ERGOCALCIFEROL (er-goe-kal-si'fe-role)
Activated Ergosterol, Drisdol, D-ViSol, Ostoforte , Radiostol , Radiostol Forte , Vitamin D2 Classifications: vitamin d analog; Therapeutic:vitamin d analog Prototype: Calcitriol Pregnancy Category: C
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Availability
8000 IU/mL oral liquid; 50,000 units capsules, tablets; 500,000 IU/mL injection
Action
The name vitamin D encompasses two related fat-soluble substances (sterols) that occur in nature or are synthetically prepared.
Vitamin D acts like a hormone in that it is distributed through the circulation and plays a major regulatory role. Reponsible
for regulation of serum calcium level.
Therapeutic Effect
Maintains normal blood calcium and phosphate ion levels by enhancing their intestinal absorption and by promoting mobilization
of calcium from bone and renal tubular resorption of phosphate.
Uses
Familial hypophosphatemia (vitamin Dresistant rickets), osteomalacia (adult rickets), anticonvulsant-induced rickets
and osteomalacia, osteoporosis, renal osteodystrophy, hypocalcemia associated with hypoparathyroidism; prophylaxis and treatment
of nutritional rickets. Also hypophosphatemia in Fanconi's syndrome.
Unlabeled Uses
With varying clinical results in lupus vulgaris, psoriasis, and rheumatoid arthritis.
Contraindications
Hypersensitivity to vitamin D, hypervitaminosis D, hypercalcemia, hyperphosphatemia, renal osteodystrophy with hyperphosphatemia,
malabsorption syndrome, decreased kidney function. Safe use of amounts in excess of 400 IU (10 mcg) daily during pregnancy
(category C) is not established.
Cautious Use
Coronary disease; arteriosclerosis (especially in older adults); history of kidney stones; biliary tract disease; lactation.
Route & Dosage
Nutritional Rickets, Osteomalacia Adult: PO/IM 25125 mcg/d for 612 wk, may need up to 7.5 mg/d in patients with malabsorption Child: PO/IM 50125 mcg/d, may need up to 250625 mcg/d in patients with malabsorption
Vitamin DDependent Rickets Adult: PO/IM 250 mcg1.5 mg/d, may need up to 12.5 mg/d (prolonged therapy with >2.5 mg/d increases risk of toxicity) Child: PO/IM 75125 mcg/d, may need up to 1.5 mg/d
Hypoparathyroidism, Pseudohypoparathyroidism Adult: PO/IM 625 mcg5 mg/d, may need up to 10 mg/d (prolonged therapy with >2.5 mg/d increases risk of toxicity) Child: PO/IM 1.255 mg/d, (prolonged therapy with >2.5 mg/d increases risk of toxicity)
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Administration
- Note: 40 U = 1 mcg. Reduce dosage, once symptoms of vitamin D deficiency are relieved, to prevent hypercalcemia.
Intramuscular
- Give injection deeply, preferably into gluteus maximus and inject slowly. Aspirate carefully. Rotate injection sites.
- Preserve in tightly covered, light-resistant containers. Drug decomposes when exposed to light and air.
Adverse Effects (≥1%)
Body as a Whole: Fatigue, weakness, vertigo, tinnitus, ataxia, muscle and joint pain, hypotonia (infants), exanthema, rhinorrhea; pruritus;
mild acidosis.
CNS: Headache, drowsiness, convulsions.
GI: Metallic taste, dry mouth, anorexia, nausea, vomiting,
diarrhea,
constipation, abdominal cramps.
Hematologic: Anemia.
Musculoskeletal: Calcification of soft tissues (kidneys, blood vessels, myocardium, lungs, skin).
Urogenital: Nephrotoxicity (polyuria, hyposthenuria, polydipsia, nocturia, casts, albuminuria, hematuria), kidney failure.
CV: Hypertension, cardiac arrhythmias.
Special Senses: Conjunctivitis (calcific); photophobia.
Metabolic: Osteoporosis (adults); weight loss, chronic hypervitaminosis D in children (
mental and physical retardation, suppression of linear growth).
Diagnostic Test Interference
Vitamin D may cause false increase in serum cholesterol measurements (Zlatkis-Zak reaction).
Interactions
Drug: Cholestyramine, colestipol, mineral oil may decrease absorption of vitamin D.
Pharmacokinetics
Absorption: Readily from GI tract.
Peak: After 4 wk.
Duration: 2 mo or more.
Distribution: Most of drug first appears in
lymph, stored chiefly in liver and in skin, brain, spleen, and bones.
Metabolism: In liver and kidney to active metabolites.
Elimination: About 50% of PO dose in bile; may be stored in tissues for months.
Half-Life: 1224 h.
Nursing Implications
Assessment & Drug Effects
- Monitor closely patients receiving therapeutic doses of vitamin D; must remain under close medical supervision.
- Lab tests: When high therapeutic doses are used, progress is followed by frequent determinations (q2wk or more often) of serum
calcium, phosphorus, magnesium, alkaline phosphatase, BUN, and determinations of urine calcium, casts, albumin, and RBC. Blood
calcium concentration is generally kept between 9 and 10 mg/dL.
- Monitor for hypercalcemia; in patients with osteomalacia a decrease in serum alkaline phosphatase may signal the onset of
hypercalcemia.
Patient & Family Education
- Avoid magnesium-containing antacids and laxatives with chronic kidney failure when receiving vitamin D preparations since
vitamin D increases the risk of magnesium intoxication than other patients.
- Do not use OTC medications unless approved by physician.