Recommendations for Contraceptive Use
		Oral Contraceptives as Emergency Contraceptive Pills

Recommendations	Rationale
a) Probably. While there is little direct information for drug interactions with ECPs, known drug interactions with combined oral contraceptives (COCs) should be presumed to apply to ECPs.	a) Anticonvulsants, especially hydantoins (e.g., phenytoin), barbiturates (e.g., primidone, phenobarbital), and carbamazepine (non-barbiturates) lead to increased metabolism, thus eliminating estrogen and progestin in the bile and decreasing the effectiveness of COCs (newly marketed anti-epileptics, including vigabatrin, lamotrigine, and valproic acid are not included). Anderson GD, Graves NM. Drug interactions with antiepileptic agents. CNS Drugs 1994;2(4):268-79. Webb A. How safe is the Yuzpe method of emergency contraception? Fertility Control Reviews 1995;4:2:16-18 Orme M, Back DJ. Oral contraceptive steroids - pharmacological issues of interest to the prescribing physician. Advances in Contraception 1991;7:325-31. Rifampin/rifampicin (anti-tuberculosis) and griseofulvin (anti-fungal) cause hepatic micro-enzyme induction, thus reducing blood levels of COCs; it is presumed the effectiveness of the ECP regimen is also reduced. Orme M, Back DJ. Oral contraceptive steroids - pharmacological issues of interest to the prescribing physician. Advances in Contraception 1991;7:325-31. Angle M, Huff P, Lea J. Interactions between oral contraceptives and therapeutic drugs. Outlook 1991;9(1):1-6.
b) Women taking liver enzyme-inducing drugs, mainly anticonvulsant treatments (phenytoin, phenobarbitol, and carbamazepine) and the antibiotic rifampicin, may have to take a higher dose than the recommended ECP regimen. However, an increased dose of ECPs may increase the severity or duration of side effects.	b) For women taking anticonvulsants and rifampicin who require emergency contraception (EC), some experts have recommended doubling the ECP dose. Guillebaud J. Contraception: your questions answered. New York: Churchill Livingstone, 1993:114-5. Program for Appropriate Technology in Health. Emergency contraception: a resource manual for providers. Seattle: PATH, 1997.
c) Since most anticonvulsants are associated with a risk of birth defects, prevention of unplanned pregnancy is particularly important.	c) Almost all anticonvulsants are teratogenic. Drug facts and comparisons. St. Louis: Facts and Comparisons, January 1997. Mattson RH, Rebar RW. Contraceptive methods for women with neurologic disorders. American Journal of Obstetrics and Gynecology 1993;168:2027-32.
d) It is unlikely that broad spectrum antibiotics significantly affect the action of COCs, including ECPs.	d) There is evidence that broad spectrum antibiotics do not decrease COC effectiveness, so in the absence of data for ECPs, the experts presume no clinically important effects on ECP use, either. Back DJ, Orme M. Drug interactions. In: Goldzieher JW, Fotherby K, editors. Pharmacology of the contraceptive steroids. New York: Raven Press, 1994:407-26. Friedman CI, Huneke AL, Kim MH, Powell J. The effect of ampicillin on oral contraceptive effectiveness. Obstetrics and Gynecology 1980;55:33-6. Grimmer SFM, Allen WL, Back DJ, Breckenridge AM, Orme M, Tjia J. Cotrimoxazole on oral contraceptive steroids in women. Contraception 1983;28:53-9. Joshi JV, Joshi UM, Sankolli GM, Krishna U, Mandlekar A, Chowdhury V, et al. A study of interaction of a low-dose combination oral contraceptive with ampicillin and metronidazole. Contraception 1980;22:643-52.

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