INFORMATION FOR HEALTH PROFESSIONALS
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Size No.4 white, hard gelatin capsules containing 2.5mg gestrinone, in a blister pack of eight.
DIMETRIOSE is a synthetic steroid hormone with anti-progestin activity. In vitro, it has weak agonist activity on progesterone receptors in the rabbit endometrium, and progesterone antagonist activity in various other pharmacological test systems.
In addition, it has moderate agonist activity on prostatic androgen receptors in vitro. In various in vivo test systems this activity is found to be low.
DIMETRIOSE has, thus, a weak androgen and progestogen activity. Its main action is on the hypothalamic-pituitary axis where it inhibits gonadotrophin release with a weak inhibitory effect on synthesis. It also possesses anti-oestrogen activity.
The suppression of the ovular gonadotrophin peak is observed after the first month of treatment; the resulting absence of ovarian secretion rapidly leads to endometrial atrophy.
Apart from its anti-hypophyseal action, DIMETRIOSE also has anti-progesterone activity on cell receptors in both endometrium and extra-uterine ectopic implants.
No anti-glucocorticoid activity has been detected in animal studies.
Linear pharmacokinetics are found after oral administration of doses of 1.25mg, 2.5mg or 5mg.
The average peak plasma concentration is 19 µg/L and occurred two to three hours after administration of an oral dose of 2.5mg.
The plasma elimination half-life and the volume of distribution are approximately 27 hours and 67 litres respectively. DIMETRIOSE is bound to plasma albumin.
Three days after administration, plasma levels are only 5% of the peak plasma concentration. A steady state is reached after the second capsule, which is taken three days after the first.
In the normal therapeutic regimen, there is, therefore, no risk of accumulation.
An absolute bioavailability study in a healthy adult showed that gestrinone is completely absorbed after oral administration, and that there is a negligible first pass effect.
DIMETRIOSE is actively metabolised in the liver, essentially by hydroxylation, to conjugated metabolites 16b -hydroxy, 13-ethyl (1-OH) and D-homo gestrinone. About 43% of the dose is excreted in the urine and 33% in the faeces.
Endometriosis with or without accompanying infertility.
Gestrinone is for oral administration only.
The dose is one capsule twice a week. The first dose should always be taken on the first day of the menstrual cycle. The second dose should be taken three days later. Thereafter, gestrinone capsules should be taken on the same two days of the week (preferably at the same time) every week for the duration of
treatment, which should last for six months.
Depending on the judgement of the physician, the dose can be increased to three capsules per week for several weeks, especially when spotting occurs.
In case of missed medication:
Should one dose be missed, then a capsule should be taken as soon as possible and the original sequence maintained.
Should two or more doses be missed, treatment should be discontinued and therapy re-started on the first day of the new cycle, following a negative pregnancy test and according to the usual dosage schedule.
As the oral contraceptive pill can interfere with Dimetriose, barrier contraceptive methods should be used and must be employed for the entire duration of treatment.
The use of gestrinone in the elderly or in children is not envisaged.
Gestrinone at the recommended dose inhibits ovulation in many women but pregnancies do occur with this regimen and gestrinone must not be relied on for contraception . It is essential that barrier methods are used throughout treatment, the use of gestrinone is contraindicated in pregnancy.
Because gestrinone may occasionally cause some degree of fluid retention, patients with cardiac or renal dysfunction require close monitoring.
Monitor ALAT, ASAT, cholesterol fractions in hyperlipidaemic subjects and blood sugar levels in diabetics.
Gestrinone will cause a decrease in the concentration of thyroid-binding globulin. Hence, there will be a decrease in serum total thyroxine levels. This is without clinical significance as free thyroxine levels remain within the reference range as do thyroid-stimulating hormone levels.
Pregnancy must be excluded before starting treatment. Although gestrinone has no teratogenic action in animals, reproduction studies have shown embryotoxic hormonal effects in some species.
Administration of gestrinone is contraindicated.
In the clinical investigations completed to date, the majority of adverse events have been associated with the slight androgenic activity of gestrinone. In almost every case, the symptoms regressed after completion of treatment.
Spotting may occur at the start of treatment, especially if administration is not started on the first day of the menstrual cycle.
Acne, seborrhoea, fluid retention, weight gain, hirsutism, hair loss, decrease in breast size, voice change, and other androgen type effects may occur.
Other undesirable effects:
Concomitant administration of anti-epileptic drugs or Rifampicin may result in accelerated metabolism of gestrinone.
No cases of overdosage due to DIMETRIOSE have so far been reported. Gastric lavage is indicated after ingestion of a massive dose.
Pharmaceutical Precautions
Protect from light. Store below 30°C.
Shelf life is 3 years.
Prescription Medicine.
Blister pack of 8 capsules.
Clinical Laboratory Test Findings
A clinical study showed a significant decrease in HDL cholesterol during treatment. Small increases in red cell count and haemoglobin have been observed.
Hoechst Marion Roussel (NZ) Limited
P O Box 12851
Penrose,
AUCKLAND
Telephone: (09) 5264102
Facsimile (09) 5264109
January 1999