Reviewed on 7/6/2022

What Is Voxelotor and How Does It Work?

Voxelotor is a prescription medication used to treat the symptoms of sickle cell disease in adults and children 12 years of age and older. 

  • Voxelotor is available under the following different brand names: Oxbryta

What Are Dosages of Voxelotor?

Adult and pediatric dosage


  • 500 mg

Tablet for oral suspension

  • 300 mg

Sickle Cell Disease

Adult dosage

  • 1500 mg orally once a day

Pediatric dosage

  • Children below 4 years: 
  • Safety and efficacy not established
  • Select appropriate product (tablets or tablets for oral suspension) based on the patient’s ability to swallow tablets and the patient weight
  • May take with or without hydroxyurea
  • Children above12 years
  • 1500 mg orally once a day
  • Children 4-11 years
  • Above 40 kg: 1500 mg orally once a day
  • 20 to below 40 kg: 900 mg orally once a day
  • 10 to below 20 kg: 600 mg orally once a day

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Are Side Effects Associated with Using Voxelotor?

Common side effects of Voxelotor include:

  • headache
  • diarrhea
  • stomach (abdominal) pain
  • nausea
  • tiredness
  • rash
  • fever

Serious side effects of Voxelotor include:

  • rash
  • hives
  • shortness of breath
  • swelling of the face

Rare side effects of Voxelotor include:

  • none

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheartedness, or passing out.
This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Voxelotor?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Voxelotor has severe interactions with the following drug:
    • lonafarnib
  • Voxelotor has serious interactions with at least 329 other drugs.
  • Voxelotor has moderate interactions with the following drugs:
  • Voxelotor has minor interactions with no other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions or concerns.

What Are Warnings and Precautions for Voxelotor?


  • Hypersensitivity: clinical manifestations may include generalized rash, urticaria, mild shortness of breath, mild facial swelling, and eosinophilia 

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Voxelotor?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Voxelotor?”


  • Serious hypersensitivity reactions have occurred in below 1 % of patients treated
  • Voxelotor may interfere with laboratory measurement of Hb subtypes (HbA, HbS, and HbF) by high-performance liquid chromatography (HPLC)
  • Drug interaction overview
    • Strong or moderate CYP3A4 inducers
    • Avoid coadministration with strong or moderate CYP3A4 inducers
    • Increase voxelotor dose if unable to avoid
  • Effect of voxelotor on other drugs
    • Voxelotor increased the systemic exposure of midazolam (a sensitive CYP3A4 substrate)
    • Avoid co-administration with sensitive CYP3A4 substrates with a narrow therapeutic index
    • Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid

Pregnancy & Lactation

  • Data are not available regarding use in pregnant women to evaluate for drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes
  • Clinical considerations
    • Women with sickle cell disease have an increased risk of adverse pregnancy outcomes for the mother and the fetus
    • Pregnant women are at greater risk for vasoocclusive crises, pre-eclampsia, eclampsia, and maternal mortality
    • For the fetus, there is an increased risk for intrauterine growth restriction, preterm delivery, low birth weight, and perinatal mortality
  • Lactation
    • Data are not available on the presence of voxelotor in human milk, effects on the breastfed child, or effects on milk production
    • Voxelotor was detected in milk in lactating rats; plasma concentrations of voxelotor in pregnant rats were higher than the concentration in milk
    • Advise women not to breastfeed during treatment and for at least 2 weeks after the last dose

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