Meds and you

Updated 11 February 2013

Levothyroxine

Levothyroxine is a synthetic thyroid hormone, and is the medication of choice when treating a person with an underactive thyroid (hypothyroidism).

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Levothyroxine (also known as thyroxine) is the active ingredient of Eltroxin. It is also one of multiple active ingredients found in Diotroxin.

General information

Levothyroxine is a synthetic thyroid hormone, and is the medication of choice when treating a person with an underactive thyroid (hypothyroidism) - a condition in which the thyroid gland produces an insufficient amount of thyroid hormone. Symptoms of the resulting lowered metabolism include weight gain, a slow heart rate, constipation, dry skin, sensitivity to the cold, dry and brittle hair and nails and, in some cases, fluid accumulation and retention.

This medication may also be used to treat patients with an enlarged thyroid gland (goitre) or to treat certain types of thyroid cancer.

At the start of treatment your heart may beat more rapidly as your metabolism increases. If you have heart disease, it may cause angina - chest pain due to lack of oxygen to the heart muscle - or even trigger a heart attack. Your doctor may request regular blood tests during the early stages of treatment to measure the levels of levothyroxine in your body.

Levothyroxine does not cure hypothyroidism, but keeps it under control. To be effective, it has to be taken on a daily basis, often for life.

Treatment with this medication needs to be introduced gradually, and increased slowly, to prevent adverse effects.

How does Levothyroxine work?

Levothyroxine works by substituting and increasing the level of thyroid hormone in the human body.

Fast facts

Drug schedule: Schedule 3

Available as: Tablets

What does it do? Levothyroxine increase the level of thyroid hormone in the body

Overdose risk: Medium

Dependence risk: Low

Available as a generic ? No

Available on prescription only? Yes

User information

Onset of effect: It may take a few weeks for the full benefit to be achieved.

Duration of action: Up to 21 days.

Dietary advice: This medication should be taken on an empty stomach.

Stopping: Do not discontinue treatment without consulting you prescriber; Symptoms may recur.

Prolonged use: Prolonged used is common and few problems are expected. Your doctor may request regular blood tests to measure the levels of levothyroxine in your body and your thyroid function.

Special precautions

Alert your doctor before using this drug if:

  • you have a heart disease,
  • you have diabetes,
  • you have an overactive thyroid gland,
  • you have high blood pressure, or
  • you are taking any other medication.

Pregnancy: This drug is possibly safe to use. You should, however, consult your doctor prior to use.

Breastfeeding: Avoid. This medication is passed through breast milk and may affect your baby adversely. Consult your doctor before use.

Porphyria: This medication is safe to use.

Infants and children: A reduced dose is needed.

Elderly: Caution is advised in the elderly and dosage adjustment may be needed.

Driving and hazardous work: No special precautions need be taken.

Alcohol: Avoid concomitant use.

Possible side effects

Side effect

Frequency

Consult your doctor

Common

Rare

Only if severe

In all cases

Diarrhoea

x

x

Palpitations

x

x

Chest pain

x

x

Flushing

x

x

Sweating

x

x

Muscle cramps

x

x

Weight loss

x

x

Anxiety

x

x

Agitation

x

x

Change in appetite

x

x

Interactions

Drug interactions

Amiodarone

Thyroid activity may be affected and dose of levothyroxine may need to be adjusted

Warfarin

Increased risk of bleeding

Drugs used for treating epilepsy

Reduced effect of levothyroxine

Propranolol

Reduced effect of propranolol

Cholestyramine

Reduced effect of levothyroxine

Oral antidiabetic drugs

Possible reduced effect of antidiabetic drugs; dose needs adjustment

Phenylbutazone

May affect levothyroxine blood lest results

Rifampicin

Reduced effect of levothyroxine

Sucralfate

Reduced effect of levothyroxine

Disease interactions

Consult your doctor before using this drug if you have a heart disease, diabetes, an overactive thyroid gland or if you have high blood pressure.

Overdose action

A small overdose is no cause for concern. In case of intentional large overdose, seek emergency medical attention. Symptoms may include a rapid heartbeat, palpitations, chest pain and shortness of breath.

Recommended dosage

Adults: 50 - 150 mcg daily with a maximum daily dose of

200 mcg.

Children: Dosage should be determined by a paediatrician.

This material is not intended to substitute medical advice, but is for informational purposes only. Please consult a physician for specific treatment and recommendations.

 

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