Preparat: Thacapzol®, Thiamazole Uni-Pharma, Tiamazol 2care4, Tiamazol Abacus Medicine, Tiamazol Ebb
ATC kod: H03BB02
Tyreostatika kan orsaka agranulocytos, som enligt vissa studier är vanligare hos kvinnliga patienter.
Tiamazol in English literature is known as methimazole.
No studies with a clinically relevant sex analysis regarding the pharmacokinetics or dosing of methimazole have been found. For both men and women, the lowest effective dose is recommended (see Adverse effects) .
Studies have shown that more men than women fail to enter long-term remission after thyreostatic therapy for Graves’ disease [1,2]. A clinical trial (92 men, 444 women) found that men had a markedly worse outcome after medical treatment with carbimazole (prodrug to methimazole) or propylthiouracil for 18 months. Men had with a remission rate of only 19.5% compared with 40% for females .
Antithyroid drug therapy is associated with agranulocytosis. Among reported cases of antithyroid-induced agranulocytosis, females are in majority [3-5]. Mean doses at onset of agranulocytosis are varying; for methimazole 25-44 mg/day and for propylthiouracil 217-383 mg/day. Although antithyroid-induced agranulocytosis is rare, it has been suggested that low-dose methimazole therapy may be safer than high-dose therapy or treatment with conventional doses of propylthiouracil . The reasons why women are affected more frequently than men are suggested to be due to pharmacokinetic differences between men and women, immunologic and hormonal factors as well as differences in co-medications .
Some epidemiologic studies suggest that methimazole exposure during the first trimester of pregnancy is associated with an increased risk of congenital malformations. Since propylthiouracil has not been associated with an increased risk of congenital malformations, this is the recommended drug during the first trimester during pregnancy . However, propylthiouracil is associated with hepatotoxicity (estimated incidence 0.1-0.2% of exposed adults), and therefore treatment with low-dose methimazole during the second and third trimesters have been suggested by American guidelines , but not in Sweden . Treatment of thyrotoxicosis during pregnancy should always be referred to a specialist. Regarding teratogenic aspects, please consult Janusmed Drugs and Birth Defects (in Swedish, Janusmed fosterpåverkan).
Prescribing practices for methimazole and propylthiouracil in the U.S. between the years 1991-2008 were examined using data from pharmacy databases. Men were more likely to be on methimazole (82%) than women (74%), although 72% of methimazole prescriptions were to women .
Fler kvinnor än män hämtade ut tabletter innehållande tiamazol (ATC-kod H03BB02) på recept i Sverige år 2018, totalt 7 383 kvinnor och 2 013 män. Det motsvarar 1,5 respektive 0,4 personer per tusen invånare. Andelen som hämtat ut läkemedel var högst i åldersgruppen 80 år och äldre hos båda könen. I genomsnitt var tabletter innehållande tiamazol 3,5 gånger vanligare hos kvinnor . Prevalensen av hypertyreos är 2 % hos kvinnor och 0,2 % hos män .
Faktagranskat av: Mia von Euler
Godkänt av: Karin Schenck-Gustafsson