Contraceptive failure

Lack of efficacy in critical situations may also be reported, such as failure of antibiotics to treat life-threatening infections, or vaccine or contraceptive failures. 

As described earlier, many of the side effects of COCs may be minimized by adjusting the amount of hormones within the pill. However, while low- and ultra-low-dose COCs may cause fewer side effects, it is important to note that in the event that doses are missed, such COCs may be more likely to result in contraceptive failure. 

Adolescents, underweight women (<110 lb [50 kg]), women older than 35 years, and those who are perimenopausal may have fewer side effects with OCs containing 20 to 25 meg of EE. However, these low-estrogen OCs are associated with more breakthrough bleeding and an increased risk of contraceptive failure if doses are missed. 

Women weighing more than 160 lb (72.7 kg) may have higher contraceptive failure rates with low-dose OCs and may benefit from pills containing 35 to 50 meg of EE. 

Emergency contraception (Plan B and Proven only) For prevention of pregnancy following unprotected intercourse or a known or suspected contraceptive failure. To obtain efficacy, take the first dose as soon as possible within 72 hours of intercourse. The second dose must be taken 12 hours later. Emergency contraceptive pills are not indicated for ongoing pregnancy protection and should not be used as a woman s routine form of contraception. 

Ectopic as well as intrauterine pregnancy may occur in contraceptive failures. Lactation Hormonal contraceptives may interfere with lactation, decreasing both the quantity and the quality of breast milk. A small amount of OC steroids is excreted in breast milk. A few adverse effects on the nursing infant have been reported, including jaundice and breast enlargement. 

Hormonal Breakthrough bleeding and contraceptive failures reported... 

Cytochrome P450 inducer (oral contraceptive failure) Autoinduction Rare blood cell dyscrasias aplastic anemia, agranulocytosis Hepatotoxicity Rash risk, including Stevens-Johnson syndrome Risk for SIADH Teratogenicity risk neural tube defects, craniofacial defects... 

Carbamazepine induces hepatic cytochrome P450 (CYP) enzymes, which may reduce levels of other medications. Through the mechanism of hepatic enzyme induction, carbamazepine therapy can lead to oral contraceptive failure therefore, women should be advised to consider alternative forms of birth control while taking carbamazepine. Similarly, use of medications or substances that inhibit CYP 3A3/4 (discussed in Chapter 1) may result in significant increases in plasma carbamazepine levels. 

The postcoital (morning after) contraception is recommended within 48 hours after an unprotected intercourse, rape or contraceptive failure. 

Weisberg E Interactions between oral contraceptives and antifungals/antibacterials. Is contraceptive failure the result Clin Pharmacokinet 1999 36 309. [PMID 10384856]... 

Anonymous. Oral contraceptives. Ectopic pregnancy following emergency oral contraceptive failure. WHO Pharmaceuticals Newslett 2002 4 10. 

In Burkina Faso, experience in 1660 women over 4 years has been critically reviewed (18). There were 247 withdrawals before the fourth year, for various reasons, including cycle disorders (60 withdrawals), unspecified medical reasons (n = 53), personal objections (n = 47), weight gain (n = 14), and contraceptive failure (n = 2). Menstrual disorders, including amenorrhea, spotting, and hypermenorrhea, occurred in 51% of the cases. The... 

Moreno, L., and N. Goldman. 1991. Contraceptive failure rates in developing countries Evidence from the demographic and health surveys. Int Fam Plan Perspect 17 44. 

Jones, E.F., and J.D. Forrest. 1992. Contraceptive failure rates based on the 1988 NSFG. Fam Plan Perspect 24 12. 

Meanwhile, the currently marketed CYP3A4 inducers can profoundly affect the pharmacokinetics of coadministered CYP3A4 substrates, e.g., rifampin on midazolam (139) or triazolam (140). Clearly, the most frequent outcome is a loss of efficacy, which is perhaps less serious than inhibition interactions, although the consequences of coadministering rifampin with the oral contraceptive pill can lead to contraceptive failure (141-143). 

APREPITANT 0ESTR0GENS 1 oestrogen levels with risk of contraceptive failure Uncertain Clinical significance uncertain. It would seem wise to advise patients to use an alternative form of contraception during and for 1 month after stopping co-administration with these drugs... 

NEVIRAPINE PROGESTOGENS- NORETHISTERONE 1 efficacy of contraceptives, with risk of contraceptive failure Uncertain Avoid co-administration recommend alternative non-hormonal contraceptives - barrier methods are necessary to prevent transmission of infection... 

PROTEASE INHIBITORS PROGESTOGENS -NORETHISTERONE t adverse effects with amprenavir and atazanavir. Possibly 1 efficacy and risk of contraceptive failure with nelfinavir and ritonavir (with or without lopinavir) Uncertain Advise patients to use additional contraception for the period of intake and for 1 month after stopping coadministration with these drugs. Barrier methods are necessary to prevent transmission of infection from patients with HIV. Watch for early features of toxicity of amprenavir and atazanavir, and adjust the dose accordingly... 

St John s wort 2. Red clover 3. Saw palmetto 1. Oral contraceptives Failure of contraception. Theoretically, saw palmetto could interfere with oral contraception and hormone replacement therapy St John s wort preparations induce metabolizing CYP3A4 enzymes and glycoprotein drug transporters of these medications Avoid concomitant use. Use an alternative contraceptive methods (barrier methods) if the herb is introduced... 

As no other cause for contraceptive failure could be identified, the authors concluded that the St. John s wort had been responsible. 

It therefore appears that there is no threat of contraceptive failure because of concomitant fluconazole administration. 

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