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Metopirone
T2005-01
Metopirone®
metyrapone USP
Capsules
Diagnostic Test of Pituitary
Adrenocorticotropic Function
Rx only
Prescribing Information
DESCRIPTION
Metopirone, metyrapone USP, is an inhibitor of endogenous adrenal corticosteroid synthesis, available as 250-mg capsules for oral administration. Its chemical name is 2-methyl-1, 2-di-3-pyridyl-1-propanone, and its structural formula is
Metyrapone USP is a white to light amber, fine, crystalline powder, having a characteristic odor. It is sparingly soluble in water, and soluble in methanol and in chloroform. It forms water-soluble salts with acids. Its molecular weight is 226.28.
Inactive Ingredients. Polyethylene glycol, glycerine, gelatin, sodium ethyl hydroxybenzoate, sodium propyl hydroxybenzoate, ethyl vanillin, 4-methoxyacetophenone, titanium dioxide, brown ink.
CLINICAL PHARMACOLOGY
Pharmacodynamics
The pharmacological effect of Metopirone is to reduce cortisol and corticosterone production by inhibiting the 11-β-hydroxylation reaction in the adrenal cortex. Removal of the strong inhibitory feedback mechanism exerted by cortisol results in an increase in adrenocorticotropic hormone (ACTH) production by the pituitary. With continued blockade of the enzymatic steps leading to production of cortisol and corticosterone, there is a marked increase in adrenocortical secretion of their immediate precursors, 11-desoxycortisol and desoxycorticosterone, which are weak suppressors of ACTH release, and a corresponding elevation of these steroids in the plasma and of their metabolites in the urine. These metabolites are readily determined by measuring urinary 17-hydroxycorticosteroids (17-OHCS) or 17-ketogenic steroids (17-KGS). Because of these actions, Metopirone is used as a diagnostic test, with urinary 17-OHCS measured as an index of pituitary ACTH responsiveness. Metopirone may also suppress biosynthesis of aldosterone, resulting in a mild natriuresis.
Pharmacokinetics
The response to Metopirone does not occur immediately. Following oral administration, peak steroid excretion occurs during the subsequent 24-hour period.
INDICATIONS AND USAGE
Metopirone is a diagnostic drug for testing hypothalamic-pituitary ACTH function.
CONTRAINDICATIONS
Metopirone is contraindicated in patients with adrenal cortical insufficiency, or hypersensitivity to Metopirone or to any of its excipients.
WARNINGS
Metopirone may induce acute adrenal insufficiency in patients with reduced adrenal secretory capacity.
PRECAUTIONS
General
Ability of adrenals to respond to exogenous ACTH should be demonstrated before Metopirone is employed as a test. In the presence of hypo- or hyperthyroidism, response to the Metopirone test may be subnormal.
Since Metopirone may cause dizziness and sedation, patients should exercise caution when driving or operating machinery.
Laboratory Tests
See INTERPRETATION.
Drug Interactions
Drugs affecting pituitary or adrenocortical function, including all corticosteroid therapy, must be discontinued prior to and during testing with Metopirone.
The metabolism of Metopirone is accelerated by phenytoin; therefore, results of the test may be inaccurate in patients taking phenytoin within two weeks before. A subnormal response may occur in patients on estrogen therapy.
Metopirone inhibits the glucuronidation of acetaminophen and could possibly potentiate acetaminophen toxicity.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Long-term carcinogenicity and reproduction studies in animals have not been conducted.
Pregnancy Category C
A subnormal response to Metopirone may occur in pregnant women. Animal reproduction studies have not been conducted with Metopirone. The Metopirone test was administered to 20 pregnant women in their second and third trimester of pregnancy and evidence was found that the fetal pituitary responded to the enzymatic block. It is not known if Metopirone can affect reproduction capacity. Metopirone should be given to a pregnant woman only if clearly needed.
