Merish Ct

Merish Ct Uses, Dosage, Side Effects, Food Interaction and all others data.

Calcitriol is one of the most important active metabolites of vitamin D3. It is normally formed in the kidney from its precursor, 25-hydroxycolecalciferol (25-HCC). Physiological daily production is normally 0.5-1.0 mcg and is somewhat higher during periods of increased bone synthesis (e.g. growth or pregnancy). Calcitriol promotes intestinal absorption of Calcium and regulates bone mineralization.

Calcitriol is a biologically active calcitrophic hormone with anti-osteoporotic, immunomodulatory, anticarcinogenic, antipsoriatic, antioxidant, and mood-modulatory activities. Its main sites of action are the intestine, bone, kidney and parathyroid hormone . Calcitriol is a ligand for the vitamin D nuclear receptor, which is expressed in, but not limited to, gastrointestinal (GI) tissues, bones, and kidneys . As an active form of vitamin D3, calcitriol elevates the plasma levels of calcium by stimulating intestinal calcium uptake, increasing reabsorption of calcium by the kidneys, and possibly increasing the release of calcium from skeletal stores. The duration of pharmacologic activity of a single dose of exogenous calcitriol is expected to be about 3 to 5 days .

In addition to its important role in calcium metabolism, other pharmacological effects of calcitriol have been studied in various conditions including cancer models. Various studies demonstrated expression of vitamin D receptors in cancer cell lines, including mouse myeloid leukemia cells . Calcitriol has been found to induce differentiation and/or inhibit cell proliferation in vitro and in vivo in many cell types, such as malignant cell lines carcinomas of the breast, prostate, colon, skin, and brain, myeloid leukemia cells, and others . In early human prostate cancer trials, administration of 1.5 µg/d calcitriol in male participants resulted in a reduction in the rate of PSA rise in most participants, however it was coincided with dose-limiting hypercalcemia in most participants . Hypercalcemia and hypercalcuria were evident in numerous initial trials, and this may be due to these trials not testing the drug at concentrations that are active in preclinical systems . Findings from preclinical data show an additive or synergistic antineoplastic action of calcitriol when combined with agents including dexamethasone, retinoids, and radiation, as well as several cytotoxic chemotherapy drugs such as platinum compounds .

Vitamin D deficiency has long been suspected to increase the susceptibility to tuberculosis. The active form of calcitriol, 1,25-(OH)2-D3, has been found to enhance the ability of mononuclear phagocytes to suppress the intracellular growth of Mycobacterium tuberculosis. 1,25-(OH)2-D3 has demonstrated beneficial effects in animal models of such autoimmune diseases as rheumatoid arthritis. Vitamin D appears to demonstrate both immune-enhancing and immunosuppressive effects.

Calcium citrate is a salt typically used as a source of calcium in a variety of over the counter supplements.

Increases plasma calcium levels leading to a decrease in calcium flux and increase in calcium deposition into bone

Folic acid is essential for the production of certain coenzymes in many metabolic systems such as purine and pyrimidine synthesis. It is also essential in the synthesis and maintenance of nucleoprotein in erythropoesis. It also promotes WBC and platelet production in folate-deficiency anaemia.

Folic acid is a water-soluble B-complex vitamin found in foods such as liver, kidney, yeast, and leafy, green vegetables. Also known as folate or Vitamin B9, folic acid is an essential cofactor for enzymes involved in DNA and RNA synthesis. More specifically, folic acid is required by the body for the synthesis of purines, pyrimidines, and methionine before incorporation into DNA or protein. Folic acid is the precursor of tetrahydrofolic acid, which is involved as a cofactor for transformylation reactions in the biosynthesis of purines and thymidylates of nucleic acids. Impairment of thymidylate synthesis in patients with folic acid deficiency is thought to account for the defective deoxyribonucleic acid (DNA) synthesis that leads to megaloblast formation and megaloblastic and macrocytic anemias. Folic acid is particularly important during phases of rapid cell division, such as infancy, pregnancy, and erythropoiesis, and plays a protective factor in the development of cancer. As humans are unable to synthesize folic acid endogenously, diet and supplementation is necessary to prevent deficiencies. In order to function properly within the body, folic acid must first be reduced by the enzyme dihydrofolate reductase (DHFR) into the cofactors dihydrofolate (DHF) and tetrahydrofolate (THF). This important pathway, which is required for de novo synthesis of nucleic acids and amino acids, is disrupted by anti-metabolite therapies such as Methotrexate as they function as DHFR inhibitors to prevent DNA synthesis in rapidly dividing cells, and therefore prevent the formation of DHF and THF.

