Smira

Uses

Calcitriol is used for the correction of the abnormalities of Calcium and Phosphate metabolism in patients with renal osteodystrophy.

Calcitriol is also used for the treatment of established post-menopausal osteoporosis, hypoparathyroidism, idiopathic hypoparathyroidism, pseudohypoparathyroidism, vitamin D dependent rickets.

Adult: One Calcium Carbonate 500 tablet or as directed by the physician. For the prevention of osteoporosis, 1-3 Calcium Carbonate 500 tablet is recommended generally as a dietary supplement . Doses for children is half of those for adults. A large dose should not be taken without physician\'s advice.

Adolescent: One to two Calcium Carbonate tablet daily.

Children: One Calcium Carbonate tablet daily.

Smira is also used to associated treatment for these conditions: Hypocalcemia, Osteodystrophy, Psoriasis Vulgaris (Plaque Psoriasis), Secondary Hyperparathyroidism (SHPT), Vitamin D Resistant RicketsAcid Reflux, Acid indigestion, Bloating, Calcium Deficiency, Calcium Metabolism Disorders, Calcium and Vitamin D Deficiencies, Colic, Dyspepsia, Gastric Ulcer, Gastroesophageal Reflux, Heartburn, Hemorrhoids, Hot Flushes, Hyperacidity, Hyperphosphataemia, Hypovitaminosis D, Low Bone Density, Osteodystrophy, Osteomalacia, Osteoporosis, Postmenopausal Osteoporosis, Postoperative Gas, Proctitis, Vertebral Fractures, Calcium loss, Gastrointestinal ulceration, Dietary supplementation

How Smira works

The mechanism of action of calcitriol in the treatment of psoriasis is accounted for by their antiproliferative activity for keratinocytes and their stimulation of epidermal cell differentiation. The anticarcinogenic activity of the active form of Calcitriol appears to be correlated with cellular vitamin D receptor (VDR) levels. Vitamin D receptors belong to the superfamily of steroid-hormone zinc-finger receptors. VDRs selectively bind 1,25-(OH)₂-D3 and retinoic acid X receptor (RXR) to form a heterodimeric complex that interacts with specific DNA sequences known as vitamin D-responsive elements. VDRs are ligand-activated transcription factors. The receptors activate or repress the transcription of target genes upon binding their respective ligands. It is thought that the anticarcinogenic effect of Calcitriol is mediated via VDRs in cancer cells. The immunomodulatory activity of calcitriol is thought to be mediated by vitamin D receptors (VDRs) which are expressed constitutively in monocytes but induced upon activation of T and B lymphocytes. 1,25-(OH)₂-D3 has also been found to enhance the activity of some vitamin D-receptor positive immune cells and to enhance the sensitivity of certain target cells to various cytokines secreted by immune cells.

A study suggests that calcitriol plays an immunoregulatry role by suppressing the aryl hydrocarbon receptor (AhR) expression in human Th9, a pro-inflammatory CD4 T cell subset . This suppression subsequently leads to repressed expression of BATF, a transcription factor essential for Th9 . Calcitriol has also been found to induce monocyte differentiation and to inhibit lymphocyte proliferation and production of cytokines, including interleukin IL-1 and IL-2, as well as to suppress immunoglobulin secretion by B lymphocytes.

Calcium carbonate is a basic inorganic salt that acts by neutralizing hydrochloric acid in gastric secretions. It also inhibits the action of pepsin by increasing the pH and via adsorption. Cytoprotective effects may occur through increases in bicarbonate ion (HCO₃^-) and prostaglandins. Neutralization of hydrochloric acid results in the formation of calcium chloride, carbon dioxide and water. Approximately 90% of calcium chloride is converted to insoluble calcium salts (e.g. calcium carbonate and calcium phosphate).

Dosage

Smira dosage

Injection

The recommended intravenous initial dose of Calcitriol injection, depending on the severity of the hypocalcemia and/or secondary hyperparathyroidism, is 1 mcg (0.02 mcg/kg) to 2 mcg administered three times weekly, approximately every other day. Doses as small as 0.5 mcg and as large as 4 mcg three times weekly have been used as an initial dose. If a satisfactory response is not observed, the dose may be increased by 0.5 to 1 mcg at two to four week intervals.

