Toxic Dose Calculation Flashcards
What are the 4 basic tenets of toxicology?
- the dose makes the poison
- exposure does not equal poisoning
- for most toxicants, there is a dose-response relationship and a threshold dose
- many factors influence toxicity
What does “the dose makes the poison” mean?
- virtually all substances are toxic if given at a high enough dose
- virtually all substances can be safe if given at a low enough dose
What must occur for an agent to cause a toxic effect?
must reach its site of action at a high enough concentration and for a sufficient time —> this is why treatment includes decontamination —> can get rid of agent after exposure, but before it causes toxicosis
What is a threshold dose?
highest dose at which there is no response
- toxicosis = dose higher than threshold
What factors influence toxicity?
- characteristics of the animal exposed: age, species, strain, sex, nutritional status, pre-existing conditions, reproductive status, medication history, exposure to other toxicants
- characteristics of toxicant: formulation, concentration, kind of toxicant
- route of exposure
- frequency and duration of exposure
- environmental status: snakes more common in warm places
Why do we calculate dosage?
(amount of toxicant/BW) —> dose = total toxicant exposed
decides how to proceed with a case
- Is the exposure going to cause adverse effects?
- What clinical signs may develop?
- Is any treatment needed?
- What decontamination should be performed?
- Should the patient be hospitalized for monitoring?
- Is there an antidote?
- What are the likely costs of treatment?
Why do we not just treat any exposure to a toxicant?
risks (and expenses) of treatment may outweigh risks of poisoning
How is a treatment regimen for a potential toxicosis decided upon?
severity of poisoning
- aggressive treatment for lethal exposure
- risk from poison must outweigh risk of treatment with sublethal doses
What is necessary for diagnosis of toxicoses?
history
- What toxicant was exposed to the animal?
- What is the active ingredient?
- What is the toxicity of the active ingredient?
- Is the amount of ingested active ingredient of concern?
- Should it be treated?
Why is diagnosis of toxicoses hard to arrive at?
exposure is usually not witnessed - animal presents with sudden illness and other possibilities must be ruled out
What is important to consider?
What kind of chocolate did Tusia ingest?
- different types have different concentrations of theobromine
- solid milk chocolate
How much chocolate was ingested?
- 10 to 20 eggs (always choose worst case scenario!)
- size/weight —> 9 kisses weigh 41 g
Did she eat enough to cause poisoning?
Tusia’s owner believes she ate 10-20 eggs. How much chocolate did Tusia ingest? Theobromine and caffeine?
Hershey’s website states that 9 kisses weigh 41 grams and contains 61 mg of theobromine and 9 mg of caffeine.
Tusia’s owner believes she ate 10-20 eggs. How much theobromine and caffeine was Tusia exposed to in ounces? What was the dosage of total methylxanthines?
Hershey’s website states that 9 kisses weigh 41 grams and contains 61 mg of theobromine and 9 mg of caffeine.
(41g/9 kisses) = 4.55 g/kiss
20 kisses x (4.55 g/kiss) = 91 g milk chocolate
When is treatment for toxicoses indicated?
when exposure dose/dosage is greater than the MTD
Owner states that the puppy ate three 3-oz throw bags. How much bait did the puppy eat?
The active ingredient in the bait is diphacinone and makes up 0.005% content. How much diphacinone did the puppy eat?
If the puppy weighs 20 punds, how many mg of diphacinone per kg of body weight did the puppy ingest?
3 oz x (28g/oz) = 84 g per pack
3 packs x (84g/pack) = 252 g bait
20lb/2.2 = 9 kg
(12.6mg)/(9kg) = 1.4 mg/kg (dosage)
33lb/2.2 = 15 kg
15 kg x (5.5mL/kg) = 82.5 mL of 20% solution per dose
