Norvetal

Uses

Levonorgestrel is an emergency contraceptive pill for women. Levonorgestrel should be used within 72 hours of unprotected intercourse. It should not be taken as regular birth control pill. This medicine is also known as morning after pill. Levonorgestrel belongs to a group of medicines called progestogen.

This contraception is used as soon as possible, preferably within 12 hours and no later than 72 hours (3 days) after the unprotected sexual intercourse, particularly. If you have had a sexual intercourse whereas either yourself or your partner did not use a contraceptive method

• If you have forgotten to take consecutive 3 regular contraceptive pills
• If your partner’s condom has broken, slipped or been improperly removed or if he has forgotten to use it
• If you fear that your intrauterine device has been expelled
• If your vaginal diaphragm or your contraceptive cap has moved or if have removed it too easily
• If you are afraid that the method of coitus interruptus has failed or if you have had sexual intercourse during the period when you are supposed to be fertile while using the rhythm method
• In the event of rape

Norvetal is also used to associated treatment for these conditions: Endometrial Hyperplasia, Endometriosis, Hypermenorrhea, Postmenopausal Osteoporosis, Pregnant State, Moderate Menopausal Vasomotor Symptoms, Severe Vasomotor Symptoms Associated With Menopause, Emergency Contraception

How Norvetal works

Mechanism of action on ovulation

Oral contraceptives containing levonorgestrel suppress gonadotropins, inhibiting ovulation. Specifically, levonorgestrel binds to progesterone and androgen receptors and slows the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. This process results in the suppression of the normal physiological luteinizing hormone (LH) surge that precedes ovulation. It inhibits the rupture of follicles and viable egg release from the ovaries. Levonorgestrel has been proven to be more effective when administered before ovulation.

Mechanism of action in cervical mucus changes

Similar to other levonorgestrel-containing contraceptives, the intrauterine (IUD) forms of levonorgestrel likely prevent pregnancy by increasing the thickness of cervical mucus, interfering with the movement and survival of sperm, and inducing changes in the endometrium, where a fertilized ovum is usually implanted. Levonorgestrel is reported to alter the consistency of mucus in the cervix, which interferes with sperm migration into the uterus for fertilization. Levonorgestrel is not effective after implantation has occurred. Interestingly, recent evidence has refuted the commonly believed notion that levonorgestrel changes the consistency of cervical mucus when it is taken over a short-term period, as in emergency contraception. Over a long-term period, however, levonorgestrel has been proven to thicken cervical mucus. The exact mechanism of action of levonorgestrel is not completely understood and remains a topic of controversy and ongoing investigation.

Effects on implantation*

The effects of levonorgestrel on endometrial receptivity are unclear, and the relevance of this mechanism to the therapeutic efficacy of levonorgestrel is contentious. Prescribing information for levonorgestrel IUDs state that they exert local morphological changes to the endometrium (e.g. stromal pseudodecidualization, glandular atrophy) that may play a role in their contraceptive activity.

Mechanism of action in hormone therapy

When combined with estrogens for the treatment of menopausal symptoms and prevention of osteoporosis, levonorgestrel serves to lower the carcinogenic risk of unopposed estrogen therapy via the inhibition of endometrial proliferation. Unregulated endometrial proliferation sometimes leads to endometrial cancer after estrogen use.

Dosage

Norvetal dosage

levonorgestrel 0.75 mg Tablets should be taken at the same time, orally, as soon as possible but within 72 hours after unprotected intercourse. The total dosage for one complete regimen of levonorgestrel consists in a single dose of 1.50 mg levonorgestrel.

Levonorgestrel 1.5 mg Tablets should be taken as soon as possible, preferably within 12 hours, and no later than 72 hours (3 days) after having unprotected sex. Levonorgestrel 1.5 mg tablets can be taken at any time in the menstrual cycle assuming the person is not already pregnant. The tablet should not be chewed but should be swallowed whole with water. If a regular method of contraception, such as the contraceptive pill, is already being used, this can be continued at the regular times. If unprotected intercourse takes place again after the use of Levonorgestrel 1.5 mg tablets (also if this is during the same menstrual cycle), the tablet will not exert its contraceptive effect and there is again the risk of pregnancy.

Levonorgestrel can be taken at any moment during the menstrual cycle. After using an emergency contraception, it is recommended to use a local contraceptive mean (condom, spermicide, cervical cap) until the next menstrual period resume.

The use of Levonorgestrel does not contraindicate the continuation of regular hormonal contraception. If you have used this medicine while you were using an oral contraception (contraceptive pill), you should carry on taking the usual tablets until the end of the treatment. In case no menstrual period occurs in the next pill free period following the use of Levonorgestrel, a pregnancy test should be performed to rule out a pregnancy.

One tablet should be taken orally with a glass of water.