Capsule

Adult

Renal osteodystrophy: The initial daily dose is 0.25 mcg of Calcitriol. In patients with normal or only slighty reduced Calcium level, doses of 0.25 mcg every other day are sufficient. If no satisfactory response in the biochemical parameters and clinical manifestations of the disease is observed within 2-4 weeks, the daily dosage may be increased by 0.25 mcg at 2-4 week intervals.

Post-menopausal osteoporosis: The recommended dose of Calcitriol is 0.25 mcg twice daily.

Serum calcium and creatinin levels should be determined at 1-3 and 6 months and at 6 monthly intervals thereafter.

Hypoparathyroidism & Rickets: The recommended initial dose of Calcitriol is 0.25 mcg per day in the morning. In patients with renal osteodystrophy or hypoparathyroidism and rickets if within 2-4 weeks no satisfactory response is observed by usual dose then dose may be increased at two to four week intervals.

Elderly patients

No specific dosage modifications are required in elderly patents.

Children

Dosage in children has not been established.

Calcium Carbonate is always used orally and when used as an antacid the recommended doses for adults are equivalent to 540-2000 mg Calcium Carbonate per day, doses for children being half of those for adults. As a dietary supplement, such as for the prevention of osteoporosis, 1250-3750 mg Calcium Carbonate (500-1500 mg calcium) daily is recommended in general, but again this will need to be tailored to the individual patient depending on any specific disease such as Calcium deficiency, malabsorption or parathyroid function. In pregnancy and lactation therecommended daily dose of calcium is 1200-1500 mg. In chronic renal failure the doses used vary from 2.5 - 9.0 gm Calcium Carbonate per day and need to be adjusted according to the individual patient. To maximize effective phosphate binding in this context the Calcium Carbonate should be given with meals.

Side Effects

Since Calcitriol exerts vitamin D activity, adverse effects may occur which are similar to those found when an excessive dose of vitamin D is taken, i.e. hypercalcaemia syndrome or calcium intoxication (depending on the severity and duration of hypercalcaemia). Occasional acute symptoms include anorexia, headache, nausea, vomiting, abdominal pain or stomach ache and constipation.

In rare cases, flatulence, diarrhoea or constipation.

Toxicity

LD₅₀ (oral, rat) = 620 μg/kg; LD₅₀ (intraperitoneal, rat) > 5 mg/kg .

Symptoms of calcitriol toxicity mirrors the early and late signs and symptoms of vitamin D intoxication associated with hypercalcemia . Early signs include weakness, headache, somnolence, nausea, vomiting, dry mouth, constipation, muscle pain, bone pain and metallic taste. Late signs are characterized by polyuria, polydipsia, anorexia, weight loss, nocturia, conjunctivitis (calcific), pancreatitis, photophobia, rhinorrhea, pruritus, hyperthermia, decreased libido, elevated BUN, albuminuria, hypercholesterolemia, elevated SGOT and SGPT, ectopic calcification, hypertension, cardiac arrhythmias and, rarely, overt psychosis .

Precaution

Immobilised patients, e.g. those who have undergone surgery, are particularly exposed to the risk of hypercalcaemia. Patients with normal renal function who are taking Calcitriol should avoid dehydration. Adequate fluid intake should be maintained.

In the presence of mild hypercalciuria, excretion levels must be carefully monitored and where necessary the dose of calcium carbonate should be reduced or treatment should be stopped. Patients with a history of stone formation should also be recommended to increase their fluid intake. High dosage of vitamin D should be avoided during Calcium therapy unless specifically indicated.

Interaction

Concomitant treatment with a thiazide diuretic increases the risk of hypercalcaemia. Calcitriol dosage must be determined with care in patients undergoing treatment with digitalis, as hypercalcaemia in such patients may precipitate cardiac arrhythmias. Administration of enzyme inducers such as phenytoin or phenobarbital may lead to increased metabolism and hence reduced serum concentrations of Calcitriol. Therefore higher doses of Calcitriol may be necessary if these drugs are administered simultaneously. Colestyramine can reduce intestinal absorption of fat-soluble vitamins and therefore may impair intestinal absorption of Calcitriol.

Oral calcium can reduce internal absorption of tetracycline and fluoride prepa-rations and an interval of at least 3 hours should therefore be allowed between ingestion of these medications. Vitamin D increases internal absorption of calcium. The intestinal uptake of calcium may be reduced by concomitant ingestion of certain foods (e.g. spinach, milk and milk products).

