormone-releasing intrauterine systems, but a significant interaction with these systems is thought to be unlikely due to their local action. Injectable progestin-only contraceptives are also thought to be unaffected by barbiturates.
mestranol ↔ butalbital
Applies to:Necon 1/50 (mestranol/norethindrone) and Fiorinal (aspirin/butalbital/caffeine)
ADDITIONAL CONTRACEPTION RECOMMENDED: Coadministration with a barbiturate may reduce the efficacy of contraceptive hormones. There have been numerous case reports of menstrual abnormalities (e.g., breakthrough bleeding, amenorrhea, irregular menses) and unintended pregnancy occurring in women who received oral contraceptives with phenobarbital. In a study of four women treated chronically with a contraceptive pill containing 50 mcg of ethinyl estradiol, coadministration with phenobarbital (30 mg twice a day) was associated with breakthrough bleeding and a greater than 60% reduction in plasma ethinyl estradiol concentration in two of the women. The interaction stems from accelerated clearance of contraceptive hormones as well as decreased plasma concentrations of unbound (active) hormones due to induction of hepatic CYP450 enzymatic activity and enhancement of hormone-binding globulin capacity by phenobarbital. Since all barbiturates are believed to possess enzyme-inducing capabilities, the interaction should be expected with agents in the class other than phenobarbital.
MANAGEMENT: Women using hormonal contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant therapy with barbiturates. Alternative or additional methods of birth control should be used during and for at least one week after short-term and 4 weeks after long-term (greater than 4 weeks) barbiturate therapy. No precautions or recommendations are available for women using hormone-releasing intrauterine systems, but a significant interaction with these systems is thought to be unlikely due to their local action. Injectable progestin-only contraceptives are also thought to be unaffected by barbiturates.
See also...
Drug Interaction Classification
The classifications below are a guideline only. The relevance of a particular drug interaction to a specific patient is difficult to determine using this tool alone given the large number of variables that may apply.
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
Do not stop taking any medications without consulting your healthcare provider.
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