7311289
Description
Flashcards by Andrew Street, updated more than 1 year ago
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Created by Andrew Street
about 8 years ago
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| Question | Answer |
| Give eg's of & indications for thyroid hormones. | • eg's: levothyroxine, liothyronine Common indications: • Primary hypothyroidism • Hypothyroidism secondary to hypopituitarism |
| MOA of thyroid hormones. | The thyroid gland produces thyroxine (T4), which is converted to the more active triiodothyronine (T3) in target tissues. Thyroid hormones regulate metabolism & growth. Deficiency of these hormones causes hypothyroidism, with clinical features including lethargy, weight gain, constipation & slowing of mental processes. Hypothyroidism is Rx'd by long-term replacement of thyroid hormones, most usually as levothyroxine (synthetic T4). Liothyronine (synthetic T3) has a shorter half-life & quicker onset (a few hours) & offset (24–48 hrs) of action than levothyroxine. It is therefore reserved for emergency Rx of severe or acute hypothyroidism. |
| SE's of thyroid hormones. | • GI - diarrhoea, vomiting, weight loss • Cardiac - palpitations, arrhythmias, angina • Neurological - tremor, restlessness, insomnia |
| CI's, cautions, & important interactions of thyroid hormones. | CI's: • None Cautions: • Coronary artery DS - replacement should be started cautiously at a low dose & with careful monitoring • Hypopituitarism - corticosteroid Rx must be initiated before thyroid hormone replacement to avoid precipitating an Addisonian crisis Important interactions: As GI absorption of levothyroxine is reduced by antacids, calcium or iron salts, administration of these drugs needs to be separated by about 4 hrs. An ^in levothyroxine dose may be required in pt's taking cytochrome P450 inducers, e.g. phenytoin, carbamazepine. Levothyroxine-induced changes in metabolism can ^insulin or oral hypoglycaemic requirements in DM & enhance the effects of warfarin. |
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