Volume of Distribution

Upon intravenous administration, the volume of distribution of calcitriol was 0.49±0.14 L/kg in healthy male volunteers and 0.27±0.06 l/kg in uraemic male patients participating in a pharmacokinetic study . There is some evidence that calcitriol is transferred into human milk at low levels (ie, 2.2±0.1 pg/mL) in mothers . Calcitriol from maternal circulation may also enter the fetal circulation .

Calcium is rapidly distributed taken up by skeletal tissues following absorption and distribution into extracellular fluids. Bone contains 99% of the body's calcium and the remaining 1% is approximately equally distributed between intracellular and extracellular fluids.

Elimination Route

Upon administration, calcitriol is rapidly absorbed from the intestines. When a single oral dose of 0.5 mcg of calcitriol was administered, the mean serum concentrations of calcitriol rose from a baseline value of 40.0±4.4 (SD) pg/mL to 60.0±4.4 pg/mL at 2 hours, and declined to 53.0±6.9 at 4 hours, 50±7.0 at 8 hours, 44±4.6 at 12 hours and 41.5±5.1 at 24 hours . Following administration of single doses of 0.25 to 1.0 mcg of calcitriol, the peak plasma concentrations were reached within 3 to 6 hours . In a pharmacokinetic study, the oral bioavailability was 70.6±5.8% in healthy male volunteers and 72.2±4.8% in male patients with uraemia .

Maximal absorption occurs at doses of 500 mg or less taken with food. Oral bioavailability depends on intestinal pH, the presence of food and dosage.

Half Life

After administration of single oral doses, the elimination half life was 5-8 hours .

Clearance

The metabolic clearance rate was 23.5±4.34 ml/min in healthy male volunteers and 10.1±1.35 ml/min in male patients with uraemia . In the pediatric patients undergoing peritoneal dialysis receiving dose of 10.2 ng/kg (SD 5.5 ng/kg) for 2 months, the clearance rate was 15.3 mL/hr/kg .

Elimination Route

In normal subjects, approximately 27% and 7% of the radioactivity appeared in the feces and urine, respectively, within 24 hours . Calcitriol undergoes enterohepatic recycling and biliary excretion. The metabolites of calcitriol are excreted primarily in feces. Cumulative excretion of radioactivity on the sixth day following intravenous administration of radiolabeled calcitriol averaged 16% in urine and 49% in feces .

Excreted mainly in the feces. The majority of renally filtered calcium is reabsorbed in the ascending limb of the loop of Henle and the proximal and distal convoluted tubules. Also secreted by sweat glands.

Pregnancy & Breastfeeding use

Pregnancy category C. Calcitriol has been found to be teratogenic in rabbits. There are no adequate and well-controlled studies in pregnant women. Calcitriol should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Pregnant women : Calcium containing drugs are used widely in pregnancy by way of calcium supplement or antacid therapy. No relationship between malformation in general and calcium exposure has been noted.

Lactating mother : There is no contraindication to the use of calcium carbonate in lactating mother.

Contraindication

Calcitriol is contraindicated in patients with known hypersensitivity to any of its ingredients. Calcitriol is also contraindicated in all diseases associated with hypercalcemia.

Hypersensitivity to the Calcium Carbonate or any inactive ingredient of the medication. Hypercalcemia (e.g. in hyperparathyroidism, overdosage of vitamin D, demineralizing tumours such as plasmacytomas and bone metastases), severe hypercalcuria, several renal insufficiency.

Special Warning

Elderly patients: No specific dosage modifications are required in elderly patients.

USE IN CHILDREN: Calcium carbonate has been extensively studied in children and infants with chronic renal failure and is both safe and effective.

USE IN ELDERLY: In case of elderly patients with renal failure when calcium carbonate is taken constipation may be troublesome one for this group. For this reason, monitoring of serum calcium and phosphate is of course indicated for elderly patients.

Acute Overdose

Administration of Calcitriol to patients in excess of their daily requirements can cause hypercalcaemia, hypercalciuria and hyperphospatemia. Since Calcitriol is a derivative of vitamin D, the signs and symptoms of overdose are the same as for an overdose of vitamin D.

Storage Condition

Store between 15-30° C. Protect from moisture, heat and light. Do not freeze.

Store in a cool, dry place in controlled room temperature.

Innovators Monograph

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