Lateralized exanthem mimicking figurate inflammatory dermatosis of infancy after methimazole therapy

Methimazole-induced urticaria in hyperthyroid patients: A safe re-administration protocol

PURPOSE

The safety profile of methimazole (MMI) seems to be better than propylthiouracil in the management of hyperthyroidism. It is therefore advisable to use IMM as the first choice in Graves' patients. It is important to keep this drug in patients regardless of minor side effects. We report a case series of MMI-induced urticaria and provide a stepwise protocol for the safe re-administration of MMI.

METHODS

It was a retrospective case series including all patients having manifested urticaria following MMI intake for hyperthyroidism; notified to the Pharmacovigilance Unit of the Clinical Pharmacology Department (March 2013-January 2022).

RESULTS

We have included 11 patients (SR: 0.22). The median time interval between the start of MMI and the onset of urticaria averaged 14.5 days. The median daily dose of MMI was 40mg. MMI was interrupted in all patients. Urticaria has progressively resolved after drug interruption and antihistamine intake. Reintroduction of MMI was performed in 10/11 patients as follows: one quarter of the daily dose on the first day, half of the daily dose on the 4th day, the three quarters of the daily dose on the 7th day, to reach the scheduled total dose on the 10th day. Cetirizine was added at the time of reintroduction and withdrawn 2 weeks later. All the patients were successfully controlled.

CONCLUSION

Given the importance of this drug in the management of hyperthyroidism, MMI should not be withdrawn in cases of urticaria. After the resolution of urticaria, a gradual reintroduction of MMI should be attempted with concomitant antihistamine therapy.

[Adverse reactions of methimazole in children with hyperthyroidism]

OBJECTIVES

To investigate the incidence rate of adverse reactions of methimazole in children with hyperthyroidism.

METHODS

A retrospective analysis was performed on the medical data of 304 children with hyperthyroidism who were hospitalized in Shengjing Hospital of China Medical University from January 2015 to May 2021. The incidence rate of methimazole-related adverse reactions was analyzed. The risk factors for common adverse reactions were evaluated.

RESULTS

Among the 304 children, 87 (28.6%) experienced adverse reactions, among whom there were 20 boys (23%) and 67 girls (77%). Common adverse reactions included neutropenia (12.8%), rash (11.8%), elevated alanine aminotransferase (9.5%), and joint pain (3.0%), and some children experienced multiple adverse reactions simultaneously or intermittently. Neutropenia often occurred within 3 months after administration (25/39, 64%), elevated alanine aminotransferase often occurred within 1 month after administration (17/29, 59%), and rash often occurred within 3 months after administration (30/36, 83%). Most of the above adverse reactions returned to normal after symptomatic treatment. The multivariate logistic regression analysis showed that younger age and lower absolute neutrophil count before treatment were risk factors for neutropenia after methimazole treatment (P<0.05).

CONCLUSIONS

The adverse reactions of methimazole are common in children with hyperthyroidism, and most adverse reactions occur within 3 months after administration and can be relieved after symptomatic treatment. Children with a younger age or a lower baseline absolute neutrophil count may have a higher risk of neutropenia.