Agents that affect Calcium and Phosphate Homeostasis

Question 1

Calcium Supplements (6, 3 IV and 3 Oral)

Answer 1

IV- Ca chloride, Ca gluconate, Ca gluceptate

Oral- Ca carbonate, Ca citrate, Ca lactate

Question 2

Type of 4 Vitamin D analogs –> Cholecalciferol, Ergocalciferol, Calcifediol, and Calcitriol

Answer 2

Vitamin D3; Vitamin D2; 25-OH-cholecalciferol (liver adds 25-OH); 1, 25-dihydroxy-cholecalciferol

Question 3

Class of Dihydrotachysterol

Answer 3

Vitamin D synthetic derivative

Question 4

Tx w/Dihydrotachysterol (DHT) - 3 points, 4 diseases

Answer 4

1. Osteoporosis, hypocalcemia, hypoparathyroidism, nutritional deficiency
2. Can use w/patients w/renal disease
3. Does not require 1-OH for activation but does require 25-OH in liver

Question 5

How is cholecalciferol metabolized to calcitriol?

Answer 5

Cholecalciferol - Vitamin D3 
--> 25-hydroxylation in liver --> 
Calcifediol (25-OH-Cholecalciferol) 
--> 1-hydroxylation in kidney --> 
Calcitriol (1,25-dihydroxy-cholecalciferol)

Question 6

Calcifediol - Tx (3 points, 4 diseases)

Answer 6

1. Vitamin D analog of 25-hydroxycholecalciferol
2. Tx = osteoporosis, hypocalcemia, hypoparathyroidism, nutritional deficiency
3. Used in patients w/ hepatic disease (doesn’t require hepatic 25-hydroxylation)

Question 7

Does calcifediol require hepatic 25-hydroxylation?

Answer 7

No

Question 8

Calcitriol - Tx (3 points, 4 diseases)

Answer 8

1. Vitamin D analog of 1,25-dihydroxycholecalciferol 2. Tx = osteoporosis, hypocalcemia, hypoparathyroidism, nutritional deficiency
2. Used in patients w/ renal disease (doesn’t require hepatic 25-hydroxylation or renal 1-hydroxylation)

Question 9

Does calcifediol require hepatic 25-hydroxylation?

Answer 9

No (and neither renal 1-hydroxylation)

Question 10

What are the Vitamin D synthetic derivatives (3)?

Answer 10

1. Dihydrotachysterol (DHT)
2. 1-alpha-Hydroxycholecalciferol (Alfacalcidol)
3. Doxercalciferol (1-hydroxyvitamin D2)

Question 11

Doxercalciferol (1-hydroxyvitamin D2)
Alfacalcidol (1-alpha-Hydroxycholecalciferol)
- 4 points, 4 diseases

Answer 11

1. Vitamin D synthetic derivative
2. Tx = osteoporosis, hypocalcemia, hypoparathyroidism, nutritional deficiency
3. Already contains the 1-OH but requires 25-OH in liver
4. Able to use in patients w/ renal disease

Question 12

What are the Calcitriol analogs (2)?

Answer 12

1. Paricalcitol

2. 22-oxacalcitriol

Question 13

Paricalcitol (4 points)

Answer 13

1. Calcitriol analog
2. Reduces PTH w/o hypercalcemia
3. Used in chronic renal failure
4. Little GI action

Question 14

22-oxacalcitriol - Class and MOA

Answer 14

Calcitriol analog

MOA: suppressor of parathyroid hormone (PTH) gene expression

Question 15

22-oxacalcitriol - Tx

Answer 15

1. Limited action on intestine and bone

2. Chronic renal failure w/secondary hyperparathyroidism or in primary hyperparathyroidism

Question 16

Which one has a longer half-life: 22-oxacalcitriol or calcitriol? Why?

Answer 16

22-oxacalcitriol; low affinity for serum binding protein leads to longer half-life than calcitriol

Question 17

Sevelamer - Class and MOA

Answer 17

Phosphate binder/binding polymer

MOA: binds phosphate in the gut to prevent absorption

Question 18

Cinacalcet - Class

Answer 18

Calcimimetic

Question 19

Cinacalcet - MOA

Answer 19

Inhibits PTH secretion by lowering the concentration of Ca2+ at which PTH secretion is suppressed and thus enhances the sensitivity of the CaSR

Question 20

Cinacalcet - Tx

Answer 20

Secondary hyperparathyroidism due to chronic renal failure