Crysvita

Crysvita is a prescription medication used to treat patients 1 year of age or older with X-linked hypophosphatemia (XLH), an inherited disorder of low phosphorus levels in the blood.

Crysvita belongs to a group of drugs called anti-human fibroblast growth factor 23 (FGF23). This is a group of drugs that attaches to and stops the activity of FGF23, a protein responsible for phosphorus concentration in the blood.

This medication comes in single dose vials and is to be given directly under the skin (subcutaneously) by a healthcare provider once every 2 weeks for children and every 4 weeks for adults.

Common side effects include headache, decreased vitamin D levels, and vomiting. Crysvita can also cause dizziness. Do not drive or operate heavy machinery until you know how Crysvita affects you.

Crysvita is a prescription medication used to treat patients of 1 year of age or older with X-linked hypophosphatemia (XLH), an inherited disorder characterized by low phosphorus levels in the blood. 

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with Crysvita. See the “Crysvita Precautions” section.

• The most common adverse reactions that were seen in children with XLH are:
  • Headache
  • Injection site reaction
  • Vomiting
  • Fever
  • Pain in arms and legs
  • Decreased vitamin D levels
  • Rash
  • Toothache
  • Muscle pain
  • Tooth infection
  • Dizziness

• The most common adverse reactions that were seen in adults with XLH are:
  • Back pain
  • Headache
  • Tooth infection
  • Restless leg syndrome
  • Decreased vitamin D levels
  • Dizziness
  • Constipation
  • Phosphorus levels increased in the blood
• Narrowing of the spaces within the spine is common in adults with XLH and pressure on the spinal cord has been reported in adults taking Crysvita. It is not known if taking Crysvita worsens the narrowing of the spaces within the spine or the pressure on the spinal cord.

This is not a complete list of Crysvita side effects. Ask your doctor or pharmacist for more information.

Tell your doctor if you have any side effects that bother you or that do not go away.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

No drug interactions have been studied by the manufacturer. However, you should tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements. Not all drug interactions are known or reported and new drug interactions are continually being reported.

Serious side effects have been reported with Crysvita including the following:

• Hypersensitivity (severe allergic reaction). Tell your healthcare provider about any signs or symptoms of hypersensitivity, which include the following:

  • chest pain
  • swelling of the face, eyes, lips, tongue, arms, or legs
  • difficulty breathing or swallowing
  • rash
• High blood phosphorus levels and risk of calcium stone buildup in kidneys. Increase in blood phosphorus concentration above normal levels can result in calcium stone formation in the kidneys. This may require a dose reduction.
• Injection site reactions. Local injection site reactions have been reported in patients taking Crysvita. Discontinue Crysvita if you experience severe injection site reaction and receive immediate medical treatment:
  • redness, itching, or sensitivity to pain
  • pain, swelling, or signs of inflammation
  • skin sore/wound or any new skin abonormality at injection site

Crysvita can cause drowsiness. Do not drive or operate heavy machinery until you know how Crysvita affects you.

Do not take Crysvita if you:

• are allergic to Crysvita or to any of its ingredients
• take oral phosphate and active vitamin D supplements
• have normal or increased blood phosphorus levels
• have severe renal impairment or end stage renal disease

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of Crysvita, there are no specific foods that you must exclude from your diet when receiving this medication.

Before taking Crysvita, tell your doctor about all of your medical conditions, including if you:

• have kidney problems
• have phosphorus levels above the normal range
• are pregnant, think you may be pregnant, or plan to become pregnant. There is not enough experience to know if Crysvita may harm your unborn baby. Report pregnancies to the Ultragenyx Adverse Event reporting line at 1-888-756-8657.
• are breastfeeding or plan to breastfeed. There is not enough experience to know if Crysvita passes into your breast milk. Talk with your doctor about the best way to feed your baby while you receive Crysvita.

While taking Crysvita, tell your doctor if you experience:

• An allergic reaction such as rash or hives
• A rash, swelling, bruising or other reaction at the injection site
• New or worsening restless leg syndrome

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

There are no well-done studies that have been done in humans with Crysvita. In animal studies, pregnant animals were given this medication, and the babies did not show any medical issues related to this medication. An increase in late fetal loss, a shortened gestation period, and an increase in preterm birth incidences were observed at a a drug exposure that was 64 times higher in pregnant cynomolgus monkeys.

Tell your doctor if you are breastfeeding or plan to breastfeed.

It is not known if Crysvita crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using Crysvita.

Crysvita comes in single dose vials and is to be given directly under the skin (subcutaneously) by a healthcare provider once every two weeks for children and every 4 weeks for adults.

Injection sites should be rotated with each injection at different body areas (upper arms, upper thighs, buttocks, or abdomen). Avoid injecting into any areas with skin abnormalties. The maximum injection volume is 1.5 mL and should be split and injected at a different sites if more than 1.5 mL.  

Crysvita is a clear colorless to pale brown-yellow solution. Discard the solution if it is discolored, cloudy, or if it contains any particles. 

If you miss a dose, continue Crysvita as soon as possible by talking to your healthcare provider.

The dose your doctor recommends may be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking
• how you respond to this medication
• your weight
• your height
• your age
• your gender

Crysvita comes in a single dose vial with three different strengths of 10 mg/mL, 20 mg/mL, or 30 mg/mL.

Pediatric XLH: Starting dose regimen is 0.8 mg/kg of body weight rounded to the nearest 10 mg, administered every two weeks. The minimum starting dose is 10 mg up to a maximum dose of 90 mg. Dose may be increased up to approximately 2 mg/kg (maximum 90 mg), administered every two weeks to achieve normal serum phosphorus.

Adult XLH: Dose regimen is 1 mg/kg body weight rounded to the nearest 10 mg up to a maximum dose of 90 mg administered every four weeks.

If Crysvita is administered by a healthcare provider in a medical setting, it is unlikely that an overdose will occur. However, if overdose is suspected, seek emergency medical attention.

Crysvita vials must be stored in the original carton until the time of use under refrigerated conditions at 36°F to 46°F (2°C to 8°C). Keep Crysvita vial in the original carton to protect from light until time of use.

Do not freeze or shake Crysvita. 

Do not use Crysvita beyond the expiration date stamped on the carton.

Crysvita vials are single-dose only. Discard any unused product.