Favistan

When are you taking this medicine? Empty stomach Before food After food With a meal

Favistan uses

• Description
• Clinical pharmacology
• Indications and usage
• Contraindications
• Warnings
• Precautions
• Adverse reactions
• Overdosage
• Dosage and administration
• How supplied
• Favistan reviews

DESCRIPTION

Favistan^® (Methimazole Tablets, USP) (1-methylimidazole-2-thiol) is a white, crystalline substance that is freely soluble in water. It differs chemically from the drugs of the thiouracil series primarily because it has a 5- instead of a 6-membered ring.

Each tablet contains 5 or 10 mg (43.8 or 87.6 µmol) Favistan, an orally administered antithyroid drug.

Each tablet also contains lactose monohydrate, magnesium stearate, starch (corn), pregelatinized starch and talc.

The molecular weight is 114.16, and the molecular formula is C₄H₆N₂S. The structural formula is as follows:

Chemical Structure

CLINICAL PHARMACOLOGY

Favistan inhibits the synthesis of thyroid hormones and thus is effective in the treatment of hyperthyroidism. The drug does not inactivate existing thyroxine and tri-iodothyronine that are stored in the thyroid or circulating in the blood nor does it interfere with the effectiveness of thyroid hormones given by mouth or by injection.

Favistan is readily absorbed in the gastrointestinal tract, metabolized in the liver, and excreted in the urine.

INDICATIONS AND USAGE

Favistan is indicated:

• In patients with Graves' disease with hyperthyroidism or toxic multinodular goiter for whom surgery or radioactive iodine therapy is not an appropriate treatment option.
• To ameliorate symptoms of hyperthyroidism in preparation for thyroidectomy or radioactive iodine therapy.

CONTRAINDICATIONS

Favistan is contraindicated in the presence of hypersensitivity to the drug or any of the other product components.

WARNINGS

First Trimester Use of Favistan and Congenital Malformations

Favistan crosses the placental membranes and can cause fetal harm, when administered in the first trimester of pregnancy. Rare instances of congenital defects, including aplasia cutis, craniofacial malformations, gastrointestinal malformations (esophageal atresia with or without tracheoesophageal fistula), omphalocele and abnormalities of the omphalomesenteric duct have occurred in infants born to mothers who received Favistan in the first trimester of pregnancy. If Favistan is used during pregnancy or if the patient becomes pregnant while taking this drug, the patient should be warned of the potential hazard to the fetus.

Because of the risk for congenital malformations associated with use of Favistan in the first trimester of pregnancy, it may be appropriate to use other agents in pregnant women requiring treatment for hyperthyroidism. If Favistan is used, the lowest possible dose to control the maternal disease should be given.

Agranulocytosis

Agranulocytosis is potentially a life-threatening adverse reaction of Favistan therapy. Patients should be instructed to immediately report to their physicians any symptoms suggestive of agranulocytosis, such as fever or sore throat. Leukopenia, thrombocytopenia, and aplastic anemia (pancytopenia) may also occur. The drug should be discontinued in the presence of agranulocytosis, aplastic anemia (pancytopenia), ANCA-positive vasculitis, hepatitis, or exfoliative dermatitis and the patient's bone marrow indices should be monitored.

Liver Toxicity

Although there have been reports of hepatotoxicity associated with Favistan, the risk of hepatotoxicity appears to be less with Favistan than with propylthiouracil, especially in the pediatric population. Symptoms suggestive of hepatic dysfunction (anorexia, pruritis, right upper quadrant pain, etc.) should prompt evaluation of liver function (bilirubin, alkaline phosphatase) and hepatocellur integrity (ALT, AST). Drug treatment should be discontinued promptly in the event of clinically significant evidence of liver abnormality including hepatic transaminase values exceeding 3 times the upper limit of normal.

Hypothyroidism

Favistan can cause hypothyroidism necessitating routine monitoring of TSH and free T4 levels with adjustments in dosing to maintain a euthyroid state. Because the drug readily crosses placental membranes, Favistan can cause fetal goiter and cretinism when administered to a pregnant woman. For this reason, it is important that a sufficient, but not excessive, dose be given during pregnancy.

PRECAUTIONS

General

Patients who receive Favistan should be under close surveillance and should be cautioned to report immediately any evidence of illness, particularly sore throat, skin eruptions, fever, headache, or general malaise. In such cases, white-blood-cell and differential counts should be obtained to determine whether agranulocytosis has developed. Particular care should be exercised with patients who are receiving additional drugs known to cause agranulocytosis.