In general, folate serum levels below 5 ng/mL indicate folate deficiency, and levels below 2 ng/mL usually result in megaloblastic anemia.

Pyridoxine is a water-soluble vitamin which functions in the metabolism of carbohydrates, proteins and fats. It is essential in Hb formation and GABA synthesis within the CNS. It also aids in the release of glycogen stored in the liver and muscles.

Vitamin B6 (pyridoxine) is a water-soluble vitamin used in the prophylaxis and treatment of vitamin B6 deficiency and peripheral neuropathy in those receiving isoniazid (isonicotinic acid hydrazide, INH). Vitamin B6 has been found to lower systolic and diastolic blood pressure in a small group of subjects with essential hypertension. Hypertension is another risk factor for atherosclerosis and coronary heart disease. Another study showed pyridoxine hydrochloride to inhibit ADP- or epinephrine-induced platelet aggregation and to lower total cholesterol levels and increase HDL-cholesterol levels, again in a small group of subjects. Vitamin B6, in the form of pyridoxal 5'-phosphate, was found to protect vascular endothelial cells in culture from injury by activated platelets. Endothelial injury and dysfunction are critical initiating events in the pathogenesis of atherosclerosis. Human studies have demonstrated that vitamin B6 deficiency affects cellular and humoral responses of the immune system. Vitamin B6 deficiency results in altered lymphocyte differentiation and maturation, reduced delayed-type hypersensitivity (DTH) responses, impaired antibody production, decreased lymphocyte proliferation and decreased interleukin (IL)-2 production, among other immunologic activities.

Merish Ct
Uses
Dosage
Side Effect
Precautions
Interactions
Uses during Pregnancy
Uses during Breastfeeding
Accute Overdose
Food Interaction
Half Life
Volume of Distribution
Clearance
Interaction With other Medicine
Contradiction
Storage

Trade Name	Merish Ct
Generic	Calcium Citrate + Calcitriol + Folic Acid + Methylcobalamin + Pyridoxine
Type	Capsule
Therapeutic Class
Manufacturer	Broad Injectable
Available Country	India
Last Updated:	September 19, 2023 at 7:00 am

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.

Calcium citrate is an ingredient found in a variety of supplements and vitamins.

For use as an over the counter calcium supplement.

Prophylaxis of megaloblastic anaemia in pregnancy, Supplement for women of child-bearing potential, Folate-deficient megaloblastic anaemia, Prophylaxis of neural tube defect in pregnancy

Pyridoxine (vitamin B6) is used to prevent or treat low levels of vitamin B6 in people who do not get enough of the vitamin from their diets. Most people who eat a normal diet do not need extra vitamin B6. However, some conditions (such as alcoholism, liver disease, overactive thyroid, heart failure) or medications (such as isoniazid, cycloserine, hydralazine, penicillamine) can cause low levels of vitamin B6. Vitamin B6 plays an important role in the body. It is needed to maintain the health of nerves, skin, and red blood cells.

Pyridoxine has been used to prevent or treat a certain nerve disorder (peripheral neuropathy) caused by certain medications (such as isoniazid). It has also been used to treat certain hereditary disorders (such as xanthurenic aciduria, hyperoxaluria, homocystinuria).

