Pharmacological Action
Microval (levonorgestrel) is thought to have a threefold contraceptive action: Impaired sperm migration; interference with implantation and reduction of corpus luteum function.
Microval's (levonorgestrel) action, believed to be more local than central, without consistently inhibiting ovulation, may interfere to a lesser extent with the hypothalamic-ovarian axis.
Indications
Microval (levonorgestrel) tablets are indicated for the control of fertility.
Dosage and Directions for Use
Microval (levonorgestrel) must be taken exactly as directed and at intervals not exceeding 24 hours. Patients should be instructed to take the tablets at the same time every day, preferably after the evening meal or at bedtime.
The patient begins Microval (levonorgestrel) on day 1 of her menstrual cycle, i.e. the first day of bleeding. One tablet is taken every day at the same time, without interruption, as long as contraception is desired. Tablets should be taken on this continuous daily regimen whether or not bleeding occurs. A mechanical method of contraception should be used until the first fourteen tablets have been taken.
Missed tablets
The risk of pregnancy increases with each tablet missed. If the patient misses one tablet she should be instructed to take it as soon as she remembers and to also take her next tablet at the regular time. If she misses two tablets, she should take one of the missed tablets as soon as she remembers as well as taking her regular tablet for that day at the proper time. In either case, she should use a mechanical method of contraception until fourteen consecutive tablets have been taken. If she has missed one or two tablets and does not have a period within 45 days of her last, she should discontinue Microval (levonorgestrel) and depend upon a mechanical method of contraception until the possibility of pregnancy has been excluded. If more than two tablets have been missed, Microval (levonorgestrel) should be discontinued immediately and a mechanical method of contraception should be used until menses has appeared or the possibility of pregnancy has been excluded. Alternatively, if the patient has taken the tablets correctly and if menses does not appear within 60 days from the last period, a mechanical method of contraception should be substituted until an appropriate diagnostic procedure is performed to exclude the possibility of pregnancy.
Side Effects and Special Precautions
The incidence of diseases of the circulatory system in women using combined oral contraceptives is significantly greater than that of controls, and the mortality is slightly increased. Coronary thrombosis, cerebrovascular incident and venous thrombosis are more likely to occur in women aged 35 years or over, particularly if they have used the contraceptive for longer than five years, if they smoke, it they are obese or if they are hypertensive. Additional risk factors are diabetes mellitus, hypercholesterolaemia and familia hyperlipoproteinaemia. However, the risk of mortality due to oral contraceptives in women under 35 who are in the high-risk group is in general far less than the risk of mortality due to pregnancy.
Hypertension may occur in association with the use of oral contraceptives. Regular blood pressure checks, including a pre-treatment level, are advisable.
Prolonged amenorrhoea following the use of oral contraceptives may occur. The incidence is in the order of 1% of users. Caution is advised where oligomenorrhoea or amenorrhoea have occurred in the past.
Mood changes, mass gain, skin pigmentation, vaginal candidiasis, gall bladder disease, gastro-intestinal irritation and fluid retention may occur.
Case reports have been published of benign hepatic tumours in women on oral contraceptives for a prolonged time, but a causal relationship has not been established. The preparation should be discontinued if persistent upper abdominal pain develops.
Surgery is more likely to be associated with an increased incidence of thrombotic side-effects. Adequate precaution should be taken.
Under no circumstances should the oral contraceptive tablet be stopped without having adopted a satisfactory alternative method of contraception.
Interactions with other drugs and efficacy
The efficacy of the contraceptive pill may be decreased when it is administered concomitantly with other drugs such as anti-epileptic agents, rifampicin, phenylbutazone and ampicillin. With vomiting or diarrhoea, the absorption of oral contraceptives may be diminished and women should be advised to use additional methods of contraception at the time of such disorders.
Effects on laboratory tests
Oral contraceptives may interfere with some laboratory estimations, in particular hormones, glucose tolerance, thyroid function, blood coagulation, serum triglycerides and liver function tests.
Identification
Each pack of Microval (levonorgestrel) contains 28 white, bi-convex, coated tablets.
Presentation
Microval (levonorgestrel) is obtainable in packs of 28 tablets.
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