L6. VitD, ZnP Flashcards
Vitamin D potency
Vitamin D2 (ergocalciferol) is the plant-derived form
Unit conversions:
Vitamin D2 crystals have a potency of 40,000units Vit. D/mg
One mg of cholecalciferol = 40,000 units Vit. D/mg
1USP or international unit = 25ng cholecaciferol or ergocalciferol
Vitamin D2:
Sources
- Pellet or ceral based baits contain 0.075%
- “Place packs 10-30g each
- Careless placement often leads to toxicosis in non-target species (dogs)
- Toxicosis in rodents delayed 2-3 days
- 1 IU of D3 = 0.025ug (1ug = 40IU)
- Rampage, Quintox, Ortho Mouse-B-gone
- Calcipotrience (donovex lotion for psoriasis)
- Potent and high risk for dogs
- Vitamin D3 supplements
- human supplements
- Vitamin D3 is 10X more potent than D2 for calcium uptake.
- Some toxic plants
- S. malacoxylon, C. diurnum, T. flavescens
Vitamin D:
Kinetics
K9 daily requirements is 22iu (0.55ug/kg/day)
Absorption - rapid and complete in small intestines
Circulates in plasma to liver and kidney
Liver: metabolized to 25-hydroxy D3
Kidney: Converted to toxic metabolites - 1,25 dihydroxy D3
D3 metabolites excreted in bile
Vitamin D:
Toxicity
Minimum lethal dose: 5mg/kg
1-3 mg/kg toxic = 2.6g bait / kg BW
Calcipotriol toxic at 50ug/kg
Cats most sentitive > puppies > Adult dogs
Vitamin D:
Mechanism
- 1.25 dihydroxy D3 in kidney
- increases serum calcium levels in 3 ways
- increasing absorption from gut
- Increase bone resorption via PTH
- Increase renal retention via distal tubule resorption
- Persistent hypercalcemia and hyperphosphatemia
- Early renal tubular damage and necrosis
- Abnormal soft tissue mineralization
Vitamin D:
Pathophysiology
- Hypercalcemia - Conduction Disturbance:
- Shortened Q-T segment aind increased P-R
- Bradycardia
- Vasoconstriction and hypertension
- Reduces cAMP → low ADH
- Renal Tubular Degeneration
- polyuria and hyposthenuria
- Azotemia
Vitamin D:
Clinical Pathology
Hypercalcemia > 12mg/dl
Hyperphophatemia >7mg/dl
Increased BUN and creatinine
Urine Specific Gravity 1.002 - 1.006 → Hyposthenuria
Vitamin D:
Clinical Picture
delayed 12-36 hours post ingestion
Progressive signs: anorexia, vomiting +/- blood, depression, muscle weakness, cardiaca and renal changes, Bradycardia, heart failure, Hypertension, polyuria, polydipsia
Vitamin D:
Lesions
Renal tubule necrosis
Soft tissue mineralization
Aortic plaques
Thyroid changes
Vitamin D:
Diagnostics
Serum calcium > 12mg/dl
Bradycardia
Azotemia
Elevated D3 metabolites: 25-hydroxy D3
Serum iPTH depressed
Tissue mineralization
Elevated Kidney Ca and P
Vitamin D:
Differentials
Hypercalcemia of Malignancy
Chronic Renal Failure
Primary Hyperparathyroidism
Feline Idiopathic Hypercalcemia
Vitamin D:
Treatment
- Recent Ingestion
- emetics, cathartics, activated charcoal ASAP and continue charcoal for 1-2 days to block recycling
- Saline Diuresis
- Furosemide
- Prednisone
- Calcitonin
- Pamidronate - IV infusion
- Calcium restriction, anti-emetics, GI protectants
Vitamin D:
Environmental and Food Safety Impact
All species susceptible
Secondary introxications can happen
Excreted in milk
Zinc/Aluminum Phosphate:
Rodenticide
Limited Use: alternative to anticoagulants, bromethalin, Vit. D
Gray-black powder
Decomposes in moist, acidic, environments (stomach)
Pungent odor (acetylene, garlic, fish)
Dogs most often poisoned
Also used as a grain fumigant
Zinc/Aluminum Phosphate:
kinetics
- Hydrolized in acidic stomach
- full stomach enhances reaction
- Zn3P2 → PH3 + Zn2
- Phosphate gas is the main toxicant
- Zinc moiety is a stong emetic
- protective in dogs
- Rats can’t vomit
