Home Medicines Calcitriol: effect, areas of application, side effects

Calcitriol: effect, areas of application, side effects

by Josephine Andrews
Published: Last Updated on 384 views

Calcitriol is the activated form of vitamin D and as such performs many functions in the body. The active ingredient therefore has a wide range of applications, from kidney disease and functional disorders of the parathyroid gland to psoriasis and severe forms of vitamin D deficiency. Here you can read everything you need to know about calcitriol: application, mode of action and possible interactions and side effects.

This is how calcitriol works

Calcitriol is the active form of vitamin D and is responsible for the regulation of the phosphate and calcium balance and the mineralization of the bones.

In contrast to all other vitamins, vitamin D is not essential, which means that the body does not necessarily have to get it from food, but can also produce it itself. A deficiency only occurs in the case of metabolic disorders or a lack of sunlight on the skin (the UV-B component in the light is particularly important here ).

Humans need sunlight to produce vitamin D. From a cholesterol derivative in the skin, the body produces vitamin D3 with the help of sunlight, but this is not yet an active vitamin. Vitamin D3 travels through the blood to the liver, where it is converted to calcidiol – the inactive storage form of vitamin D3. If necessary, this is converted into the active form calcitriol in the kidneys.

Calcitriol has many functions in the human body, above all – hence the name – it affects the calcium level in the blood: high calcitriol levels increase the blood levels of calcium.

This happens through an increased absorption of calcium from the intestine , an increased reabsorption of the mineral from the urine and its increased release from the bones. The latter can lead to bone loss. Indirectly, i.e. in interaction with other hormones, calcitriol works against bone loss.

Calcitriol also has a positive effect on the immune system. It improves the defense against infections and sometimes protects against autoimmune diseases (e.g. psoriasis and patchy hair loss ). A reduced incidence of certain types of cancer also seems to be based on this effect. Calcitriol also has an effect on the nervous system, muscles and blood pressure.

The advantage of calcitriol over cholecalciferol (=vitamin D3) is that it does not have to be activated by the body first. This means that people with severe liver or kidney dysfunction can also be treated successfully.

intake, degradation and excretion

After ingestion, the active ingredient is absorbed into the blood via the intestines, where it reaches its highest level after two to six hours. Since it is fat-soluble, it is transported in the blood by transport proteins.

Calcitriol is broken down in the kidneys and liver and excreted in the bile in the stool. Five to eight hours after taking it, his blood level has halved again.

When is calcitriol used?

Calcitriol is approved for the treatment of:

  • kidney-related bone formation disorders
  • Underactive parathyroid gland (hypoparathyroidism)
  • Vitamin D-resistant rickets (disorder of bone metabolism due to vitamin D deficiency )
  • Osteoporosis in patients with chronic renal dysfunction when other therapies fail or are not possible due to contraindications (contraindications).

In these cases, it is used internally, for example in the form of capsules or injections. External use (as a calcitriol ointment) is approved for the treatment of mild to moderately severe psoriasis .

In Switzerland, calcitriol is also approved for the treatment of postmenopausal osteoporosis (osteoporosis after menopause).

The duration of use depends on the type and severity of the disease. In the case of chronic diseases, the application is permanent.

This is how calcitriol is used

Calcitriol is usually taken in the form of soft capsules that contain the active ingredient dissolved in oil. Therapy is started at a low dose of 0.25 micrograms of calcitriol once a day. Depending on how the patient responds to the therapy and how the calcium blood level changes, the dose is increased very slowly.

Common dosages are between 0.25 and 1.0 micrograms of calcitriol per day. If less than 0.25 micrograms of calcitriol per day is sufficient, one soft capsule can also be taken every other day.

Low doses are taken once a day with breakfast, higher doses divided into two to three daily doses and also taken with meals with a glass of water.

For the external treatment of psoriasis, an ointment with three micrograms of calcitriol per gram of ointment is applied to the affected skin twice a day. No more than one third of the total surface area of ​​the body should be rubbed per application and the duration of the application should not exceed six weeks.

What are the side effects of calcitriol?

The side effects of treatment with calcitriol essentially correspond to a vitamin D overdose .

Increased calcium blood levels occur in more than every tenth patient, which is why attention should also be paid to daily calcium intake (from dairy products, etc.). Common side effects also include headaches, abdominal pain, nausea, skin rashes, and urinary tract infections.

Occasionally, treatment can decrease appetite, cause vomiting and increase blood creatinine levels.

When used as an ointment, side effects are usually limited to the skin and may manifest as itching, irritation, or redness.

What should be considered when taking Calcitriol?

Contraindications

Calcitriol must not be used in:

  • Hypersensitivity to the active substance or any of the other components of the drug
  • disease-related excess calcium in the blood (hypercalcaemia)
  • Suspected vitamin D overdose

Calcitriol ointment must not be applied to:

  • Hypersensitivity to the active ingredient or any of the other components of the ointment
  • concomitant use of drugs to regulate calcium balance
  • Hypercalcemia and calcium metabolism disorders
  • liver dysfunction
  • renal dysfunction

interactions

When a doctor prescribes calcitriol for a patient, they usually also provide certain dietary advice, particularly regarding the consumption of calcium-rich foods and drinks. Patients should strictly follow these instructions.

The simultaneous intake of water-reducing medicines (diuretics) can also increase the calcium level in the blood. Cardiac patients in particular who are being treated with digitalis glycosides (a heart medication) must avoid high calcium levels, as these can lead to serious cardiac arrhythmias.

Anti-inflammatory glucocorticoids (“cortisone”) inhibit the effect of calcitriol.

Certain active ingredients for lowering cholesterol (colestyramine, sevelamer) can prevent the absorption of calcitriol in the intestine and should, if necessary, be taken at a large time interval.

age restriction

If necessary, calcitriol can be given as early as infancy.

The safety and effectiveness of calcitriol capsules in children and adolescents have not been sufficiently studied to be able to give dosage recommendations.

For injection, data are limited in children under the age of nine or on dialysis. The attending doctor weighs the possible advantages against the disadvantages of the treatment and adjusts the dosage individually based on other blood values ​​and body weight.

The safety and effectiveness of calcitriol ointment for psoriasis in children and adolescents under the age of 18 have not been established.

pregnancy and breast feeding period

There are no results from controlled studies on the use of calcitriol during pregnancy and breastfeeding. So far, however, there is no evidence that calcitriol would have a harmful effect on the unborn child in pregnant women. However, the active ingredient should only be used in expectant mothers if the benefit outweighs the possible risk.

Vitamin D and its metabolites (including calcitriol) pass into breast milk. Therefore, the blood calcium levels of mother and infant should be closely monitored during lactation if the mother is being treated with calcitriol.

For topically applied calcitriol, the systemic (entering the systemic circulation) amount is extremely small. Nevertheless, the ointment should only be used after a medical benefit-risk assessment and on as small an area as possible.

How to get medication with calcitriol

Calcitriol as a capsule requires a prescription in Germany, Austria and Switzerland in any dosage and pack size. Preparations for injection or application to the skin (ointment) are only available in Germany and Switzerland, but not in Austria.

Since when is calcitriol known?

The discovery of vitamin D metabolism began as early as the 1920s. However, it was not until the 1970s that the activated form of the vitamin, calcitriol, could be decoded. The two research groups led by the American endocrinologist M. Holick and the biochemist A. Norman were in a neck-and-neck race.

In 1984, the first drug containing the active ingredient calcitriol was approved in Germany; there are now several generics.

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