Merish Ct is also used to associated treatment for these conditions: Hypocalcemia, Osteodystrophy, Psoriasis Vulgaris (Plaque Psoriasis), Secondary Hyperparathyroidism (SHPT), Vitamin D Resistant RicketsCalcium Deficiency, Deficiency of Vitamin D3, Deficiency, Vitamin D, Folate deficiency, Hypocalcemia, Iron Deficiency (ID), OsteoporosisAnaemia folate deficiency, Folate deficiency, Iron Deficiency (ID), Iron Deficiency Anemia (IDA), Latent Iron Deficiency, Neural Tube Defects (NTDs), Vitamin Deficiency, Methotrexate toxicity, Nutritional supplementationBackache, Dizziness, Fever, Headache, Hepatic; Functional Disturbance, Hepatitis, Iron Deficiency Anemia (IDA), Ketosis, Macrocytic anemia, Menière's Disease, Menstrual Distress (Dysmenorrhea), Metabolic Acidosis, Motion Sickness, Nausea and vomiting, Neuralgia, Sciatic, Neuritis, Neurological Conditions caused by B Vitamin Deficiency, Secondary anemia, Soreness, Muscle, Toothache, Toxinfectious state, Trigeminal Neuralgia (TN), Vitamin B1 deficiency, Vitamin B12 Deficiency, Vitamin B6 Deficiency, Vitamin Deficiency, Minor aches and pains, Minor pain, Nutritional supplementation, Supplementation, Vitamin supplementation, Wellness of the Liver

How Merish Ct 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 citrate increases plasma calcium levels. This reduces calcium flux from osteocyte activity by reducing the secretion of parathyroid hormone (PTH) . Calcium does this by stimulating a G-protein coupled calcium receptor on the surface of parathyroid cells. The reduction in calcium flux increases the amount of calcium deposited in bone resulting in an increase in bone mineral density. The reduction in PTH secretion also reduces the amount of vitamin D metabolized to its active form, calcidiol. Since calcidiol increases the expression of calcium dependent ATPases and transient receptor potential cation channel subfamily V member 6 (TRPV6) both of which are involved in calcium uptake from the gut, a reduction in calcidiol results in less calcium absorption. Additionally, TRPV5, the channel responsible for calcium reabsorption in the kidney, is downregulated when PTH secretion is reduced thus increasing calcium excretion via the kidneys. Another hormone, calitonin, is likely involved in the reduction of bone resorption during periods of high plasma calcium.

Folic acid, as it is biochemically inactive, is converted to tetrahydrofolic acid and methyltetrahydrofolate by dihydrofolate reductase (DHFR). These folic acid congeners are transported across cells by receptor-mediated endocytosis where they are needed to maintain normal erythropoiesis, synthesize purine and thymidylate nucleic acids, interconvert amino acids, methylate tRNA, and generate and use formate. Using vitamin B12 as a cofactor, folic acid can normalize high homocysteine levels by remethylation of homocysteine to methionine via methionine synthetase.

Vitamin B6 is the collective term for a group of three related compounds, pyridoxine (PN), pyridoxal (PL) and pyridoxamine (PM), and their phosphorylated derivatives, pyridoxine 5'-phosphate (PNP), pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP). Although all six of these compounds should technically be referred to as vitamin B6, the term vitamin B6 is commonly used interchangeably with just one of them, pyridoxine. Vitamin B6, principally in its biologically active coenzyme form pyridoxal 5'-phosphate, is involved in a wide range of biochemical reactions, including the metabolism of amino acids and glycogen, the synthesis of nucleic acids, hemogloblin, sphingomyelin and other sphingolipids, and the synthesis of the neurotransmitters serotonin, dopamine, norepinephrine and gamma-aminobutyric acid (GABA).

Dosage

Merish Ct 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.

Supplement for women of child-bearing potential: 0.4 mg daily.

Folate-deficient megaloblastic anaemia: 5 mg daily for 4 mth, up to 15 mg daily in malabsorption states. Continued dosing at 5 mg every 1-7 days may be needed in chronic haemolytic states, depending on the diet and rate of haemolysis.

Prophylaxis of neural tube defect in pregnancy: 4 or 5 mg daily starting before pregnancy and continued through the 1st trimester.

Prophylaxis of megaloblastic anaemia in pregnancy: 0.2-0.5 mg daily.

