Block 4: Ca2+ and P Flashcards
What is the function of Ca2+?
- Muscle contraction
- Membrane action potential
- Coagulation cascade
- Bone metabolism
Where is Ca2+ stored?
- Bone
- Serum
How is calcium regulated?
Vitamin D: carrier of Ca2+
Mg increases the absorption of Ca2+ (PTH)
PTH: ↑ Ca2+ → ↑ calcitonin →↓ Ca2+ absorption
How much of Ca2+ is in the body?
99% in bone
1% EC (40% is bound to albumin and rest is free calcium)
How do you calculate corrected calcium?
Corrected Calcium = Measured Ca + 0.8 (4- albumin)
What is normal serum total calcium?
8.4-10.2 mg/dL (2.1 to 2.55 mmol/L)
What is the normal serum ionized calcium?
4.48 to 5.32 mg/dL (1.12 to 1.33 mmol/L)
Describe the homeostasis of Ca2+
What is hypercalcemia?
> 10.2 mg/dL
Mild to moderate: 10.2 - 13 mg/dL
Severe: >13 mg/dL
Crisis: > 15 mg/dL
What are the causes of hypercalemia?
- Primary hyperPT
- Cancer secretions
- Immobilization
What drugs induce hypercalcemia?
Thiazides, Vit D, Lithium
What mechanisms are affected by hypercalcemia?
- Bone resorption (cancer, HPT)
- Increases calcium absorption in GIT (Vit D)
- Tubular reabsorption (thiazide, lithium)
What are the indications of mild to moderate Hyper calcemia?
<13
Asymptomatic
Drug induced or primary hyperparathyroidism
What are the indications of severe hypercalcemia (acute and chronic)?
> 13
Acute: N/V, constipation, polyuria, polydipsia
Chronic: calcification, nbephrolithiasis
What are the indications from hypercalcemic crisis?
> 15
AKI, Lethargy → chronic can lead to coma and life-threatening arrhythmias
Describe the treatment plan for hypercalcemia?
What is the first line for hypercalcemia?
0.9% NS
Loop diuretics
What are 1st lines for cancer associated hypercalcemia?
Pamidronate
Zoledronate
What should be used during refractory to bisphosphonate?
Denosumab (Xgeva not Prolia)
What is the function of calcitonin?
Inhibits bone resorption of Ca2+, inhibit absorption by intestine
Effectiveness can be increased if CS are added
CI of calcitonin? ADRs?
CHF, renal failure
Flushing, N/V, allergic reactions
What do you need to do prior to giving calcitonin?
10 units SQ test dose prior to starting therapy → continue with dosing if no erythema within 15 minutes
What is the MOA of bisphosphate?
Block bone resorption and inhibit osteoclast precursors
What are the first line for hypercalcemia caused by cancer?
Bisphosphates
Types of bisphosphates and dosing?
Pamidronate 30-90 mg IV over 2-24 hr
Zoledronic acid 4 mg IV over 15 minutes
ADR of using bisphosphates? CI? Warning?
ATN, jaw osteonecrosis
Severe renal impairment requiring dosing mod
Get dental work before use
What is the MOA of Denosumab? When should it be used?
Inhibitor principal mediator of osteoclast survival
If bisphosphates don’t work
ADR of Denosumab?
Jaw osteonecrosis, hungry bone, severe hypocalemiaW
How do the brands of denosumab differ?
Prolia (osteoporosis)
Xgeva (hypercalcemia if bisphosphate failed)
What is the GC indication? MOA?
- hypercalemia of myeloma, leukemia, lymphoma, sarcoidosis, combo with calcitonin
Can prevent tachyphylaxis of salmon calcitonin
Reduce GI absorption of calcium
ADRs of GC?
Hyperglycemia, osteoporosis, infection risk
How should GC be dosed for hypercalcemia?
Dosing: 200-400 mg HC equivalents IV daily, then pred 10-20 mg daily x 7 days
What is cinacalcet? Indication?
A calcimimetic that increases CaSr sensitivity resulting in lower PTH and serum Ca
Primary/secondary hyperPT
How do you dose cinacalcet?
Titrate Q2-4w in 30 mg increments
Max dose 90mg PO QID
What is the treatment of hypercalcemia in patients without heart or kidney impairment?
NS +/- loop diuretic for hydration and return to normal calcium level within 24-48 hr
What is the treatment of hypercalcemia in patients with renal and HF?
Hemodialysis
Calcitonin
≥4 months: body can develop antibody → ↓ effect of calcitonin
Add prednisone
What is the treatment of hypercalcemia in patients with primary/secondary hyperPT or parathyroid carcinoma?
- Cinacalcet (PO)
- Etelcalcetide (IV): for secondary (5 mg IV blood 3xwk at the end of dialysis
What is the treatment of hypercalcemia in cancer patients?
- Bisphosphate: Pamidronate and zoledronic acid (more potent and better response)
- Denosumab in refractory to bisphosphate (cost more)
What is hypocalcemia?
- Serum <8.6
- Ionized <4.4
What are the causes of hypocalcemia?
- low PTH from Operations and Mg def
- Vitamin D def
- Drugs
What drugs cause hypocalcemia?
- Sodium phosphate
- Phenobarbital, phenytoin, ketoconazole (CYP3A4)
- Furosemide
- Calcitonin
- Cinacalcet
- Bisphosphate and denosumab
What are the the acute symptoms of hypocalcemia?
