Felis ISSN 2398-2950

Levothyroxine

Introduction

Name

Levothyroxine

Class of drug

  • Synthetic hormone.

Uses

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Indications

  • Used to treat hypothyroidism   Hypothyroidism  .
  • A synthetically-prepared hormone.

Administration

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Pharmocokinetics

Precautions

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Interactions

with other drugs

Catecholamines
(epinephrine, norepinephrine)
  • Effects are enhanced by thyroxine.

Sympathomimetics

  • Effects are enhanced by thyroxine.

Warfarin

  • Potentiate the anticoagulant effects of warfarin by increasing the catabolism of vitamin K-dependent clotting factors.

Insulin

  • Diabetic patients may have altered insulin requirements - monitor carefully during the initiation of therapy.

Estrogens

  • May increase thyroid requirements by increasing TBg.

Digoxin, digitoxin

  • The therapeutic effect may be reduced by thyroid hormones.

Ketamine

  • Increased risk of tachycardia and hypertension.

with diagnostic tests

  • Many drugs (in humans) may have effects on thyroid function tests including anabolic steroids, antithyroid drugs, barbiturates, corticosteroids, diazepam, fluorouracil, heparin, insulin, mitotane (op-DDD), nitroprusside, estrogens, phenylbutazone, phenytoin, propranolol, salicylates and thiazides.

Adverse Reactions

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Further Reading

Publications

Other sources of information

  • Based onSmall Animal Formulary.Tennant, Bryn (1999) 3rd edn. Cheltenham: BSAVA.

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