ADULTS:

BY MOUTH:

For hereditary sideroblastic anemia: Initially, 200-600 mg of vitamin B6 is used. The dose is decreased to 30-50 mg per day after an adequate response.
For vitamin B6 deficiency: In most adults, the typical dose is 2.5-25 mg daily for three weeks then 1.5-2.5 mg per day thereafter. In women taking birth control pills, the dose is 25-30 mg per day.
For abnormally high levels of homocysteine in the blood: For reducing high levels of homocysteine in the blood after childbirth, 50-200 mg of vitamin B6 has been taken alone. Also, 100 mg of vitamin B6 has been taken in combination with 0.5 mg of folic acid.
For preventing macular degeneration: 50 mg of vitamin B6 in the form of pyridoxine has been used daily in combination with 1000 mcg of vitamin B12 (cyanocobalamin) 1000 mcg and 2500 mcg of folic acid for about 7 years.
For hardening of the arteries (atherosclerosis): A specific supplement (Kyolic, Total Heart Health, Formula 108, Wakunga) containing 250 mg of aged garlic extract, 100 mcg of vitamin B12, 300 mcg of folic acid, 12.5 mg of vitamin B6, and 100 mg of L-argininedaily for 12 months.
For kidney stones: 25-500 mg of vitamin B6 has been used daily.
For nausea during pregnancy: 10-25 mg of vitamin B6 taken three or four times per day has been used. In people who don't respond to vitamin B6 alone, a combination product containing vitamin B6 and the drug doxylamine (Diclectin, Duchesnay Inc.) is used three or four times per day. Also, another product containing 75 mg of vitamin B6, 12 mcg of vitamin B12, 1 mg of folic acid, and 200 mg of calcium (PremesisRx, KV Pharmaceuticals) is used daily.
For symptoms of premenstrual syndrome (PMS): 50-100 mg of vitamin B6 is used daily, alone or along with 200 mg of magnesium.
For treating tardive dyskinesia: 100 mg of vitamin B6 per day has been increased weekly up to 400 mg per day, given in two divided doses.

INJECTED INTO THE MUSCLE:

Hereditary sideroblastic anemia: 250 mg of vitamin B6 daily, reduced to 250 mg of vitamin B6 weekly once adequate response is achieved.

CHILDREN:

BY MOUTH:

For kidney stones: Up to 20 mg/kg daily in children aged 5 years and up.

INJECTED INTO THE VEIN OR MUSCLE:

For seizures that respond to vitamin B6 (pyridoxine-dependent seizures): 10-100 mg is recommended.

The daily recommended dietary allowances (RDAs) of vitamin B6 are:

Infants 0-6 months, 0.1 mg
Infants 7-12 months, 0.3 mg
Children 1-3 years, 0.5 mg
Children 4-8 years, 0.6 mg
Children 9-13 years, 1 mg
Males 14-50 years, 1.3 mg
Males over 50 years, 1.7 mg
Females 14-18 years, 1.2 mg
Females 19-50 years, 1.3 mg
Females over 50 years, 1.5 mg
Pregnant women, 1.9 mg
Breast-feeding women, 2 mg
Some researchers think the RDA for women 19-50 years should be increased to 1.5-1.7 mg per day.

The recommended maximum daily intake is:

Children 1-3 years, 30 mg
Children 4-8 years, 40 mg
Children 9-13 years, 60 mg

Adults, pregnant and breast-feeding women:

14-18 years, 80 mg
over 18 years, 100 mg

May be taken with or without food.

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.

GI disturbances, hypersensitivity reactions; bronchospasm.

Pyridoxine usually has no side effects when used in recommended doses.

If your doctor has prescribed this medication, remember that he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Pyridoxine can cause side effects when taken in large doses for a long time. Tell your doctor right away if any of these unlikely but serious side effects occur: headache, nausea, drowsiness, numbness/tingling of arms/legs.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

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 .

Patients taking more than 4g of calcium a day are at risk of hypercalcemia and metabolic alkalosis . Chronic intake of calcium supplements is associated with adverse gastrointestinal symptoms such as constipation and flatulence .

