Interruption of oral thyroxine replacement therapy for hypothyroidism in adults
If interruption of oral thyroxine replacement therapy is required (eg for elective surgery) in a patient who is euthyroid on therapy, thyroxine can be safely withheld for up to 7 days.
Ideally, hypothyroidism should be adequately treated before proceeding with elective surgery. If delaying surgery is not feasible, ensure the surgeon and anaesthetist are aware that the patient is hypothyroid.
Restart oral therapy as soon as the patient can take oral fluids. If oral therapy is still not possible after 7 days, start parenteral levothyroxine or liothyronine. Use:
1 levothyroxine by slow intravenous injection, until oral therapy is tolerated1 hypothyroidism, nil oral intake levothyroxine
if usual oral dose is known: 75% of usual daily dose (to the nearest 25 micrograms), daily
if usual oral dose is not known: 1.2 micrograms/kg (to the nearest 25 micrograms), daily
OR
2 liothyronine 10 micrograms by slow intravenous injection, two or three times daily, until oral therapy is tolerated2. hypothyroidism, nil oral intake liothyronine