Side Effects

Undesirable effects which have been observed are:

• Nausea and vomiting
• Dizziness, fatigue, headache
• Abdominal pain
• A feeling of breast tenderness
• Bleeding can occur after taking this medicine

Inform doctor of any unwanted effect which is not mentioned here

Toxicity

The oral LD50 in rats is greater than 5000 mg/kg.

An overdose of this drug, like other contraceptives, may cause nausea and withdrawal bleeding. Provide symptomatic treatment in the case of a levonorgestrel overdose and contact the local poison control center. There is no specific antidote for a levonorgestrel overdose.

Precaution

Emergency contraception must be used exceptionally, since

• It does not allow to prevent a pregnancy in every instance
• The associated hormonal overdosing is not advisable in case of regular intake
• It cannot replace a regular contraception

After taking Levonorgestrel, menstrual period usually occurs at the expected date nevertheless, it can occur earlier or later by a few days. After taking this tablet, it is therefore mandatory to check the absence of pregnancy by performing a pregnancy test in case of abnormal bleeding at the date of expected period or in case of menstrual delay of more than 5 days. The use of emergency contraception does not replace the necessary precautions against sexually transmitted diseases and the measures to be taken in case of risk of transmission. If vomiting would occur within 2 hours after taking this medicine it is recommended to take immediately another Levonorgestrel tablet.

Interaction

Simultaneous administration of certain anticonvulsant agents (phenobarbiton, phenytoin, primidone, carbamazepin), also other medications such as rafimpicin and griseofulvin can reduce or suppress the effectiveness of this emergency contraception.

Volume of Distribution

One pharmacokinetic study determined a mean steady-state volume of distribution of 1.5 mg of levonorgestrel to be 162.2 L in those with normal BMI and in the range of 404.7 L to 466.4 L in obese patients with a body mass index of at least 30. Mean volume of distribution in 16 patients receiving 0.75 mg of levonorgestrel in another pharmacokinetic study was 260 L. The Plan B one-step FDA label reports an apparent volume of distribution of 1.8 L/kg.

Elimination Route

Orally administered levonorgestrel is absorbed in the gastrointestinal tract while levonorgestrel administered through an IUD device is absorbed in the endometrium. Levonorgestrel is absorbed immediately in the interstitial fluids when it is inserted as a subdermal implant. After insertion of the subdermal implant, the Cmax of levonorgestrel is attained within 2-3 days.The Cmax following one dose of 0.75 mg of oral levonorgestrel is reached within the hour after administration, according to one reference. In a pharmacokinetic study of 1.5 mg of levonorgestrel in women with a normal BMI and those considered to be obese (BMI>30), mean Cmax was found to be 16.2 ng/mL and 10.5 ng/mL respectively. Tmax was found to be 2 hours for those with normal BMI and 2.5 hours for patients with increased BMI. The bioavailability of levonorgestrel approaches 100%.

Mean AUC has been shown to be higher in patients with a normal BMI, measuring at 360.1 h × ng/mL versus a range of 197.28 to 208.1 h × ng/mL in an obese group of patients. Obesity may contribute to decreased efficacy of levonorgestrel in contraception.

Half Life

The elimination half-life of a 0.75 mg dose of 1.5 mg of levonorgestrel ranges between 20-60 hours post-administration. A pharmacokinetic study of women with a normal BMI and BMI over revealed an elimination half-life of 29.7 h and 41.0-46.4 hours, respectively. Another pharmacokinetic study revealed a mean elimination half-life of 24.4 hours after a 0.75 mg dose of levonorgestrel was administered to 16 patients.

Clearance

Clearance was found to 4.8 L/h in healthy female volunteers with a normal BMI, and 7.70-8.51 L/h in obese patients after a single 1.5 mg dose. After a 0.75 mg dose of levonorgestrel in 16 patients in another pharmacokinetic study, mean clearance was calculated at 7.06 L/h. Following levonorgestrel implant removal, the serum concentration falls below 100 pg/mL within the first 96 hours and further falls below the sensitivity of detection within the range of 5 days to 2 weeks.

Elimination Route

Approximately 45% of an oral levonorgestrel dose and its conjugated or sulfate metabolites are found to be excreted in the urine. Approximately 32% of an orally ingested dose is found excreted in feces, primarily in the form of glucuronide conjugates of levonorgestrel.

Pregnancy & Breastfeeding use

The medicine is not indicated in case of pre-existing pregnancy and cannot interrupt it in case of failure of this contraceptive mean with persisting pregnancy. Epidemiological studies indicates no adverse effects of progestogen on malformation of a fetus. Lactation is possible. However, since Levonorgestrel is secreted into breast milk it is suggested that you breast feed immediately before taking each tablet and that you skip nursing following each Levonorgestrel tablet administration.

Contraindication

If you have hypersensitivity to Levonorgestrel.

Acute Overdose

No acute toxicity has been demonstrated with this medicine in case of intake of several doses

Storage Condition

Store in a cool & dry place, protected from light. Keep out of reach of children

Innovators Monograph

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