Natpara

Natpara injection is used to treat hypocalcemia (low levels of calcium in the blood) in people who also have low levels of parathyroid hormone (hypoparathyroidism). Natpara injection is used after calcium and vitamin D alone have been tried without success.

Natpara is a manmade form of parathyroid hormone that occurs naturally in the body.

Natpara is available only under a special program (REMS) due to the potential risk of osteosarcoma. Patients must be registered in the program and understand the risks and benefits of this medicine. Only certified healthcare providers can prescribe, and only certified pharmacies can dispense Natpara.

Global manufacturing of Natpara has been discontinued and the U.S. Special Use Program for Natpara closed on December 31, 2025. Natpara alternative products are available for hypoparathyroidism, including Yorvipath (palopegteriparatide).

Take Natpara exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Natpara is injected under the skin. A healthcare provider may teach you how to properly use the medication by yourself.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you don't understand all instructions.

Use only the cartridges and injection pen provided with the medicine. Do not use a syringe to inject Natpara.

Do not shake the cartridge or you may ruin the medicine. Prepare an injection only when you are ready to give it. Do not use if the medicine has changed colors. Call your pharmacist for new medicine.

You will need frequent medical tests while using this medicine and for a short time after your last dose.

Do not change your dose or stop using Natpara without your doctor's advice. You could have dangerously low calcium levels if you stop using this medicine suddenly.

Store in the refrigerator, do not freeze. Protect from heat and light.

Each Natpara cartridge contains enough medicine for 14 separate injections. Throw the cartridge away after 14 uses, even if there is still medicine left inside.

Do not throw away the injection pen. It can be used for up to 2 years if you change the cartridge every 14 days.

Natpara has a black box warning for its potential risk of osteosarcoma. In animal studies, parathyroid hormone caused a malignant bone tumor (osteosarcoma). However, it is not known whether these effects would occur in humans. It should only be used in patients who cannot be well-controlled on calcium and active forms of vitamin D and for whom the potential benefits are considered to outweigh the potential risk. Natpara should not be used in patients who are at increased baseline risk for osteosarcoma (including those with Paget’s disease of bone or unexplained elevations of alkaline phosphatase, pediatric and young adult patients with open epiphyses, patients with hereditary disorders predisposing to osteosarcoma, or patients with a history of prior external beam or implant radiation therapy involving the skeleton),

Other warnings are:

• High blood calcium (hypercalcemia). This medicine can cause some people to have a higher blood calcium level than normal. Your healthcare provider should check your blood calcium before you start and during your treatment. Tell your healthcare provider if you have nausea, vomiting, or constipation, lack or energy, or muscle weakness. These may be signs that you have too much calcium in your blood.
• Low blood calcium (hypocalcemia). People who stop using or miss a dose of Natapara may have an increased risk of severe low blood calcium levels. Tell your doctor if you have numbness or tingling around your mouth or in your fingers and toes, muscle twitching in your face, cramps in your hands and feet, mood changes, or problems with thinking or memory. After you stop using Natpara, you may have low calcium levels.

You should not use Natpara if you are allergic to parathyroid hormone.

In animal studies, parathyroid hormone caused bone cancer. However, it is not known whether these effects would occur in humans. Ask your doctor about your risk.

To make sure Natpara is safe for you, tell your doctor if you have ever had:

• high levels of calcium in your blood;
• high levels of alkaline phosphatase in your blood;
• bone cancer;
• Paget's disease or other bone disorders; or
• radiation treatment.

Pregnancy

Tell your doctor if you are pregnant or plan to become pregnant. It is not known whether parathyroid hormone will harm an unborn baby.

Having hypocalcemia during pregnancy may increase the risk of miscarriage, premature birth, hypocalcemia in the baby, or eclampsia (dangerously high blood pressure that can lead to medical problems in both mother and baby). The benefit of treating hypocalcemia with Natpara may outweigh any risks to the baby.

Breastfeeding

You should not breastfeed while using this medicine. If you do breastfeed, tell your doctor if you notice symptoms in the nursing baby such as fussiness, weakness, stomach pain, poor feeding, vomiting, weight loss, constipation, more wet diapers than usual, muscle spasms, or tremors.

Natpara is not approved for use by anyone younger than 18 years old, or by anyone whose bones are still growing.

Common Natpara side effects

Common Natpara side effects may include:

• tingling, burning, or prickly feeling in your skin 31%
• Low blood calcium levels, hypocalcemia 27%
• Headache 25%
• High blood calcium levels 19%
• Nausea 18%
• Decreased sensitivity or numbness 14%
• Diarrhea 12%
• Vomiting 12%
• Joint pain 11%
• High urine calcium levels, hypercalciuria 11%
• Pain in extremities 10%

These common side effects occurred in 10% or more of patients on Natpara in the Phase 3 study, known as REPLACE (NCT00732615).

Serious Natpara side effects

Get emergency medical help if you have signs of an allergic reaction to Natpara: hives, itching; fast heartbeats, feeling light-headed, difficult breathing; swelling of your face, lips, tongue, or throat.

Natpara may cause other side effects, call your doctor at once if you have:

• new or unusual pain that is ongoing;
• swelling or tender lumps under your skin;
• a seizure; or
• high calcium levels - nausea, vomiting, constipation, increased thirst or urination, muscle weakness, bone pain, confusion, lack of energy, or tired feeling.

After you stop using this medicine, you may have low calcium levels. Tell your doctor if you have numbness or tingling around your mouth or in your fingers and toes, muscle twitching in your face, cramps in your hands and feet, mood changes, or problems with thinking or memory.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Usual Adult Natpara Dose for Hypocalcemia:

Before starting therapy:

• Confirm 25-hydroxyvitamin D stores are sufficient; if not, correct insufficiency per standard of care
• Confirm serum calcium is above 7.5 mg/dL

Initial dose:

• 50 mcg subcutaneously once a day

For patients using active forms of vitamin D:

• Decrease active vitamin D dose by 50% if serum calcium is above 7.5 mg/dL
• Maintain calcium supplement doses in those using calcium supplements
• Measure serum calcium concentration within 3 to 7 days
• Adjust active vitamin D dose or calcium supplement dose, or both based on serum calcium value and clinical assessment (see dosage adjustment section)
• ADJUST dose in increments of 25 mcg every 4 weeks if serum calcium cannot be maintained above 8 mg/dL without an active form of vitamin D and/or calcium supplementation

Maintenance dose:

• 25 to 100 mcg subcutaneously once a day

Comments:

• Dose should be individualized based on total serum calcium (albumin-corrected) and 24-hour urinary calcium excretion; maintenance dose is the minimum dose required to achieve serum calcium within the lower half of the normal range without the need for active forms of vitamin D and with calcium supplementation sufficient to meet the patient's daily requirements.
• With each dose change, monitor clinical response and serum calcium; adjust active vitamin D and calcium supplementation as needed (see dosage adjustment section).
• Due to potential risk of osteosarcoma, use should be reserved for those who cannot be well-controlled on calcium supplements and active forms of vitamin D alone.

Use the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not use two doses at one time.

Ask your doctor if you need to take extra calcium on the day you miss a dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Follow your doctor's instructions about any restrictions on food or beverages, especially if you drink milk or eat dairy products (cheese, yogurt, sour cream) or other foods high in calcium.

Tell your doctor about all your other medicines, especially:

• alendronate (Fosamax);
• digoxin; or
• vitamin or mineral supplements that contain calcium or vitamin D.

This list is not complete. Other drugs may interact with parathyroid hormone, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.