Dihydrotachysterol-drug affecting calcium balance and its pharmacology.

                                                                    

DESCRIPTION :    

A vitamin D that can be regarded as a reduction product of vitamin D2. [PubChem]

CATEGORY :       

Bone Density Conservation Agents

Vitamins

Antithyroid Agents

Vitamin D

Antihypocalcemic Agents

Alimentary Tract and Metabolism

Vitamin D and Analogues

PHARMACODYNAMICS :

Dihydrotachysterol is hydroxylated in the liver to 25-hydroxydihydrotachysterol, which is the major circulating active form of the drug. It does not undergo further hydroxylation by the kidney and therefore is the analogue of 1, 25-dihydroxyvitamin D. Dihydrotachysterol is effective in the elevation of serum calcium by stimulating intestinal calcium absorption and mobilizing bone calcium in the absence of parathyroid hormone and of functioning renal tissue. Dihydrotachysterol also increases renal phosphate excretion.

MECHANISM OF ACTION :

Once hydroxylated to 25-hydroxydihydrotachysterol, the modified drug binds to the vitamin D receptor. The bound form of the vitamin D receptor serves as a transcriptional regulator of bone matrix proteins, inducing the expression of osteocalcin and suppressing synthesis of type I collagen. Vitamin D (when bound to the vitamin D receptor)stimulates the expression of a number of proteins involved in transporting calcium from the lumen of the intestine, across the epithelial cells and into blood. This stimulates intestinal calcium absorption and increases renal phosphate excretion. These are functions that are normally carried out by the parathyroid hormone.

PHARMACOKINETIC DATA :

Protein Binding : 99%

Toxicity :

Toxicity associated with dihydrotachysterol is similar to that seen with large doses of vitamin D.

DRUG- DRUG INTETRACTION :

               

Acenocoumarol  +Dihydrotachysterol :

Dihydrotachysterol may decrease the anticoagulant activities of Acenocoumarol.

Alfacalcidol + Dihydotachysterol  :

The risk or severity of adverse effects can be increased when Dihydrotachysterol is combined with Alfacalcidol.

Aluminum hydroxide +  Dihydrotachysterol :

The serum concentration of Aluminum hydroxide can be increased when it is combined with Dihydrotachysterol.

Aminophylline + Dihydrotachysterol :

The serum concentration of Aminophylline can be increased when it is combined with Dihydrotachysterol.

Bendroflumethiazide + Dihydrotachysterol :

Bendroflumethiazide may increase the hypercalcemic activities of Dihydrotachysterol.

Betamethasone + Dihydrotachysterol :

The risk or severity of adverse effects can be increased when Dihydrotachysterol is combined with Betamethasone.

Calcipotriol + Dihydrotachysterol :

The risk or severity of adverse effects can be increased when Dihydrotachysterol is combined with Calcipotriol.

THERAPEUTIC USES  :   

* Prophylaxis and treatment of nutritional vit D deficiency

* Metabolic rickets

* vit D resistant rickets

* Senile or postmenopausal osteoporosis

* Hypoparathyroidism

*Fanconi syndrome

ADVERSE EFFECT :

Nausea

Vomiting

Headache

REFERENCE:-Tripathi K D"Essential of medical pharmacology",7th edition ,page no.342,343