Itraconazole

Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2004.


What is itraconazole?

Itraconazole is an triazole medicine used to treat fungal infections.

What is itraconazole used for?

Itraconazole is effective against a broad spectrum of fungi including:

Itraconazole is sometimes used for inflammatory skin diseases such as atopic eczema, seborrhoeic dermatitis or psoriasis, if a fungus or yeast is thought to be contributing to the condition.

Itraconazole has recently been observed to slow the growth of basal cell carcinoma, and is occasionally used for this purpose off-label.[1,2]

How does itracoanzole work?

Itraconazole binds to the fungal p450 enzymes and stops the cells making ergosterol, the main component of the cell wall.

How is itraconazole taken?

In New Zealand, itraconazole is available as 100 mg capsules on prescription and a 10 mg/mL liquid preparation. A generic, Itrazole, is funded under some circumstances. Sporanox™, is the registered trademark for itraconazole preparations, copyright Janssen-Cilag. Sporanox oral liquid is subsidised on Special Authority application for children with immunodeficiency and relevant infections.

The medication is better absorbed orally when it is taken with a fatty meal or acidic drink (eg, orange juice). It is bound to proteins such as albumin in the circulating blood and becomes concentrated in fat cells and within skin and nails. It takes one to three days for half of the medication to be cleared from the blood stream. The rest is eliminated in faeces and urine after conversion by the liver into inactive compounds.

Skin concentrations may be 3–10-fold higher than those in the blood. It may persist in the skin for up to 4 weeks after the drug has been discontinued and in the nails for up to a year.

Dose regime for itraconazole

Various regimes for itraconazole have been found successful; typical doses are listed below. Courses can be repeated and the medication can be continued for months if necessary.

The dose of itraconazole in children is usually 5 mg per kg body weight per day to maximum 200 mg per day, but is reserved for exceptional circumstances.

Side effects of itraconazole

Itraconazole appears to be a relatively safe drug. Side effects, usually minor, are more likely during a prolonged course of treatment.

  • Nausea and vomiting (5%)
  • Constipation
  • Headache
  • Dizziness
  • Abnormal liver function tests (up to 5% for those on long term therapy, 2% for pulse therapy); significant liver disease is rare
  • Allergic skin rash including urticaria
  • Endocrine effects including enlarged breasts (in males) and adrenal suppression
  • Tingling in the fingers and toes (very rare)
  • Congestive heart failure: itraconazole should be used with caution in those with heart problems.

Itraconazole is best avoided in pregnancy. Although only excreted in tiny amounts from breast milk, it should only be taken by a breast-feeding mother if essential.

Drug interactions with itraconazole

Itraconazole has important interactions with other medications.

As itraconazole needs acid for its absorption, antacids, H2 antagonists (cimetidine, famotidine, ranitidine) and omeprazole should not be taken for 2 hours after itraconazole.

Itraconazole is a P-glycoprotein inhibitor and increases the concentration of some drugs.

These drugs should not be taken by those on itraconazole:

  • HMG Co-A reductase inhibitors (atorvastatin, lovastatin, simvastatin); fluvastatin, rosuvastatin and pravastatin are acceptable alternatives. Toxicity due to the combination of drugs results in muscle pain and weakness, which may be serious.
  • Cisapride
  • Midazolam, triazolam
  • The antihistamines astemizole (Hismanal®) and terfenadine (Teldane®); these are no longer available in New Zealand.

Itraconazole may increase the risk of bleeding from anticoagulants such as warfarin or dabigatran.

The dose of these drugs should be reduced:

The dose of these drugs may need reducing if side effects arise:

  • Quinidine
  • Calcium channel blockers
  • Antidiabetic sulphonylurea medication (tolbutamide, glibenclamide, gliclazide, glipizide)

The following drugs decrease the concentration of itraconazole:

Itraconazole is not thought to interact with the oral contraceptive pill.

New Zealand approved datasheets are the official source of information for these prescription medicines, including approved uses and risk information. Check the individual New Zealand datasheet on the Medsafe website.

 

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