- Tetany
- Paresthesias
- Seizure
What are the the chronic symptoms of hypocalcemia?
Depression and confusion
What are the the dermatologic symptoms of hypocalcemia?
Hairloss, grooved and brittle nails
What is the daily dose of elemental Ca?
1-3 g/day
What are the ADRs of PO calcium?
Constipation
What are the PO calcium salts and amount of elemental Ca?
Carbonate 40%
Acetate 25%
Citrate 21%
What are the IV Ca salts and mEq?
Chloride: 1g CaCl = 13.6 mEq Ca
Gluconate: 1g of CaG = 4.6 mEQ Ca
Preferred in alert patients
How often should IV calcium be monitored?
4-6 hrs
What is the hypocalcemia treatment if the corrected Ca <8.5 mg/dL
What is the hypocalcemia treatment is patient is symptomatic-acute with <7 Ca?
What is the function of phosphorus?
- Source of ATP
- Regulate cell metabolism
- Bone and teeth health
- Blood buffer system
How is phosphorus regulated?
PTH, FGF 23
Describe the homeostasis of phosphorus?
What are the normal values of phosphorus?
3-4.5 mg/dL
What is hyperphosphatemia? What are the causes?
> 4.5
1. Renal failure
2. Tumor lysis
3. Hemolysis
4. Rhabdo
5. HypoPT
6. Acidosis
What are the presentations of hyperphosphatemia?
- N/V
- Lethargy
- Seizures
- EV calcifications
- Nephrolithiasis
- Hypocalcemia from low PTH
- Red eye and pruritus (chronic)
Why does P increase when Ca decreases?
PTH compensates with lack of Ca by increasing P release
How do you treat hyperP in hypocalcemia patients?
IV calcium
How do you treat hyperP if norm or hyper calcemic?
Phosphate binders
How do you treat hyperP if symptomatic and failed other therapies?
Hemodialysis
What are the types of phosphate binders?
- Calcium based (Carbonate and acetate)
- Resins (Sevelamer HCl and carbonate)
- iron based (ferric citrate and sucroferric oxyhydroxides)
- Lanthanum carbonate
Out of the the iron based phosphate bind which ↑ Fe levels?
Ferric citrate
Sucroferric oxyhydroxides doesn’t effect Fe or Ca
What is the difference between phosphate binding resins?
Sevelamer HCl worsens acidosis
Carbonate: basic
When should calcium based Phosphate binders not be used?
Hypercalcemia
What are the ADRs of phosphate binders?
- Constipation
- NVD
- Hypercalcemia with Ca-based
- Iron overload with ferric citrate
What is the max elemental Ca?
1500mg/day
How do you dose calcium carbonate?
1 tab (500mg) TID w/ meals (200 mg of elemental)
What are the counseling points of calcium carbonate?
- Drug interactions with acid suppressors
- Give prior to meals to increase solubility
How do you dose calcium acetate?
2 cap (667mg) PO TID with melas (169 of elemental)
How does calcium acetate differ from carbonate?
- Bids 2x better to P
- Less affected by gastric pH
What are the similarities of resin binders?
Initial Dose: 800 mg TID with meals
Decreases LDL and ↑ HDL
Cost the same
What is the difference between sevelamer HCl and carbonate?
HCl: risk of metabolic acidosis
Carbonate comes in powder form
Dosing of ferric citrate? Counseling points?
2 tabs TID with meals
Increases iron levels
How does sucroferric oxyhydrate differ from ferric citrate?
500 mg TID with meals
1. Chewable formatin
2. Lower pill burdern
3. Longer effects
4. Doesn’t ↑ iron
How does lanthanum differ from other P binders?
Dosing: 500 mg TID with meals
Chewable and powder formulations
High binding capacity
Poor GI absorption: localized
Cost is higher
What are causes of hypophosphatemia?
- Reduced GI absorption
- Reduced tubular reabsorption
- Cellular redistribution
What are causes of reduced GI absorption of P?
- Alcholism
- Diarrhea, anorexia
- Phosphate binders
What are causes of reduced tubular reabsorption of P?
- Diuretics, GC, sodium bicarbonate, ferric carboxymaltose
- HyperPT
What are causes of cellular redistribution of P?
Refeeding
Dextrose, glucagon, insulin, calciton
What are the presentations of hypophosphatemia?
- Neuromuscular: weakness, paralysis (respiratory failure)
- Rhabdomyolysis
- Asymptomatic unless <1.5 mg/dL
What is hypophophatemia?
<2.7 mg/dL
What is referring syndrome?
When would IV P be used?
<1.5 or symptomatic
Weight based: 0.32-0.64 mmol/kg
What are the salt forms of IV P?
Sodium phosphate 1mmol=4mEq Na
Potassium phosphate
1mmol =4.4 mEq K
ADRs of IV P?
Ca/P product deposition, hypocalcemia
When is PO P used?
1.5-3 and asymptomatic
ADRs of PO P?
Diarrhea
What PO P is for high sodium and K levels?
K-Phos No2
What PO P is for low K levels?
Phos-NaK packet
What are the dangers of using Ca/P IV?
Cal (mEq/L) x Phosphate (mEq/L) > 55-60 results in precipitation and deposition of complexes in vasculature
- Careful with admixtures
- Less risk with gluconate