This refers to the idiosynchratic reaction which can occur with any anti-thyroid drugs, and is characterised by neutropaenia or agranulocytosis.
Competely asymptomatic neutropaenia requires the causative drug to be stopped, and the counts monitored closely, but usually full recovery occurs without specific therapy.
These are the typical warning signs of possible agranulcytosis. All patients should receive written and verbal warnings to look out for these on starting anti thyroid drugs.
If a patient develops these symptoms, they must be told to stop their anti thyroid drug immediately, and have a full blood count tested urgently. They should only restart their therapy if their blood count is confirmed to be normal.
If the patient's thyrotoxicosis is well controlled, then anti thyroid treatment can be safely discontinued until the agranulocytosis has improved, at which definitive treatment with radioacitve iodine or surgery can be planned.
If the patient is still obviously toxic, they will require beta blockade to control their symptoms during the acute period until they can safely undergo a definitive treatment.
If the patient is very unwell, the possibility of storm should be considered, and if necessary appropriate treatment started e.g. with steroids and Lugol's iodine.
It is useful to assess the cause and duration of thyrotoxicosis as this may affect alternative treatment choices e.g. newly diagnosed severe Graves disease demands urgent treatment, while treatment can be safely interupted in long standing subclinical thyrotoxicosis from a multinodular goitre.
Agranulocytosis is an idiosynchratic reaction, which usually occurs soon after starting anti thyroid drugs, and is most commonly seen in patients on higher doses.
Agranulocytosis is an idiosynchratic reaction, which usually occurs soon after starting anti thyroid drugs, and is most commonly seen in patients on higher doses.
Check all of the patient's medication history as well as their anti-thyroid drug history in case of other agents that may be associated with agranulocytosis.
Mild neutropaenia is common in Graves disease even prior to treatment. Pre therapy blood counts are therefore very useful and anti thyroid drugs can usually be safely given with monitoring in patients with pre treatment neutrophil counts between 1-1.5x10(9).
Normal ranges for neutrophil counts vary across different racial groups, with lower levels seen in Afro-Caribean patients.