Pharmacology of Calcium Metabolism
Drugs used to treat Hypocalcemia
Calcium Salts -
- Calcium Carbonate
- Calcium Citrate
- Calcium Lactate
- Calcium gluconate
Ø use with caution in patients on Digitalis
Vitamin D preparations
- drugs of choice for treatment of Chronic hypocalcemia
- several preps
- DHT – dihydrotachysterol
Ø duration of action – 2 weeks
Ø requires liver and kidney for metabolism
Ø $20/week
- 25-(OH)-D3 – calcifediol
Ø duration of action – 2-3 weeks
Ø require kidney for metabolism
Ø t1/2= 20 hrs
Ø $10/week
- 1,25-(OH)2 – D3 – calcitriol
Ø quick time to max effect (3 min)
Ø duration of action – 3-5 days
Ø no requirements for metabolism
Ø t1/2= 15 hrs
Ø $45/week
- plain old D2 or D3
Ø requires liver or kidney for metabolism
Ø duration of action – 2 mths
Ø time to max effect – 4 weeks
Ø t1/2= 30
Ø $1/week
Thiazide Diuretics
Drugs to treat Hypercalcemia
Calcitonin
- useful in high doses for Paget’s disease treatment
- tolerance develops
- hypersecretion of PTH
Glucocorticoids
- major effect is on gut to reduce Ca2+ absorption
Furosemide
- administer with IV saline to insure adequate hydration
Bisphonates – sodium etidronate, alendronate
- analogues of pyrophosphate which bind directly to hydroxyapatite crystals in bone and impair resorption
- 50% of absorbed drug is bound to bone.
- Actually decreases both formation and resorption; net effect – decreased bone resorption
- Uses: Paget’s Disease, benign or malignant neoplasms, trauma, osteoporosis
- Adverse effects: GI disturbances (including GI bleeding)
Mithramycin
- 2nd line agent for Paget’s disease and hypercalcemia
- inhibits RNA synthesis; proteins are needed for bone resorption
- Toxic at high doses to rapidly proliferating cells
Fluoride
- may stimulate bone formation in the presence of Ca without affecting bone resorption
- forms abnormal crystal- less mechanical strength.
Drugs used to treat Osteoporosis
Ca2+ supplementation
Low dose Vitamin D
Estrogens
Alendronate
Calcitonin
Sodium Fluoride
SERMS – (Raloxifene)
- tissue specific effects
- Raloxifene is estrogen receptor AGONIST in the bone and the liver
- ANTAGONIST in the uterus and brain
- Actions
Ø decreases rate of bone loss
Ø decreases LDL
Ø Side effect: increases post-menopausal symptoms
Exercise
Tags: bone loss, Calcitonin, Digitalis, Drugs to treat Hypercalcemia, Drugs used to treat Osteoporosis, Furosemide, Glucocorticoids, Hypocalcemia, post-menopausal symptoms, Thiazide Diuretics
