After changes in dose of levothyroxine, thyroid function tests (request TSH and FT4 and state patient is on levothyroxine) should normally be repeated after 8 weeks to allow steady state to be achieved. Once stable, check thyroid stimulating hormone (TSH) every 12 months and adjust the dose to normalise the TSH. The total daily dose can usually be administered as a single dose taken at least one hour apart from food and other medicines. For further guidance refer to www.british-thyroid-association.org.

LEVOTHYROXINE

Therapy notes

MHRA alert: Levothyroxine: new prescribing advice for patients who experience symptoms on switching between different levothyroxine products (May 2021) (www.gov.uk).
MHRA alert: Ritonavir-containing products: reports of interaction with levothyroxine leading to reduced thyroxine levels (October 2018) (www.gov.uk).

  • If a liquid levothyroxine preparation is required for patients with swallowing difficulties, crush tablets in 10 to 15mL water to make a suspension and take immediately washed down with some more liquid. The generic tablets from Concordia International and Actavis UK Ltd include this advice within their marketing authorisation (SPC). For specific advice for administration via an enteral feeding tube, refer to your pharmacist.

Formulation and dosage details

Formulation:

Tablets 25 micrograms, 50 micrograms, 75 micrograms, 100 micrograms

Dosage:

Initially 50 to 100 micrograms daily, adjusted in steps of 25 to 50 micrograms every 6 to 8 weeks until normal metabolism maintained (usually 100 to 200 micrograms daily). Older people or cardiac disease, initially, 25 to 50 micrograms daily.

Formulation and dosage details

Formulation:

Oral solution 100 micrograms/5mL

Dosage:

Initially 50 to 100 micrograms daily, adjusted in steps of 25 to 50 micrograms every 6 to 8 weeks until normal metabolism maintained (usually 100 to 200 micrograms daily). Older people or cardiac disease, initially, 25 to 50 micrograms daily.

LIOTHYRONINE

Therapy notes

Formulation and dosage details

Formulation:

Tablets 20 micrograms (s)

Dosage:

Short-term use only in thyroid cancer patients post-thyroidectomy/pre-radio-iodine therapy or iodine uptake scan, 20 micrograms three times daily.

Formulation and dosage details

Formulation:

Injection 20 micrograms (specialist use only)

Dosage:

By slow intravenous injection, hypothyroid coma, 5 to 20 micrograms repeated every 12 hours or as often as every 4 hours if necessary; alternatively 50 micrograms initially then 25 micrograms every 8 hours reducing to 25 micrograms twice daily.

Editorial Information

Document Id: F199