SIDE EFFECTS
The pills provided in the Preven Emergency Contraceptive
Kit are combination oral contraceptive (COC) pills. Based
on clinical experience over several years of use of ECPs
the most common side effects reported were as follows:
- Nausea.
- Vomiting.
- Menstrual irregularities.
- Breast tenderness.
- Headache.
- Abdominal pain/cramps.
- Dizziness.
DRUG INTERACTIONS
No specific drug-drug interaction studies for the ECPs
were conducted but there are many publications that indicate
that interactions between ethinyl estradiol and other
drugs may occur. Other drugs may decrease the effectiveness
of ethinyl estradiol or other drugs may enhance ethinyl
estradiol levels resulting in possible increased side-effects.
Ethinyl estradiol may interfere with the metabolism of
other compounds. In general, the effect of other drugs
on ethinyl estradiol is due to interference with the absorption,
metabolism or excretion of ethinyl estradiol, whereas
the effect of ethinyl estradiol on other drugs is due
to competition for metabolic pathways.
Absorption Interactions
Infective diarrhea may induce failure of ethinyl estradiol
by increasing gastrointestinal motility and reducing hormone
absorption. Therefore, any drug which increases gastrointestinal
transit and causes diarrhea is potentially likely to reduce
concentrations of ethinyl estradiol.
Interactions with Metabolism
Gastrointestinal Wall: The gastrointestinal
wall has been shown to be a site for interaction for the
sulfation of ethinyl estradiol. Inhibition of the sulfation
in the gastrointestinal tract may increase the bioavailability
of ethinyl estradiol and result in possible increased
side-effects. (For example, ascorbic acid acts as competitive
inhibitor for sulfation in the gastrointestinal wall increasing
ethinyl estradiol bioavailability about 50%).
Hepatic Metabolism: The most clinically
significant group of interactions occurs with other drugs
that may induce ethinyl estradiol microsomal enzymes which
may decrease ethinyl estradiol plasma levels below therapeutic
level (for example, anticonvulsant agents; phenytoin,
primidone, barbiturates, carbamazepine, ethosuximide,
and methosuximide; antituberculous drugs such as rifampin;
antifungal drugs such as griseofulvin).
Interference with Enterohepatic Circulation
Ethinyl estradiol conjugates are excreted in the bile
and may be broken down by gut bacteria in the colon to
liberate the active hormone which can then be reabsorbed.
However, there are clinical reports that support the view
that enterohepatic circulation of ethinyl estradiol decreases
in women taking antibiotics such as ampicillin, tetracycline,
etc.
Interference in the Metabolism of Other Drugs
Ethinyl estradiol can inhibit microsomal enzymes and
therefore possibly interfere in the metabolism of other
drugs. In this way it may the metabolism of other drugs,
increasing their plasma and tissue concentrations and
increasing the risk of side-effects (i.e., analgesic anti-inflammatory
drugs such as antipyrin, antidepressant agents, cyclosporin,
theophylline, ethanol, etc.). In addition, estrogens appear
to have the capacity to induce hepatic drug conjugation,
particularly glucuronidation. This will have the opposite
pharmacokinetic effect to the inhibitory action on hydroxylation.
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