Information for Patients

Patients should be advised that if they become pregnant or intend to become pregnant while taking an antithyroid drug, they should contact their physician immediately about their therapy.

Laboratory Tests

Because Favistan may cause hypoprothrombinemia and bleeding, prothrombin time should be monitored during therapy with the drug, especially before surgical procedures. Thyroid function tests should be monitored periodically during therapy. Once clinical evidence of hyperthyroidism has resolved, the finding of a rising serum TSH indicates that a lower maintenance dose of Favistan should be employed.

Drug Interactions

Anticoagulants

Due to potential inhibition of vitamin K activity by Favistan, the activity of oral anticoagulants (e.g., warfarin) may be increased; additional monitoring of PT/INR should be considered, especially before surgical procedures.

β-adrenergic blocking agents

Hyperthyroidism may cause an increased clearance of beta blockers with a high extraction ratio. A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid.

Digitalis glycosides

Serum digitalis levels may be increased when hyperthyroid patients on a stable digitalis glycoside regimen become euthyroid; a reduced dosage of digitalis glycosides may be needed.

Theophylline

Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.

Carcinogenesis, Mutagenesis, Impairment of Fertility

In a 2 year study, rats were given Favistan at doses of 0.5, 3, and 18 mg/kg/day. These doses were 0.3, 2, and 12 times the 15 mg/day maximum human maintenance dose. Thyroid hyperplasia, adenoma, and carcinoma developed in rats at the two higher doses. The clinical significance of these findings is unclear.

Pregnancy

Pregnancy Category D

See WARNINGS

If Favistan is used during the first trimester of pregnancy or if the patient becomes pregnant while taking this drug, the patient should be warned of the potential hazard to the fetus.

In pregnant women with untreated or inadequately treated Graves' disease, there is an increased risk of adverse events of maternal heart failure, spontaneous abortion, preterm birth, stillbirth and fetal or neonatal hyperthyroidism.

Because Favistan crosses placental membranes and can induce goiter and cretinism in the developing fetus, hyperthyroidism should be closely monitored in pregnant women and treatment adjusted such that a sufficient, but not excessive, dose be given during pregnancy. In many pregnant women, the thyroid dysfunction diminishes as the pregnancy proceeds; consequently, a reduction of dosage may be possible. In some instances, anti-thyroid therapy can be discontinued several weeks or months before delivery.

Due to the rare occurrence of congenital malformations associated with Favistan use, it may be appropriate to use an alternative anti-thyroid medication in pregnant women requiring treatment for hyperthyroidism particularly in the first trimester of pregnancy during organogenesis.

Given the potential maternal adverse effects of propylthiouracil, it may be preferable to switch from propylthiouracil to Favistan for the second and third trimesters.

Nursing Mothers

Favistan is present in breast milk. However, several studies found no effect on clinical status in nursing infants of mothers taking Favistan. A long-term study of 139 thyrotoxic lactating mothers and their infants failed to demonstrate toxicity in infants who are nursed by mothers receiving treatment with Favistan. Monitor thyroid function at frequent (weekly or biweekly) intervals.

Pediatric Use

Because of postmarketing reports of severe liver injury in pediatric patient treated with propylthiouracil, Favistan is the preferred choice when an antithyroid drug is required for a pediatric patient.

ADVERSE REACTIONS

Major adverse reactions (which occur with much less frequency than the minor adverse reactions) include inhibition of myelopoieses (agranulocytosis, granulocytopenia, thrombocytopenia, and aplastic anemia), drug fever, a lupus-like syndrome, insulin autoimmune syndrome (which can result in hypoglycemic coma), hepatitis (jaundice may persist for several weeks after discontinuation of the drug), periarteritis, and hypoprothrombinemia. Nephritis occurs very rarely.

Minor adverse reactions include skin rash, urticaria, nausea, vomiting, epigastric distress, arthralgia, paresthesia, loss of taste, abnormal loss of hair, myalgia, headache, pruritus, drowsiness, neuritis, edema, vertigo, skin pigmentation, jaundice, sialadenopathy, and lymphadenopathy.

