Micronor (Norethindrone)




Oral Contraceptive

Action And Clinical Pharmacology: The mechanism of contraception action of Micronor tablets is multicausal, primarily at the local pelvic level and secondarily at the systemic level. The hormonal effect is mainly progestational.

Pelvic effects include changes in the cervical mucus and endometrium. Systemic effects involve mainly the inhibition of secretion of pituitary gonadotropins which in turn prevents follicular maturation and ovulation.

Studies by Moghissi, Beck, Fortier and Lefebvre, and others suggest the following priority of causes: 1. Inhibitory cervical mucus changes including increased viscosity and cell content, with inhibition of sperm transport or migration. Changes in cervical mucus reach their peak 3 to 4 hours after Micronor pill intake and the possibility of sperm penetration remains low for 16 to 19 hours. 2. Suppression of FSH levels and the LH surge. 3. Abnormal ovulation and deficient corpus luteum function. (Serum progesterone levels may be suppressed in the second half of the menstrual cycle when they are usually low, i.e., dysphasic.) Serum estrogens may be increased above normal early in the cycle. 4. Endometrial changes (progestational) unfavorable to implantation.

Indications And Clinical Uses: Conception control.

Micronor tablets contain a low dosage of norethindrone without the addition of an estrogen agent. Progestin-only pills are often called “Progestin-only pills” or the “Minipill”.

Contra-Indications: Progestin-only pills should not be used by women who currently have the following conditions: when pregnancy is suspected or diagnosed; active liver disease or history of/or actual benign or malignant liver tumors; known or suspected carcinoma of the breast; undiagnosed abnormal vaginal bleeding; hypersensitivity to any component of this product.

Manufacturers’ Warnings In Clinical States: Progestin-only pills have less progestin than the combined birth control pill (or the “Pill”) which contains both an estrogen and a progestin. Therefore, this product monograph does not discuss the serious health risks that have been associated with the estrogen component of combined oral contraceptives (COCs).

Cigarette smoking increases the risk of serious adverse effects on the heart and blood vessels. This risk increases with age and becomes significant in oral contraceptive users over 35 years of age. Women should be counselled not to smoke.

Ectopic Pregnancy: The incidence of ectopic pregnancies for progestin-only oral contraceptive users is 5 per 1 000 woman-years. Up to 10% of pregnancies reported in clinical studies of progestin-only oral contraceptive users are extrauterine. Although symptoms of ectopic pregnancy should be watched for, a history of ectopic pregnancy need not be considered a contraindication to use of this contraceptive method. Health providers should be alert to the possibility of an ectopic pregnancy in women who become pregnant or complain of lower abdominal pain while on progestin-only oral contraceptives.

Delayed Follicular Atresia/Ovarian Cysts: If follicular development occurs, atresia of the follicle is sometimes delayed and the follicle may continue to grow beyond the size it would attain in a normal cycle. Generally these enlarged follicles disappear spontaneously. Often they are asymptomatic; in some cases they are associated with mild abdominal pain. Rarely they may twist or rupture, requiring surgical intervention.

Carcinoma of the Breast and Reproductive Organs: Some epidemiological studies of oral contraceptive users have reported an increased relative risk of developing breast cancer, particularly at a younger age and apparently related to duration of use. These studies have predominately involved combined oral contraceptives and there is insufficient data to determine whether the use of progestin-only pills similarily increases the risk. Women with breast cancer should not use oral contraceptives because the role of female hormones in breast cancer has not been fully determined.

Some studies suggest that oral contraceptive use has been associated with an increase in the risk of cervical intraepithelial neoplasia in some populations of women. However, there continues to be controversy about the extent to which such findings may be due to differences in sexual behavior and other factors. There is insufficient data to determine whether the use of progestin-only pills increases the risk of developing cervical intraepithelial neoplasia.

Headache: Discontinue medication at the earliest manifestation of severe headache of unknown etiology or worsening of pre-existing migraine headache.

Vaginal Bleeding: Irregular menstrual patterns are common among women using progestin-only oral contraceptives. If genital bleeding is suggestive of infection, malignancy or other abnormal conditions, such nonpharmocologic causes should be ruled out. If prolonged amenorrhea occurs, the possibility of pregnancy should be evaluated.


