Posology : מינונים

4.2        Posology and method of administration

General
The dosage and administration of Alpha D3 should be adjusted according to the indication-specific notes which follow.

The initial dosage for all indications, excepting osteoporosis, is as follows: 
Adults and children 20 kg and over bodyweight:              1 mcg/day Elderly patients:                                         0.5 mcg/day 
The recommended dosage in osteoporosis is 0.5 mcg/day. It should not be exceeded.

The dose should subsequently be adjusted to avoid hypercalcaemia, according to the biochemical response. Plasma calcium levels (preferably corrected for protein binding) should initially be measured weekly. The dose of Alpha D3 can be increased by increments of 0.25 to 0.5 mcg/day. Most adults respond to doses of 1 to 3 mcg/day. Once the dose is stabilised, calcium levels may be measured every 2-4 weeks.
Indices of response, in addition to a rise in plasma calcium, may include alkaline phosphatase, parathyroid hormone levels, bone radiography and histological investigations. When there is biochemical or radiographic evidence of bone healing (or in hypoparathyroidism when calcium levels have normalised) the dose required for maintenance generally decreases to around 0.25 to 2 microgram/day. Should hypercalcaemia occur, Alpha D3 should be stopped until plasma calcium returns to normal (usually about a week) then restarted at one half of the previous dose.
Renal Bone Disease (Renal Osteodystrophy)
Patients with already high plasma calcium levels may have autonomous hyperparathyroidism. In this situation they may not respond to alfacalcidol and other therapeutic measures may be indicated.
In patients with chronic renal disease it is particularly important to check the plasma calcium frequently because prolonged hypercalcaemia may further impair renal function.
Before and during Alpha D3 treatment, the use of phosphate binding agents to prevent hyperphosphataemia may also be considered.

Hypoparathyroidism
Low plasma calcium levels may be restored to normal more quickly with Alpha D3 than with parent Vitamin D. Severe hypocalcaemia is corrected more rapidly with higher doses of Alpha D3 (e.g., 3-5 mcg) together with calcium supplements.

Hyperparathyroidism
In patients needing surgery for primary or tertiary hyperparathyroidsim, pre- operative treatment with Alpha D3 for 2-3 weeks can reduce bone pain and myopathy without aggravating hypercalcemia. To decrease the risk of post- operative hypocalcaemia, Alpha D3 should be continued until the plasma alkaline phosphatase falls to normal or hypercalcaemia occurs.

Nutritional and Malabsorptive Rickets and Osteomalacia
Malabsorptive osteomalacia, which responds to large doses of I.M. or I.V.
parent Vitamin D, will respond to small oral doses of Alpha D3. Nutritional rickets and osteomalacia can also be rapidly cured with Alpha D3.

Hypophosphatemic Vitamin D-Resistant Rickets and Osteomalacia Normal doses of Alpha D3 rapidly relieve myopathy, when present, and increase calcium and phosphate retention. Phosphate supplements may also be required in some patients. Neither large doses of parent Vitamin D nor phosphate supplements are entirely satisfactory in these conditions.

Pseudo-Deficiency (D-Dependent Type I) Rickets and Osteomalacia As with the nutritional conditions, similar oral doses of Alpha D3 are effective in circumstances which would require high doses of parent Vitamin D.

Osteoporosis
Serum calcium and creatinine levels should be determined at 1, 3 and 6 months, and at 6 monthly intervals thereafter.
The dose of Alpha D3 should be carefully adjusted for each patient according to the biological response so as to avoid hypercalcaemia.

Use in Children
Alfa D3 capsules are not indicated in children under 20kg as the dosage cannot be titrated adequately.

Use in Elderly
The clinical manifestations of hypo- or hyper calcaemia should be considered especially in elderly patients with pre-existing renal or heart conditions.