Nursing Mothers
It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Metopirone is administered to a nursing woman.
Pediatric Use
See DOSAGE AND ADMINISTRATION.
Geriatric Use
Clinical studies of Metopirone did not include sufficient numbers of subjects aged 65 years and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
ADVERSE REACTIONS
Gastrointestinal System: Nausea, vomiting, abdominal discomfort or pain.
Central Nervous System: Headache, dizziness, sedation.
Dermatologic System: Allergic rash.
Hematologic System: Rarely, decreased white blood cell count or bone marrow depression.
OVERDOSAGE
Acute Toxicity
One case has been recorded in which a 6-year-old girl died after two doses of Metopirone, 2 g.
Oral LD50 in animals (mg/kg): rats, 521; maximum tolerated intravenous dose in one dog, 300.
Signs and Symptoms
The clinical picture of poisoning with Metopirone is characterized by gastrointestinal symptoms and by signs of acute adrenocortical insufficiency.
Cardiovascular System: Cardiac arrhythmias, hypotension, dehydration.
Nervous System and Muscles: Anxiety, confusion, weakness, impairment of consciousness.
Gastrointestinal System: Nausea, vomiting, epigastric pain, diarrhea.
Laboratory Findings: Hyponatremia, hypochloremia, hyperkalemia.
Combined Poisoning
In patients under treatment with insulin or oral antidiabetics, the signs and symptoms of acute poisoning with Metopirone may be aggravated or modified.
Treatment
There is no specific antidote. Besides general measures to eliminate the drug and reduce its absorption, a large dose of hydrocortisone should be administered at once, together with saline and glucose infusions.
Surveillance: For a few days blood pressure and fluid and electrolyte balance should be monitored.
DOSAGE AND ADMINISTRATION
Single-Dose Short Test
This test, usually given on an outpatient basis, determines plasma 11-desoxycortisol and/or ACTH levels after a single dose of Metopirone. The patient is given 30 mg/kg (maximum 3 g Metopirone) at midnight with yogurt or milk. The same dose is recommended in children. The blood sample for the assay is taken early the following morning (7:30-8:00 a.m.). The plasma should be frozen as soon as possible. The patient is then given a prophylactic dose of 50 mg cortisone acetate.
Multiple-Dose Test
Day 1: Control period - Collect 24-hour urine for measurement of 17-OHCS or 17-KGS.
Day 2: ACTH test to determine the ability of adrenals to respond - Standard ACTH test such as infusion of 50 units ACTH over 8 hours and measurement of 24-hour urinary steroids. If results indicate adequate response, the Metopirone test may proceed.
Day 3-4: Rest period.
Day 5: Administration of Metopirone: Recommended with milk or snack.
Adults: 750 mg orally, every 4 hours for 6 doses. A single dose is approximately equivalent to 15 mg/kg.
Children: 15 mg/kg orally every 4 hours for 6 doses. A minimal single dose of 250 mg is recommended.
Day 6: After administration of Metopirone - Determination of 24-hour urinary steroids for effect.
ACTH Test
The normal 24-hour urinary excretion of 17-OHCS ranges from 3 to 12 mg. Following continuous intravenous infusion of 50 units ACTH over a period of 8 hours, 17-OHCS excretion increases to 15 to 45 mg per 24 hours.
HOW SUPPLIED
Capsules 250 mg -- soft gelatin, white to yellowish-white, oblong, opaque, imprinted CIBA on one side and LN on the other side in brown ink.
Bottles of 18………………………………………………………………NDC 0078-0455-17
Do not store above 30ºC (86ºF).
Protect from moisture and heat.
Dispense in tight container (USP).
T2005-01
REV: AUGUST 2005 Printed in U.S.A. 5000178
Manufactured by:
R.P. Scherer GmbH
Eberbach/Baden, Germany
Distributed by:
Novartis Pharmaceuticals Corporation
East Hanover, New Jersey 07936
© Novartis