Zemplar capsules and injection contain the active ingredient paricalcitol, which is a type of medicine called a vitamin D analogue. It is used to treat overactivity of the parathyroid glands in people with chronic kidney failure.

How does it work?

  • Zemplar capsules and injection contain the active ingredient paricalcitol, which is a type of medicine called a vitamin D analogue. It is used to treat overactivity of the parathyroid glands in people with chronic kidney failure.
  • The parathyroid glands are found on the side of and behind the thyroid gland in the neck. These glands produce parathyroid hormone, which is involved in the metabolism of calcium and phosphorous in the body. Parathyroid hormone is produced in response to low levels of calcium in the blood. It causes calcium to be reabsorbed from bone in order to increase the level in the blood.
  • In chronic kidney failure the parathyroid glands can become overactive. This is because in kidney failure the level of calcium in the blood can fall too low.
  • The level of calcium in the blood is closely related to the activity of vitamin D in the body.
The kidneys normally convert vitamin D into an active form called calcitriol, and this helps control the absorption of calcium from the gut and its turnover in bone. However, in chronic kidney failure the kidneys are less effective at converting vitamin D into calcitriol. As a result, less calcium is absorbed from the gut, which causes the level of calcium in the blood to drop. The parathyroid glands produce more parathyroid hormone in response to this, causing more calcium to be reabsorbed from bone. This can weaken the bone and result in a condition called renal osteodystrophy.
  • Paricalcitol is a synthetic form of calcitriol. It works by binding to two specific receptors on the parathyroid glands, known as vitamin D receptors and calcium sensing receptors. By binding to these two receptors paricalcitol reduces the production and release of parathyroid hormone from the parathyroid glands. This helps to control levels of calcium and phosphate in the body and plays an important part in the regulation of bone mineralisation in people with chronic kidney failure.
  • Zemplar is only used in people with chronic renal failure who are on dialysis. The medicine is not removed by dialysis.
  • Use with caution in

    • Elderly people.
    • Severely decreased liver function.
    • People taking digoxin.

    Not to be used in

    • People with high levels of calcium in the blood (hypercalcaemia).
    • People with too much vitamin D in the body (vitamin D toxicity).
    • This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

    If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

    Pregnancy and breastfeeding

    • The safety of this medicine for use during pregnancy has not been established, however there is potential that it could be harmful to a developing baby. It should not be used during pregnancy unless considered essential by your doctor. Seek medical advice.
    • It is not known if this medicine passes into breast milk, however if it does it could cause the level of calcium in the nursing infant’s blood to rise too high. It should be used with caution in nursing mothers, and only if the benefits to the mother outweigh any risks to the nursing infant. Seek medical advice from your doctor.
    • If used in pregnancy or breastfeeding it should also be taken into account that this medicine contains small amounts of alcohol.

    Side effects


    • Rash or itching.
    • High or low blood calcium level (hypercalcaemia or hypocalcaemia).
    • High blood phosphate content (hyperphosphataemia).
    • Underactivity of the parathyroid glands.
    • Taste changes.
    • Headache.


    • Dizziness.
    • Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting, indigestion, abdominal pain, dry mouth, rectal bleeding.
    • Low red blood cell count (anaemia).
    • Decrease in the number of white blood cells in the blood (leucopenia).
    • Increase in bleeding time.
    • Abnormal heartbeats.
    • Swollen ankles (peripheral oedema).
    • Decreased appetite, weight loss.
    • Agitation, nervousness, confusion.
    • Changes in sensation, eg tingling or numbness.
    • Difficulty sleeping (insomnia).
    • Shortness of breath (dyspnoea).
    • Pain in muscles or joints, twitching.

    The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

    For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

    How can this medicine affect other medicines?

    Paricalcitol can cause the blood level of calcium to increase; in people taking digoxin this can lead to an increased risk of digoxin-related side effects.

    There may be an increased chance of the level of calcium in your blood rising too high if you take the following medicines in combination with paricalcitol:

    • calcium containing preparations, such as antacids, calcium supplements or calcium-based phosphate binders
    • phosphate containing preparations (should not be taken with this medicine)
    • thiazide diuretics such as bendroflumethiazide
    • vitamin D supplements (should not be taken with this medicine).

    If you are taking a calcium-based phosphate binder in combination with paricalcitol your doctor may need to reduce your dose if the level of calcium in your blood rises too high.

    Antacids or phosphate binders containing aluminium or magnesium should not be taken in combination with paricalcitol, as these may lead to increased blood levels of aluminium or magnesium.

    Ketoconazole, an antifungal medicine, can decrease the breakdown of paricalcitol in the body. As this may increase the amount of paricalcitol in the blood, your doctor may want to perform extra blood tests if you are taking ketoconazole with paricalcitol.