Atazanavir

Atazanavir - Dosage | Adverse Effects

Atazanavir is a well-known drug for the treatment of AIDS and belongs to a group of medicines called HIV protease inhibitors. It is used alone or in combination with "enhancers" or drugs that enhance its effect. It belongs to a relatively newer HIV medication and its main feature is that it does not cause an increase in cholesterol and triglyceride levels in the blood as earlier HIV drugs did.

In the USA, the drug has been approved as first choice drug for the treatment of AIDS in adult patients.

How it works is quite clear - it blocks an enzyme called HIV protease that is responsible for the maturation and replication of the HIV virus. Thus, the blockade of this enzyme causes the formation of non-infectious HIV virus.1

Precautions

Since this drug is a UGT1A12 inhibitor (UGT1A1 is the enzyme responsible for the metabolism of bilirubin), an increase in the level of bilirubin in the blood is inevitable. Increased levels of bilirubin causes a condition called hyperbilirubinemia. In some patients, inhibition of this enzyme is more pronounced which causes jaundice, while in other patients, the inhibition of UGT1A1 is less pronounced and causes no symptoms. It has been reported that the incidence of this adverse effect in patients taking Atazanavir is about 10%, while 1% of the patients had to stop treatment because of severe hyperbilirubinemia.3 Generally, hyperbilirubinemia and jaundice does not lead to the liver damage, but is aesthetically unacceptable for some patients, which is the main reason for them to stop taking this drug.

If you experience jaundice, tell your doctor about it, and he will decide whether treatment should be stopped or not.

Use of this drug is not recommended for the following patients:

  • Patients with liver impairment.
  • Patients suffering from hemophilia A (considering that HIV protease inhibitors are associated with increased risk of bleeding)4.
  • Patients with renal impairment (considering that Atazanavir is associated with an increased risk of developing acute and chronic renal disease)5. It is necessary to regularly monitor kidney function while you are on treatment with this medicine.
  • Patients with diabetes (Atazanavir can increase blood sugar levels, and should be used with caution in diabetics).6
  • Patients with arrhythmias (Atazanavir may cause changes in the heart rhythm which can be seen on an electrocardiogram as a prolonged QRS interval).7
  • Patients who have had a heart attack. There have been reported cases of arrhythmia and the occurrence of chest pain in patients taking this drug.8

Atazanavir, pregnancy and breastfeeding

FDA has classified this drug in group B, which means that animal studies have shown no adverse effects on the fetus.

FDA has approved the use of a combination of atazanavir / ritonavir (300 mg / 100 mg) in pregnant women.9

Atazanavir is not expected to cause adverse effects to a fetus.

You should not breastfeed while being treated with this drug. Use appropriate alternative baby milk formula available in the market.

Dosage

Atazanavir exists in the form of capsules.

The recommended dose is 300 mg of Atazanavir in combination with 100 mg ritonavir, once daily, after lunch.

If applied alone, then the usual dose is 400 mg of Atazanavir once daily.

300 mg of atazanavir can be also applied in combination with 150 mg of cobicistat.

Ritonavir and cobicistat are "enhancers" of atazanavir - enhancing its effect.

Interactions

Atazanavir inhibits CYP3A4, and interacts with many drugs. So far, about 3,000 interactions of this drug are known.

Below are listed some significant Atazanavir interactions.

Drugs that interact with Atazanavir Possible consequences of interaction
Antagonists of 5-HT3 receptors, such as: Dolasteron Heart problems (arrhythmia)
Loperamide, a drug used for the treatment of diarrhea Arrhythmias, fainting, shortness of breath, heart attack
Opioid analgesics, such as: Fentanyl, Oxycodone Bradycardia, loss of consciousness, shortness of breath and rapid breathing
Beta blockers (medicines used to treat heart disease), such as: Acebutolol, Timolol, Bisoprolol, Betaxolol Arrhythmia, cardiac arrest
Corticosteroids, such as: Prednisone, Fluticasone, Budesonide, Triamcinolone Loss of bone density - increased risk of bone fractures, acne, depression, increase in the level of glucose in the blood
Drugs used for the treatment of stomach and duodenal ulcers, such as: Ranitidine, Omeprazole, Esomeprazole, Pantoprazole Reduction of Atazanavir absorption and consequently a decrease in the concentration of Atazanavir in the blood and its effectiveness
Calcium antagonists (medicines used for treatment of heart diseases), such as: Verapamil, Diltiazem Increased risk of arrhythmias and serious heart problems

Tell your doctor about all the medicines you are taking because there is strong possibility that Atazanavir may change their effects.

Adverse effects

Adverse effects of the Atazanavir include:

  • Hyperbilirubinemia and consequently jaundice
  • Back pain
  • Insomnia
  • Trouble concentrating
  • Muscle weakness, especially in the feet and hands
  • Muscle stiffness
  • Headache
  • Stomach pain
  • Decreased appetite
  • Diarrhea or constipation
  • Fever
  • Shortness of breath and rapid breathing

Reference

  1. NCBI link 1
  2. Accessdata link 1
  3. NCBI link 2
  4. NCBI link 3
  5. NCBI link 4
  6. NCBI link 5
  7. NCBI link 6
  8. NCBI link 7
  9. Accessdata link 2