While most patients take a daily dose, the long half-life of thyroxine lends itself to longer dosing intervals, such as alternate daily dosing. Once-weekly dosing is also possible although a slightly larger dose than seven times the normal daily dose may be required.The resulting mixture should be used immediately and any remainder discarded. 2 Breast milk contains only 2030 of the calcium concentration of cows milk, making the likelihood of decreased thyroxine bioavailability less likely.
The expiry date should be emphasised to the patient to ensure they do not continue taking a thyroxine preparation that may be waning in potency. However, stock with a shelf-life of 18 months will soon be available.FREE T4 1.10, normal range 0.71 - 1.81. FREE T3 3.5, normal range 2.3 - 4.2. In mid-May 2010, I had some blood tests, and here are the results: TSH 0.636, normal range 0.350 - 5.500.
The two Australian brands are marketed by Sigma and one of its subsidiaries. They are identical products so patients can swap them safely, but this assumption should not be extended to overseas brands.Drug interactions Most drug interactions are seen during shifts to and from the euthyroid state and rarely have any clinical significance during periods of thyroid stability. The hyperthyroid state increases clearance of some hepatically cleared drugs, notably propranolol, metoprolol and theophylline.
It is essential that prescribers and pharmacists convey this information to patients in order that therapeutic efficacy may be maximised. References 1. AHFS drug handbook. 2nd ed. Bethesda (MD American Society of Health-System Pharmacists, Lippincott Williams Wilkins; 2003.Treatment of hypothyroidism with once weekly thyroxine. J Clin Endocrinol Metab 1997;. 4. Australian Medicines Handbook 2004. Adelaide: Australian Medicines Handbook Pty Ltd; 2004. Further reading Toft AD. Clinical practice. Subclinical hyperthyroidism.
1 The expiry date for Australian manufactured thyroxine tablets is one year from the date of manufacture. There are 200 tablets in a bottle, so it is possible that patients on half tablet doses will not finish the bottle before the stock expires.So my latest blood work revealed that I need a dose change and that I'm insulin resistant. I am now taking 200mg of levothyroxine for hypothyroidism and 40mg of atorvastatin for cholesterol and fatty liver.
N Engl J Med 2001;. Conflict of interest: none declared Self-test questions The following statements are either true or false ( click here for the answers ) 1. The dose of thyroxine should be decreased in patients with renal failure.I started taking levothyroxine, and the first dosage was 50 mcg. The dosages increased gradually. In early March 2010, I started taking 137 mcg of levo. In mid-April 2010, I had some blood tests, and here are the results: TSH 1.016, normal range 0.350 - 5.500.
I also take fish oil, multivitamin, D3, allegra, and baby aspirin. My medical provider is focusing on my thyroid before tackling everything else. I should also mention that my mother has non alcoholic cirrhosis of the liver, diabetes, dementia, diverticulitis, and myopathy.Some substances bind the thyroxine, making it unavailable for diffusion across the gut wall. Concurrent administration with iron salts, antacids, calcium carbonate (including milk sucralfate, cholestyramine and soy-based formulas may therefore decrease absorption of thyroxine.
Stability. Thyroxine is stable in dry air, but unstable in the presence of light, heat and humidity. In some cases overseas, thyroxine tablets have been unstable even at room temperature, and storage temperatures of 8C to 15C were required to maintain potency.1, 2 Monitoring The dosage is adjusted according to thyroxine and thyroid stimulating hormone plasma concentrations, which should always be interpreted in conjunction with each other and the patients condition. 4 Monitoring is suggested at six-weekly intervals when starting therapy until the patient has stabilised, then six monthly thereafter, or earlier if symptoms suggestive of.
Nonetheless, if breast milk is used to deliver the thyroxine, it should be used consistently, in order to minimise any variation in absorption. Onset and duration of action. The half-life of thyroxine in euthyroidism is 67 days.In view of the long half-life, dose changes should only be made every 34 weeks. Despite undergoing both hepatic and renal clearance, there is no evidence that dose adjustment is required for patients with liver or kidney disease.
2. Thomas J, editor. Australian Prescription Products Guide 2003. 32nd ed. Hawthorn: Australian Pharmaceutical Publishing Company Limited; 2003. 3. Grebe SK, Cooke RR, Ford HC, Fagerstrom JN, Cordwell DP, Lever NA, et al.Gregory W. Roberts, Clinical Pharmacist, Repatriation General Hospital, Daw Park, South Australia. Summary Some of the pharmaceutical properties of thyroxine have important implications for the quality use of medicines. The stability of thyroxine tablets is limited and they may reach the expiry date before the bottle is finished.
In the USA, the Food and Drug Administration has determined that stability and potency problems with oral thyroxine preparations could potentially have adverse effects on health. It is therefore very important that thyroxine tablets should be kept in their original container and stored out of sunlight in a cool dry place.Antacids, iron salts, calcium carbonate (milk sucralfate, cholestyramine and soy-based formulas reduce the absorption of thyroxine. Conclusion There are significant stability, absorption and drug interaction issues surrounding the use of thyroxine.
This formulation will require refrigeration at all times. Absorption Thyroxine is variably absorbed from the gut following oral administration. It has a bioavailability of 4080. Absorption may decrease with age. 1, 2 The extent of thyroxine absorption is increased in the fasting state and is influenced by the content of the gastrointestinal tract.Administration should preferably be on an empty stomach and be consistent with respect to food and other drugs. The long half-life of thyroxine enables longer dosing intervals of up to a week if required.
This is reduced to 34 days in hyperthyroidism and prolonged to 910 days in hypothyroidism. Thyroxine has a full therapeutic effect 34 weeks after starting treatment and will continue to have a therapeutic action for 13 weeks after treatment stops.There are two brands of thyroxine available in Australia, each as 50 microgram, 100 microgram and 200 microgram tablets (pack size 200) with five repeats on the Pharmaceutical Benefits Scheme. Parenteral preparations of thyroid hormone have little use in Australia, outside of specialist centres.
2. Food increases the absorption of thyroxine tablets. Answers to self-test questions 1. False 2. False First published online.This regimen may be suitable for poorly compliant patients who require supervised dosing. 3 For patients, particularly children, who cannot swallow tablets, the tablets may be crushed in 1020 mL of water, breast milk or non-soybean formula.
The two Australian brands of thyroxine are identical and patients can swap brands safely, but this should not be assumed for overseas brands. Key words: hypothyroidism, hyperthyroidism, pharmacokinetics. Aust Prescr 2004; Introduction Thyroxine tablets are important in managing hypothyroidism, but treatment may be sub-optimal if they are used incorrectly.Patients who still decide to take their tablets with, rather than before, breakfast need to do this consistently, to avoid fluctuating thyroxine concentrations. Depending on the fibre and milk content of the meal, taking thyroxine with food may require a larger dose to maintain euthyroidism, because of the decreased bioavailability.
The tablets have pharmaceutical properties which can impair the patients management. Discussing the correct use and storage of the tablets is an important part of prescribing thyroxine. Availability Synthetic preparations of thyroxine contain the laevo isomer of thyroxine, usually as the sodium salt.FREE T4 1.
Administration Patients should be instructed to take thyroxine 3060 minutes before breakfast in order to maximise absorption. If this is too difficult or threatens compliance, the patient may try taking the thyroxine last thing at night on an empty stomach." Wilson's Syndrome This is a theory and treatment protocol pioneered by Dr. E. Denis Wilson. According to Dr. Wilson traditional medical theory regarding the thyroid only recognizes either a state of good health or a state of severe illness.