Sexually Transmitted Diseases Birth control pills do not protect against sexually transmitted diseases (STDs), including HIV/AIDS. For protection against STDs, it is advisable to use latex condoms in combination with birth control pills.

Physical Examination and Follow-up: Before oral contraceptives are used, a thorough history and physical examination should be performed, including a blood pressure determination. Breasts, liver, extremities and pelvic organs should be examined. A Papanicolaou smear should be taken if the patient has been sexually active.

The first follow-up visit should be done 3 months after oral contraceptives are prescribed. Thereafter, examinations should be performed at least once a year or more frequently if indicated. At each annual visit, examination should include those procedures that were done at the initial visit as outlined above or per recommendations of the Canadian Workshop on Screening for Cancer of the Cervix. Their suggestion was that, for women who had 2 consecutive negative Pap smears, screening could be continued every 3 years up to the age of 69.

Pregnancy: Oral contraceptives should not be taken by pregnant women. However, if conception accidentally occurs while taking the pill, there is no conclusive evidence that the progestin contained in the oral contraceptive will damage the developing child.

Lactation: If the use of oral contraceptives is initiated after the establishment of lactation, there does not appear to be any effect on the quantity and quality of the milk. There is no evidence that low dose oral contraceptives are harmful to the nursing infant.

No adverse effects have been found on breast-feeding performance or on the health, growth or development of the infant. Small amounts of progestin pass into the breastmilk, resulting in steroid levels in infant plasma of 1 to 6% of the levels of maternal plasma.

Migraine and Headache: The onset or exacerbation of migraine or the development of headache of a new pattern which is recurrent, persistent or severe, requires discontinuation of oral contraceptives and evaluation of the cause.

Carbohydrate and Lipid Metabolism: Some users may experience slight deterioration in glucose tolerance, with increases in plasma insulin, but women with diabetes mellitus who use progestin-only oral contraceptives do not generally experience changes in their insulin requirements. Nonetheless, prediabetic and diabetic women in particular should be carefully monitored while taking progestin-only pills.

Lipid metabolism is occassionally affected in that HDL, HDL2 and apolipoprotein A-I and A-II may be decreased; hepatic lipase may be increased. There is usually no effect on total cholesterol, HDL3, LDL or VLDL.

Emotional Disorders: Patients with a history of emotional disturbances, especially the depressive type, may be more prone to have a recurrence of depression while taking oral contraceptives. In cases of a serious recurrence, a trial of an alternate method of contraception should be made which may help to clarify the possible relationship. Women with premenstrual syndrome (PMS) may have a varied response to oral contraceptives, ranging from symptomatic improvement to worsening of the condition.

Laboratory Tests: The following endocrine tests may be affected by progestin-only oral contraceptive use: sex hormone-binding globulin (SHBG) concentrations may be decreased; thyroxine concentrations may be decreased, due to a decrease in thyroid-binding globulin (TBG).

Results of laboratory tests should be interpreted in the light that the patient is on oral contraceptives. LH and FSH levels are suppressed by the use of oral contraceptives. Wait 2 weeks after discontinuing the use of oral contraceptives before measurements are made.

Tissue Specimens: Pathologists should be advised of oral contraceptive therapy when specimens obtained from surgical procedures and pap smears are submitted for examination.

Return to Fertility: The limited available data indicate a rapid return of normal ovulation and no delay to fertility following discontinuation of progestin-only oral contraceptives.

Amenorrhea: Women having a history of oligomenorrhea, secondary amenorrhea, or irregular cycles may remain anovulatory or become amenorrheic following discontinuation of progestin therapy. Amenorrhea, especially if associated with breast secretion, that continues for 6 months or more after withdrawal, warrants a careful assessment of hypothalamic-pituitary function.

Drug Interactions: The effectiveness of progestin-only pills is reduced by hepatic-inducing drugs such as the anticonvulsants phenytoin, carbamazepine, and barbiturates and the antituberculosis drug rifampin. No significant interaction has been found with broad-spectrum antibiotics (see Table I). It is important to ascertain all drugs that a patient is taking, both prescription and nonprescription, before oral contraceptives are prescribed.

Refer to Oral Contraceptives 1994 (Chapter 8), Health Canada, for possible drug interactions with OC’s.

