Issues for Surgery
None – providing patient’s hyperthyroidism is well controlled (see Further Information).
Advice in the Perioperative period
Propylthiouracil may cause thrombocytopenia hence patients undergoing surgery should have their prothrombin time checked pre-operatively1.
A thyroid stimulating hormone (TSH) test should be included in pre-operative assessment to determine the adequacy of treatment and to ensure that thyroid therapy is optimised before surgery2.
Patients undergoing Thyroidectomy
Continue usual dose.
Interaction(s) with Common Anaesthetic Agents
None1, 3, 4, 5, 6, 7.
Interaction(s) with other Common Medicines used in the Perioperative Period
Carbimazole may inhibit the metabolism of erythromycin, leading to reduced clearance of erythromycin4 and possibly torsades de pointes in susceptible individuals5.
Carbimazole Important Safety Information3
Healthcare professionals should be alert to the potential for carbimazole-induced bone marrow suppression and the need to stop treatment promptly: -
Propylthiouracil Safety Information
Thyrotoxicosis and Thyroid Storm
Thyrotoxicosis is a condition that occurs due to excessive circulating thyroid hormones (it includes hyperthyroidism). Signs and symptoms include weight loss, heat intolerance and palpitations.
Thyroid storm is a life-threatening form of untreated or under-managed hyperthyroidism. It is characterised by high fever, fast and irregular heart rate, elevated blood pressure, vomiting, diarrhoea and agitation.
There is a potential risk of thyrotoxicosis or thyroid storm if antithyroid hormones are omitted perioperatively. However, the actual risk is dependent on the patient’s TFTs and the length of time they are omitted. It takes 4 – 6 weeks from being euthyroid to the patient becoming thyrotoxic once the antithryroid agents are stopped. The emergence of thyroid storm would be rare. If there are any concerns regarding the omission or continuation of antithyroid medication during the perioperative period, the patient’s Endocrinologist should be consulted.