Antithyroid drugs adverse effects

Discuss the pharmacotherapy of Graves disease, including the advantages and disadvantages of antithyroid drugs versus radioactive iodine, adverse effects, and patient monitoring. 

Agranulocytosis is one of the most serious adverse effects of antithyroid drug therapy. 

Monitor patients on antithyroid drugs for signs and symptoms of adverse effects. 

Neutropenia, agranulocytosis, aplastic anemia, and thrombocytopenia are the most important adverse effects of antithyroid drugs. 

Aplastic anemia due to antithyroid drugs is very rare and has been said to occur as an adverse effect of thionamide therapy with about one-tenth of the frequency of agranulocytosis. 

Bartalena L, Bogazzi F, Martino E. Adverse effects of thyroid hormone preparations and antithyroid drugs. Drug Saf 1996 15(l) 53-63. 

Wing SS, Fantus IG. Adverse immunologic effects of antithyroid drugs. CMAJ 1987 136(2) 121-7. 

Antithyroid drugs for long-term therapy (C). Thiourea-derivatives (thioamides) inhibit peroxidase and, hence, hormone synthesis. To restore a euthyroid state, two therapeutic principles can be applied in Graves disease (a) monotherapy with a thioamide, with gradual dose reduction as the disease abates (b) administration of high doses of a thioamide, with concurrent administration of thyroxine to offset diminished hormone synthesis. Adverse effects of thioamides are rare, but the possibility of agranulocytosis has to be kept in mind. 

Antithyroid drugs Noninvasive Lower initial cost Low risk of permanent hypothyroidism Possible remissions due to immune effects Low cure rate (30%-80% average 40%-50%) Adverse drug reactions Drug compliance Lirst-line treatment in children, adolescents, and in pregnancy Initial treatment in severe cases or preoperative preparation... 

Perhaps one of the most common side effects is a benign transient leukopenia characterized by a white blood cell (WBC) count of less than 4000/mm. This condition occurs in up to 12% of adults and 25% of children, and sometimes can be confused with mild leukopenia seen in Graves disease. This mild leukopenia is not a harbinger of the more serious adverse effect of agranulocytosis, so therapy can usually be continued. If a minor adverse reaction occurs with one antithyroid drug, the alternate thiourea may be tried, but cross-sensitivity occurs in about 50% of patients. ... 

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