Micronor Drugs Which May Decrease the Efficacy of Oral Contraceptives Class of Compound Drug Proposed Mechanism Suggested Management

Anticonvulsants Carbamazepine Ethosuximide Phenobarbital Phenytoin Primidone Induction of hepatic microsomal enzymes: Increased binding of progestin to SHBG. Use higher dose OCs (50 g ethinyl estradiol), another drug or another method.

Antituberculosis Rifampin Increased metabolism of progestins. Use another method.

Sedatives and Hypnotics Benzodiazepines Barbiturates Chloral hydrate Glutethimide Meprobamate Induction of hepatic microsomal enzymes. For short course, use additional method or another drug. For long course, use another method or higher dose OCs.

Adverse Reactions: Adverse reactions reported with the use of progestin-only pills include: Menstrual irregularity is the most frequently reported side effect; frequent and irregular bleeding are common, while long duration of bleeding episodes and amenorrhea are less likely; headache, breast tenderness, nausea, and dizziness are increased among progestin-only oral contraceptive users in some studies; androgenic side effects such as acne, hirsutism, and weight gain occur rarely.

Symptoms And Treatment Of Overdose: Symptoms and Treatment: In case of overdose or accidental ingestion by children, the physician should observe the patient closely although generally no treatment is required. Gastric lavage may be utilized if considered necessary. There have been no reports of serious ill effects from overdosage.

Dosage And Administration: Information for the Patient on How to Take Micronor Tablets (Progestin-only Pills):

1. Read these directions:

before you start taking your pills, and

any time you are not sure what to do.

2. Look at your pill pack:

• 28-Pill Pack: 28 active pills (with hormones) taken daily for 28 days.

Also check the pill pack for instructions on (1) where to start and (2) directions to take pills (see package insert for illustrations).

3. You may wish to use a second method of birth control (e.g., latex condoms and spermicidal foam or gel) for the first 48 hours of the first cycle of pill use. This will provide a back-up in case pills are forgotten while you are getting used to taking them.

4. When receiving any medical treatment, be sure to tell your doctor that you are using birth control pills.

5. Many women have spotting or light bleeding or may feel sick to their stomach during the first 3 months on the pill. If you do feel sick, do not stop taking the pill. The problem will usually go away. If it does not go away, check with your doctor or clinic. The most common side effect of progestin-only pills is a change in menstrual bleeding. Your period may be either late or early and you may have some spotting.

6. Missing pills also can cause some spotting or light bleeding, even if you make up the missed pills. You also could feel a little sick to your stomach on the days you take 2 pills to make up for missed pills.

7. If you miss pills at any time, you could get pregnant. The greatest risks for pregnancy are:

when you start a pack late, and

if you are more than 3 hours late in taking your pill or you miss 1 or more pills.

8. Always be sure you have ready:

another kind of birth control (such as latex condoms and spermicidal foam or gel) to use as a back-up method in case you miss a pill, or take it more than 3 hours late, and

an extra, full pack of pills.

9. If you experience vomiting or diarrhea, or if you take some medicines, such as antibiotics, your pills may not work as well. Use a back-up method, such as latex condoms and spermicidal foam or gel, until you can check with your doctor or clinic.

10. If you forget more than 1 pill 2 months in a row, talk to your doctor or clinic about how to make pill-taking easier or about using another method of birth control.

11. If your questions are not answered here, call your doctor or clinic.

When to start the first pack of Progestin-only pills: Be sure to read these instructions:

before you start taking your pills, and

any time you are not sure what to do.

Your Micronor tablets are in a 28 day pill package. With this type of birth control pill, you take 28 pills which contain only one hormone, a progestin.

Starting Progestin-only Pills:

1. The first day of your menstrual period (bleeding) is Day 1 of your cycle. With Micronor, it is best to start your first package of progestin-only pills on the first day of your menstrual period (Day 1)*. Then you simply continue taking one tablet every single day until your VARIDATE DIALPAK Tablet Dispenser is empty. Without missing a day, start taking Micronor from your new VARIDATE DIALPAK Tablet Dispenser.

*If you decide to take your first progestin-only pill on another day, use an additional method of birth control (such as latex condoms and spermicidal foam or gel) everytime you have sex during the next 48 hours.

2. If you have had a miscarriage or an abortion, you can start progestin-only pills the next day.

3. Take 1 pill at the same time every day for 28 days. Begin a new pack the next day, not missing any days on the pills. Your period should occur during the last 7 days of using that pill pack. Micronor Tablets are taken every day – even when you are having some menstrual bleeding.

