Table 1.

Suspected adverse drug reactions to oral and transdermal methimazole (modified from [28]).

Side-Effects	Dose Range (Total mg/day)	Administration	Frequency (%)	Time to Onset (Days)	Recommendation	Monitoring/Comments
Hepatopathy	5 to 15 5	Oral Transdermal	2.6 4	15 to 60 14	/	Liver enzymes function
Bleeding diathesis	5 to 15	Oral	2.5	15 to 50	/	In most cases associated with thrombo- cytopenia
Marked thrombocytopenia	5 to 20 10	Oral Transdermal	2.8 8	14 to 90 14 to 28	Discontinue treatment	Platelet counts 2 weeks later
Agranulocytosis neutropenia	5 to 20 5 to 10	Oral Transdermal	2.7 7	26 to 95 Within the first 4 weeks	/	cell blood count two weeks later
Myasthenia gravis	Unknown	Oral	4 cases reported	60 to 120	Discontinue treatment, administer steroids
Anaemia	2.5 to 5	Oral	1 case report	After 3 years of treatment	Discontinue treatment if anaemia is severe, no re- challenge	cell blood count 2 weeks later
Gastro-intestinal upset or lethargy	2.5 to 15	Oral	Vomiting, nausea, 9.3 Anorexia, 8.9 Unspecified GI upset, 23 Lethargy, 10.5	7 to 60 1 to 78 Within the first 4 weeks 1 to 60	Continue treatment Lower dosage if no improvement
Generalized peripheral lymphadenopathy	10	Oral	1 case report	Within 2 weeks	Discontinue treatment
Antinuclear antibodies	2.5 to 20	Oral	23	10 to 870	Not routinely measured
Mild haematological abnormalities	2.5 to 25	Oral	16.4	10 to 490	Continue treatment, unless associated with clinical signs
Positive DAT (Direct Antiglobulin Test)	10 to 15	Oral	1.9	45 to 60	Continue treatment if no haemolytic anaemia
Dermatological reactions (i.e., facial excoriation)	5 to 15 5 to 10	Oral Transdermal	4 8	6 to 40 Within the first 4 weeks	Ideally, discontinuation of treatment is recommended