Description and Composition of Microval
Tablets dosage Form
Levonorgestrel Intrauterine System
Indications and Uses of Microval
Emergency Contraception (Tablets)
Microval is used to prevent pregnancy after unprotected sex especially when one is not in her safe period or if one is few days to her ovulation. It should be used within 72 hours after unprotected sex for it to be effective.
Although, it can still be used even after 72 hours but not beyond 120 hours. It however works better if used early. It is estimated that Levonorgestrel will prevent 85% of expected pregnancies. 95% of expected pregnancies will be prevented if taken within the first 24 hours, declining to 58% if taken between 48 hours and 72 hours after unprotected intercourse.
Long-term contraception or nonemergency contraception (IUDs)
In addition to the above indication in emergency contraception, levonorgestrel is combined with other contraceptives in contraceptive formulations designed for regular use, for example with ethinyl estradiol. It is used in various hormone-releasing intrauterine devices for long-term contraception ranging for a duration of 3-5 years.
Hormone therapy and off-label uses
Levonorgestrel is prescribed in combination with estradiol as hormone therapy during menopause to manage vasomotor symptoms and to prevent osteoporosis. Off-label, levonorgestrel may be used to treat menorrhagia, endometrial hyperplasia, and endometriosis.
Dosage of Microval
Emergency Contraception (Tablets)
Long-term contraception or nonemergency contraception (IUDs)
One IUD is inserted into your uterus by your doctor and removed at the manufacturer’s specified time. Levonorgestrel intrauterine system lasts between 3 to 5 years depending on brand. The 52-mg levonorgestrel-releasing intrauterine system is inserted in the uterus and releases up to 20 mcg of levonorgestrel per day (mean 14 mcg/day). The quantity of Levonorgestrel released per day progressively reduces over the years.
How Microval works
Mechanism of action of Microval
Microval works in three different ways to prevent pregnancy.
- It prevents the release of eggs from the ovary (ovulation).
- It makes it difficult for sperm to get to an egg by thickening vaginal fluid.
- It prevents the attachment of a fertilised egg to womb.
Side effects of Microval
The side effects you may experience after taking/inserting Microval include:
- Vaginal bleeding
- Breast pain or tenderness
- Stomach pain
- Headache
- Dizziness
- Tiredness
- Nausea
- Vomiting
- Diarrhoea
- Infections: for IUDs only
You may equally experience other side effects other than those listed above.
Pharmacokinetic properties of Microval
Absorption
Orally administered Microval is rapidly and almost completely absorbed.
The absolute bioavailability of levonorgestrel was determined to be almost 100% of the dose administered.
Distribution
Levonorgestrel is bound to serum albumin and sex hormone binding globulin(SHBG). Only about 1.5% of the total serum levels are present as free steroid. 65% are specifically bound to SHBG.
About 0.1% of the maternal dose can be transferred via milk to the nursed infant.
Biotransformation
The biotransformation follows the known pathways of steroid metabolism, thelevonorgestrel is hydroxylated by liver enzymes mainly by CYP3A4 and itsvmetabolites are excreted after glucuronidation by liver glucuronidase enzymes.
Elimination
After reaching maximum serum levels, the concentration of levonorgestrel decreased with a mean elimination half-life of about 26 hours.
Levonorgestrel is not excreted in unchanged form but as metabolites. Levonorgestrel metabolites are excreted in about equal proportions with urine and faeces.
Pharmacokinetics in obese women
A pharmacokinetic study showed that levonorgestrel concentrations are decreased in obese women (BMI ≥ 30 kg/m²) (approximately 50% decrease in Cmax and AUC0-24), compared to women with normal body mass index.
Is Microval used in pregnancy?
Do not use in pregnancy
Can Microval be used by a breast feeding mother?
Yes. It can be used. It is safe. However, about 0.1% of the maternal dose can be transferred via milk to the nursed infant.
Microval Interactions with Drugs
Enzyme inducers, including CYP3A4, that metabolize progestins may decrease the plasma concentrations and the effectiveness of Microval. These include:
- barbiturates (including primidone)
- bosentan
- carbamazepine
- felbamate
- griseofulvin
- oxcarbazepine
- phenytoin
- rifampin
- St. John’s wort
- topiramate
- Efavirenz
- Protease inhibitors (increase or decrease)
- Non-nucleoside reverse transcriptase inhibitors (increase or decrease)