Follow these steps carefully (see package insert for illustrations): To set the package to the first day of your period insert a coin into the middle slot and turn the inner wheel counterclockwise until that day appears in the window. The example shown is for a Sunday start. Your first green tablet is below the “V” notch as shown. Ensure that the tab marked “Lift Out” is set over this tablet. Break off the tab and begin tablet taking. To take your second and all subsequent tablets, turn the clear outer cover clockwise to the next available tablet. Take 1 tablet every day for 28 days, completing all green tablets. When you take your last tablet, be sure to set your next package for the following day, i.e., last tablet taken Tuesday, set next package for Wednesday. Important: Remember to take a tablet each day without interruption.

If you are breast-feeding:

1. If you are fully breast-feeding (not giving your baby any food or formula), you may start taking your pills 6 weeks after delivery.

2. If you are partially breast-feeding (giving your baby some food or formula), you should start taking your pills 3 weeks after delivery.

If you are switching pills:

1. If you are switching from the combined pills to progestin-only pills, and you were on a 21-day regimen, take the first progestin-only pill the day after you finish the last active combined pill. If you have been on a 28-day regimen, do not take any of the 7 inactive pills from the combined pill pack. You should know that many women have irregular periods after switching to progestin-only pills, but this is normal and to be expected.

2. If you are switching from progestin-only pills to the combined pills, take the first active combined pill on the first day of your period, even if your progestin-only pill pack is not finished.

3. If you are breast-feeding, you can switch to another method of birth control at anytime, except do not switch to the combined pills until you stop breast-feeding or at least until 6 months after delivery.

What to Do During the Month:

1. Take a pill at the same time every day until the pack is empty. Progestin-only pills must be taken at the same time every day since its action is time dependent. Every time you take a pill more than 3 hours late, and especially if you miss a pill, you are more likely to get pregnant.

Try to associate taking your pill with some regular activity like eating a meal or going to bed.

Do not skip pills even if you have bleeding between monthly periods or feel sick to your stomach (nausea).

Do not skip pills even if you do not have sex very often.

2. When you finish a pack:

28 pills: Start the next pack on the next day. Take 1 pill every day. Do not wait any days between packs.

What to Do if You Miss Pills: If you are more than 3 hours late or miss taking your progestin-only pills:

1. Take a missed pill as soon as you remember you missed it.

2. Then go back to taking progestin-only pills at your regular time.

3. But be sure to use a back-up method (such as a condom and/or a spermicide) everytime you have sex for the next 48 hours.

If you are not sure what to do about the pills you have missed, keep taking progestin-only pills and use a back-up method until you can talk to your doctor or clinic.

Always be sure you have on hand:

a back-up method of birth control (such as latex condoms and spermicidal foam or gel) in case you miss pills, and

an extra, full pack of pills.

If you forget more than 1 pill 2 months in a row, talk to your doctor or clinic. Talk about ways to make pill-taking easier or about using another method of birth control.

Information for the Physician: Counselling Issues: The following points should be discussed with prospective users before prescribing progestin-only oral contraceptives:

the necessity of taking pills at the same time every day, including throughout all bleeding episodes.

the need to use a back-up method such as condoms and spermicides for the next 48 hours whenever a progestin-only oral contraceptive is taken 3 or more hours late.

the potential side effects of progestin-only oral contraceptives, particularly menstrual irregularities.

the need to inform the clinician of prolonged episodes of bleeding, amenorrhea or severe abdominal pain.

the importance of using an effective barrier method in addition to progestin-only oral contraceptives if a woman is at risk of contracting or transmitting STDs/HIV.

Availability And Storage: Each green, unscored tablet, with ORTHO 0.35 engraved on each side, contains: norethindrone 0.35 mg. Nonmedicinal ingredients: D&C Yellow No. 10, FD&C Green No. 5 Aluminum Lake, lactose, magnesium stearate, polyvinylpyrrolidone and starch. Tartrazine-free. A 28-day VARIDATE DIALPAK Tablet Dispenser contains a 4-week supply of tablets. Store between 15 and 30°C.

MICRONOR® Janssen-Ortho Norethindrone Oral Contraceptive

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