OVERDOSAGE

Signs and Symptoms

Symptoms may include nausea, vomiting, epigastric distress, headache, fever, joint pain, pruritus, and edema. Aplastic anemia or agranulocytosis may be manifested in hours to days. Less frequent events are hepatitis, nephrotic syndrome, exfoliative dermatitis, neuropathies, and CNS stimulation or depression. No information is available on the median lethal dose of the drug or the concentration of Favistan in biologic fluids associated with toxicity and/or death.

Treatment

To obtain up-to-date information about the treatment of overdose, a good resource is your certified Regional Poison Control Center. In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in the patient.

In the event of an overdose, appropriate supportive treatment should be initiated as dictated by the patient's medical status.

DOSAGE AND ADMINISTRATION

Favistan is administered orally. The total daily dosage is usually given in 3 divided doses at approximately 8-hour intervals.

Adult

The initial daily dosage is 15 mg for mild hyperthyroidism, 30 to 40 mg for moderately severe hyperthyroidism, and 60 mg for severe hyperthyroidism, divided into 3 doses at 8-hour intervals. The maintenance dosage is 5 to 15 mg daily.

Pediatric

Initially, the daily dosage is 0.4 mg/kg of body weight divided into 3 doses and given at 8-hour intervals. The maintenance dosage is approximately 1/2 of the initial dose.

HOW SUPPLIED

Favistan Tablets are available in:

The 5-mg tablets are round, white to off-white, scored on one side and the other side debossed with "J94".

They are available as follows:

Bottles of 100 NDC 60793-104-01

The 10-mg tablets are round, white to off-white, scored on one side and the other side debossed with "J95".

They are available as follows:

Bottles of 100 NDC 60793-105-01

Store at controlled room temperature, 15° to 30°C (59° to 86°F).

Manufactured by: AAI Pharma, 1726 North 23rd St., Wilmington, NC 28405

LAB-0602-2.0

December 2015

Logo

Pfizer

NDC 60793-104-01

Favistan ^®

Favistan Tablets, USP

5 mg

100 TABLETS

Rx only

Pfizer

NDC 60793-105-01

Favistan ^®

Favistan Tablets, USP

10 mg

100 TABLETS

Rx only

Favistan pharmaceutical active ingredients containing related brand and generic drugs:

• Methimazole

Favistan available forms, composition, doses:

• N/A

Favistan destination | category:

• Human:
• Antithyroid agents
• Thyroid hormones

Favistan Anatomical Therapeutic Chemical codes:

• H03BB02 - Thiamazole

Favistan pharmaceutical companies:

• Asta Medica
• Biochemie
• Sandoz
• Temmler Pharma

References

1. Dailymed."TAPAZOLE (METHIMAZOLE) TABLET [PFIZER LABORATORIES DIV PFIZER INC]". https://dailymed.nlm.nih.gov/dailym... (accessed August 28, 2018).
2. Dailymed."METHIMAZOLE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailym... (accessed August 28, 2018).
3. "methimazole". https://pubchem.ncbi.nlm.nih.gov/co... (accessed August 28, 2018).

Frequently asked Questions

Can i drive or operate heavy machine after consuming Favistan?

Depending on the reaction of the Favistan after taken, if you are feeling dizziness, drowsiness or any weakness as a reaction on your body, Then consider Favistan not safe to drive or operate heavy machine after consumption. Meaning that, do not drive or operate heavy duty machines after taking the capsule if the capsule has a strange reaction on your body like dizziness, drowsiness. As prescribed by a pharmacist, it is dangerous to take alcohol while taking medicines as it exposed patients to drowsiness and health risk. Please take note of such effect most especially when taking Primosa capsule. It's advisable to consult your doctor on time for a proper recommendation and medical consultations.

Is Favistan addictive or habit forming?

Medicines are not designed with the mind of creating an addiction or abuse on the health of the users. Addictive Medicine is categorically called Controlled substances by the government. For instance, Schedule H or X in India and schedule II-V in the US are controlled substances.

Please consult the medicine instruction manual on how to use and ensure it is not a controlled substance.In conclusion, self medication is a killer to your health. Consult your doctor for a proper prescription, recommendation, and guidiance.

Review

sdrugs.com conducted a study on Favistan, and the result of the survey is set out below. It is noteworthy that the product of the survey is based on the perception and impressions of the visitors of the website as well as the views of Favistan consumers. We, as a result of this, advice that you do not base your therapeutic or medical decisions on this result, but rather consult your certified medical experts for their recommendations.

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The information was verified by Dr. Rachana Salvi, MD Pharmacology