IPR-MUS LD₅₀ 85 mg/kg,IVN-GPG LD₅₀ 120 mg/kg, IVN-MUS LD₅₀ 239 mg/kg, IVN-RAT LD₅₀ 500 mg/kg, IVN-RBT LD₅₀ 410 mg/kg

Oral Rat LD50 = 4 gm/kg. Toxic effects include convulsions, dyspnea, hypermotility, diarrhea, ataxia and muscle weakness.

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.

Treatment resistance may occur in patients with depressed haematopoiesis, alcoholism, deficiencies of other vitamins. Neonates.

Before taking pyridoxine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

During pregnancy, this vitamin has been found to be safe when used in recommended doses.

This vitamin passes into breast milk and is considered to be safe during breast-feeding when used in recommended doses. Consult your doctor for more information.

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.

Antiepileptics, oral contraceptives, anti-TB drugs, alcohol, aminopterin, methotrexate, pyrimethamine, trimethoprim and sulphonamides may result to decrease in serum folate contrations. Decreases serum phenytoin concentrations.

The effects of some drugs can change if you take other drugs or herbal products at the same time. This can increase your risk for serious side effects or may cause your medications not to work correctly. These drug interactions are possible, but do not always occur. Your doctor or pharmacist can often prevent or manage interactions by changing how you use your medications or by close monitoring.

To help your doctor and pharmacist give you the best care, be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products) before starting treatment with this product. While using this product, do not start, stop, or change the dosage of any other medicines you are using without your doctor's approval.

Some products that may interact with this vitamin include: altretamine, cisplatin, phenytoin.

This vitamin may interfere with certain laboratory tests (including urine test for urobilinogen), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this vitamin.

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 .

Tetrahydrofolic acid derivatives are distributed to all body tissues but are stored primarily in the liver.

Pyridoxine main active metabolite, pyridoxal 5’-phosphate, is released into the circulation (accounting for at least 60% of circulating vitamin B6) and is highly protein bound, primarily to albumin.

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 .

The percentage of calcium absorbed varies inversely with intake . Tmax of about 3.5-5h varying with formulation .

Folic acid is absorbed rapidly from the small intestine, primarily from the proximal portion. Naturally occurring conjugated folates are reduced enzymatically to folic acid in the gastrointestinal tract prior to absorption. Folic acid appears in the plasma approximately 15 to 30 minutes after an oral dose; peak levels are generally reached within 1 hour.

The B vitamins are readily absorbed from the gastrointestinal tract, except in malabsorption syndromes. Pyridoxine is absorbed mainly in the jejunum. The Cmax of pyridoxine is achieved within 5.5 hours.

Half Life

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

The total adult body pool consists of 16 to 25 mg of pyridoxine. Its half-life appears to be 15 to 20 days.

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 .

Cleared via the kidneys but largely reabsorbed (98-99%) under normal conditions .

After a single oral dose of 100 mcg of folic acid in a limited number of normal adults, only a trace amount of the drug appeared in the urine. An oral dose of 5 mg in 1 study and a dose of 40 mcg/kg of body weight in another study resulted in approximately 50% of the dose appearing in the urine. After a single oral dose of 15 mg, up to 90% of the dose was recovered in the urine. A majority of the metabolic products appeared in the urine after 6 hours; excretion was generally complete within 24 hours. Small amounts of orally administered folic acid have also been recovered in the feces. Folic acid is also excreted in the milk of lactating mothers.

The major metabolite of pyridoxine, 4-pyridoxic acid, is inactive and is excreted in urine

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.

Pregnancy Category A. Adequate and well-controlled human studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy (and there is no evidence of risk in later trimesters).

Category A: Controlled studies in women fail to demonstrate a risk to the foetus in the 1st trimester (and there is no evidence of a risk in later trimesters), and the possibility of foetal harm remains remote.

Contraindication

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

Undiagnosed megaloblastic anaemia; pernicious, aplastic or normocytic anaemias.

Special Warning

Elderly patients: No specific dosage modifications are required in 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.