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Methimazole (Tapazole) and Alcohol: Full Interaction Profile

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At a glance

  • Drug / methimazole, a thionamide tablet that blocks thyroid hormone synthesis [1]
  • Brand status / Tapazole products are listed as discontinued, while current FDA-approved methimazole products are generic oral tablets [1][3]
  • Main shared concern / liver injury; a 2014 review lists alcohol among factors involved in antithyroid-drug liver damage [2]
  • Label liver warning / hepatotoxicity including acute liver failure [1]
  • Label blood warning / agranulocytosis is potentially life-threatening [1]
  • Label drug interaction / warfarin, via possible inhibition of vitamin K activity [1]

Is There a Direct Interaction Between Methimazole and Alcohol?

Methimazole inhibits the synthesis of thyroid hormones and does not inactivate thyroxine or triiodothyronine already stored in the thyroid or circulating in the blood [1]. It is readily absorbed from the gut, metabolized in the liver and excreted in the urine [1].

The interaction the label describes is with warfarin: methimazole may inhibit vitamin K activity and increase the anticoagulant effect, and the label says to consider extra PT/INR monitoring, especially before surgery [1].

The evidence on this page does not show how drinking changes the way the body handles methimazole. That is an evidence gap, not a finding of safety.

The Liver Is Where the Two Overlap

The label reports hepatotoxicity including acute liver failure, and says the risk appears to be less with methimazole than with propylthiouracil, especially in the pediatric population [1]. The label says that symptoms such as anorexia, itching or right upper quadrant pain should prompt evaluation of liver function (bilirubin, alkaline phosphatase, ALT and AST), and that treatment should be discontinued promptly if there is clinically significant liver abnormality, including transaminases above 3 times the upper limit of normal [1].

A 2014 review of liver injury from antithyroid drugs lists alcohol consumption among the factors involved in enhancing the hepatic damage these drugs can cause, and notes that the mechanism of that injury is not fully recognized [2].

Does Alcohol Change Thyroid Function or Thyroid Tests?

The label calls for routine monitoring of TSH and free T4, with dose adjustments to maintain a euthyroid state [1].

One older study, not in methimazole patients, compared 21 chronic alcoholics (more than 100 g of alcohol a day for more than 5 years, all without cirrhosis) with matched controls. Median thyroid volume was 13 mL versus 27 mL, serum T3 and free T3 index were reduced, and T4, free T4 index and TSH were unchanged [4]. In that group the differences were thyroid size and T3, not TSH.

Agranulocytosis and Heavy Drinking

The label calls agranulocytosis potentially life-threatening and says patients should immediately report fever or sore throat to their physicians; leukopenia, thrombocytopenia and aplastic anemia may also occur [1].

Separately, a review reports that heavy alcohol consumption can cause generalized suppression of blood cell production and interferes with the production and function of white blood cells [5]. That review was not about methimazole.

Frequently asked questions

Can you drink alcohol while taking methimazole?
No direct interaction is established. The overlap is the liver: the label reports hepatotoxicity including acute liver failure [1], and a 2014 review lists alcohol consumption among the factors involved in enhancing antithyroid-drug liver damage [2]. Heavy drinking also suppresses blood cell production [5], and the label calls methimazole-related agranulocytosis potentially life-threatening [1].
Does alcohol change thyroid tests while on methimazole?
In one study of 21 chronic alcoholics without cirrhosis, who were not described as taking methimazole, TSH and T4 were unchanged while T3 and free T3 index were lower and thyroid volume was smaller than in matched controls [4]. The label adjusts methimazole dosing on TSH and free T4 [1].
Does heavy drinking affect blood cells?
A review reports that heavy drinking can suppress blood cell production and interfere with white blood cell production and function [5]. Separately, the label calls methimazole-related agranulocytosis potentially life-threatening and says patients should report fever or sore throat immediately [1].
Is methimazole hard on the liver?
The label reports hepatotoxicity including acute liver failure, and says the risk appears to be less with methimazole than with propylthiouracil [1]. It says treatment should be discontinued promptly if transaminases exceed 3 times the upper limit of normal [1].

References

  1. U.S. National Library of Medicine, DailyMed. Methimazole tablets USP (Chartwell RX) prescribing information. Methimazole tablets USP (Chartwell RX) label
  2. Heidari R, Niknahad H, Jamshidzadeh A, Abdoli N. Factors affecting drug-induced liver injury: antithyroid drugs as instances. Clin Mol Hepatol. 2014;20(3):237-48. Factors affecting drug-induced liver injury: antithyroid drugs as instances
  3. Drugs@FDA: FDA-Approved Drugs. Drugs@FDA: FDA-Approved Drugs
  4. Hegedüs L, Rasmussen N, Ravn V, Kastrup J, Krogsgaard K, Aldershvile J. Independent effects of liver disease and chronic alcoholism on thyroid function and size: the possibility of a toxic effect of alcohol on the thyroid gland. Metabolism. 1988;37(3):229-33. Independent effects of liver disease and chronic alcoholism on thyroid function and size: the possibility of a toxic effect of alcohol on the thyroid gland
  5. Ballard HS. The hematological complications of alcoholism. Alcohol Health Res World. 1997;21(1):42-52. The hematological complications of alcoholism
Evidence overview for interactions methimazole: Methimazole (Tapazole) and Alcohol: Full Interaction Profile