POSTINOR®-1
Levonorgestrel 1.5 mg tablets
Presentation
Each round white tablet contains 1.5 milligrams of levonorgestrel.
Uses
Actions
The precise mode of action of Postinor-1 is not known. Emergency hormonal contraception is thought to work mainly by preventing ovulation and fertilisation by altering tubal transport of sperm and/or ova. It may also cause endometrial changes that discourage implantation.
Efficacy
It has been estimated that Postinor-1 prevents 85% of expected pregnancies. Efficacy appears to decline with time after intercourse (95% within 24 hours, 85% if used between 24 and 48 hours and/or 58% if used between 48 and 72 hours). Efficacy after 72 hours is unknown.
Indications
Postinor-1 is an oral emergency contraceptive indicated for use within 72 hours of unprotected intercourse. It should be used only as an emergency measure. Women who present for repeated courses of emergency contraception should be advised to consider long-term methods of contraception.
Dosage and Administration
One 1.5 milligram tablet to be taken as soon as possible (and not later than 72 hours) after unprotected intercourse.
The highest efficacy is achieved if the dose is started as early as possible.
If the patient vomits within two hours of taking the pills, she should return to her doctor or clinic where an additional pill may be given.
Postinor-1 can be used at any time during the menstrual cycle unless menstrual bleeding is overdue.
Children
Postinor-1 is not recommended in children. Limited data is available in young women of child-bearing potential aged 14 and over.
Contraindications
Postinor-1 should not be given to pregnant women. If menstrual bleeding is overdue, if the last menstrual period was abnormal in timing or character, or if pregnancy is suspected for any other reason, pregnancy should be excluded (by pregnancy testing or pelvic examination) before treatment is given.
If a woman has had unprotected intercourse more than 72 hours earlier in the same menstrual cycle, conception may have already occurred. Treatment with Postinor-1 following the second act of intercourse may therefore be ineffective in preventing pregnancy. While the consensus is that levonorgestrel is not teratogenic, no guarantee can be given that pregnancy will result in a normal baby.
Progestogen-only contraceptive pills (POPs) are used as a routine method of birth control over longer periods of time, and are contraindicated in some conditions. It is not known whether these same conditions apply to the Postinor-1 regimen consisting of the emergency use of two pills.
Traditionally, many of the contraindications to combined hormonal contraception have been applied to progestogen-only contraception. Since the contraindications largely apply to oestrogen, this is inappropriate. In their Medical Eligibility Criteria, The World Health Organisation advises that the only absolute contraindications to high dose progestogen-only contraception are unexplained vaginal bleeding, current breast cancer, pregnancy, or hypersensitivity to any of the ingredients of the preparation.
Warnings and Precautions
Conditions which are regarded as relative contraindications include severe hypertension (BP>180+/110+), diabetes mellitus with nephropathy, retinopathy, neuropathy or vascular disease, ischaemic heart disease, stroke, or a past history of breast cancer. Since exposure to levonorgestrel with Postinor-1 is brief, the risks of pregnancy in all women, including those with pre-existing medical conditions, are almost certainly greater than those associated with Postinor-1. In individual cases, the risk-benefit ratio should be assessed by the practitioner in discussion with the patient.
Postinor-1 is not as effective as conventional regular methods of contraception and is suitable only as an emergency measure. Women who present for repeated courses of emergency contraception should be advised to consider a long-term method of contraception.
Emergency contraception does not protect against sexually transmitted infections.
Further precautions for use
Exclude pregnancy if suspected clinically.
Breast or pelvic examinations are not routinely necessary. Perform such examinations only if indicated by the patient's history.
Blood pressure (BP) may be measured before prescribing Postinor-1. An elevated BP is not a contraindication to treatment but indicates the need for further investigation.
No routine laboratory testing is required.
Explain the importance of follow-up and the possibility of an early or late onset of the next menstrual period to the patient. Advise the practice of abstinence or careful use of a barrier method until the onset of the next period. Follow-up should be offered 3 weeks after administration of therapy to assess the effectiveness of the method, to discuss future management if a period has not occurred, and to counsel the patient about future contraception.
If pregnancy occurs after treatment with Postinor-1, the possibility of an ectopic pregnancy should be considered.
Vomiting, severe diarrhoea or other causes of malabsorption, such as Crohn's disease, might impair the efficacy of Postinor-1. Consideration should be given to the taking of more pills.
Effect on ability to drive and use machines
No effect is known.
Preclinical safety data
In acute toxicity studies performed in mice and rats levonorgestrel induced a decrease of body weight and dermatitis-like (non-irritative or non-allergic) changes on the skin.
In repeat dose toxicity studies performed in mice, rats and rabbits, there were no overt signs of toxicity and no target organs or functions were identified other than the reproductive system. These toxic effects observed on the reproductive system (stillbirth, fetotoxicity or changes in fertility index) can be regarded as an extreme manifestation of pharmacological effect of levonorgestrel due to the changes of hormone regulation.
Pregnancy and lactation
Use in Pregnancy
Postinor-1 should not be given to pregnant women. The effect of Postinor-1 on the foetus is unknown. Some investigators have suggested that sex hormones taken in the first trimester of pregnancy may slightly increase the risk of foetal malformations, but others have failed support these findings. The consensus opinion amongst teratologists is that known teratogens will not produce malformations before organogenesis starts, which is later than 72 hours after fertilisation.
Use in Lactation
There is no evidence that Postinor-1 taken only in an emergency situation diminishes the yield of breast milk. However, minute amounts of the active substance are excreted with the milk.
Adverse Effects
Nausea occurs in about 25% of women taking Postinor-1 and vomiting occurs in about 5% of women taking Postinor-1.
Bleeding patterns may be temporarily disturbed, but most women will have their next menstrual period at the expected time.
Some women may experience bleeding or spotting after taking Postinor-1 and some may experience early or delayed onset of menses. If the next menstrual period is more than 7 days overdue pregnancy should be excluded.
Other side effects include breast tenderness, headache, dizziness and fatigue.
Interactions
Some drugs accelerate the metabolism of oral contraceptives taken concurrently. Drugs suspected of having the capacity to reduce the efficacy of oral contraceptives include:
- barbiturates
- primidone
- phenytoin
- carbamazepine
- phenylbutazone
- rifampicin
- ritonavir
- ampicillin
- griseofulvin
The requirement for oral anti-diabetics and insulin can change as a result of an effect on glucose tolerance.
Overdosage
Serious ill effects have not been reported following acute ingestion of large doses of oral contraceptives. Overdose may cause nausea, and withdrawal bleeding may occur. There are no specific antidotes and treatment should be symptomatic.
Pharmaceutical Precautions
Shelf-life: 5 years.
Special precautions for storage: Store below 25°C
Package Quantities
Postinor-1 contains one blister aluminium/PVC blister sheet containing one tablet.
Further Information
List of excipients
- potato starch
- maize starch
- colloidal silica anhydrous
- gelatin
- magnesium stearate
- talc
- lactose monohydrate
Instructions for use/handling
Keep out of reach of children.
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