topic 24

Question 1

What can happen when multiple tablets are ingested at the same time? What is a dangerous example of this?

Answer 1

Adherent masses of tablets “concretions”

Reduced surface area for dissolution

Prolonged absorption from huge drug
reservoir

Beware aspirin, meprobamate

Question 2

What can anticholinergic or narcotic drugs do to adsorption?

Answer 2

 Agents with anticholinergic or narcotic
effect may slow GI motility

Unabsorbed drug trapped in quiet gut

When gut recovers, absorption resumes

Patient relapses; cyclic effect

Question 3

What are some drugs that typically display michaelis menten kinetics? Why are MM patterns more common at higher doses? What is the result?

Answer 3

 Saturation kinetics are unusual clinically
because doses are so small

 BUT, metabolism of higher doses may exhibit
a saturation point

 Common agents with MM at typical doses:
ethanol, aspirin, phenytoin

 Slower decline of blood concentrations

 Don’t count on a known “half-life” derived
from therapeutic dosing

Question 4

What are 5 therapeutic interventions used to augment clearance?

Answer 4

 Therapeutic interventions used to
increase the clearance

v Adsorption to activated charcoal

v Chelation

v Specific antibody fragments

v Enhanced endogenous clearance

v Extracorporeal removal

Question 5

What are 2 things that can be done to enhance endogenous clearance via the kidney? What are two things that shouldn’t be done? What can they be used to clear?

Answer 5

Use adequate or robust hydration to maintain renal bloodflow and glomerular filtration.

Use the concept of ion trapping for acids such as salicylic acid or 2-4-D by alkalinizing urine using IV sodium bicarb which will cause the toxin to be more unionized in tubule cells making it more likely to be excreted.

Don’t force Diuresis!

Don’t acidify urine to help excrete weakly basic toxins. Its dangerous.

Question 6

What are 3 types of extracorporeal removal? How does the concept work in general?

Answer 6

 Blood is diverted through an apparatus
which removes toxin & returns blood to circulation

• Hemodialysis (most common, still rare)
• Hemoperfusion
• Hemofiltration

Question 7

How common is hemodialysis used for poison patients? What are five toxins that its indicated for?

Answer 7

 HD benefits only a small percentage of
poisoned patients

 Considered for poisoning by

• Methanol
• Ethylene glycol
• Lithium
• Theophylline
• Salicylates

Question 8

Why is hemodialysis normally not used? what are some clinical indications of when it should be used? What are some characteristics of dialyzable toxins?

Answer 8

Most of time it is not necessary
Endogenous clearance adequate

 Consider use in patients who have renally-excreted toxin but inadequaterenal clearance
 Used in any setting for which it would
normally be indicated, poison or not
 Patient with potentially life-threatening
toxin load and severe symptoms unresponsive
 Patient is able to withstand significant
cardiovascular stress
 Toxin must be subject to removal by
this technique:

Molecular weight < 500 daltons
High water solubility
Low protein binding
less important in large dose poisoning
Low volume of distribution

Question 9

How do we get lead in our bodies? Deficiency in what 3 elements increases lead absorption?

Answer 9

Paint in houses earlier than 1970, lead laden dust

 Pb absorption increased by co-existing deficiency of Fe, Ca, Zn

Question 10

What ares some symptoms of lead poisoning? Are they early or chronic symptoms?

Answer 10

GI Symptoms:

 Early signs: vomiting, colicky abdominal pain, constipation
 More chronic: Gingival lead lines

In CNS:

 Chronic, children: developmental
impairment of IQ, hearing, growth, behavior
 Chronic, adults: peripheral motor neuropathy such as wrist drop

 Dense transverse metaphyseal bands (more dense than cortical bone) (chronic)
 Most prominent at knees, also in wrist, any other
long bone metaphysis, and in the axial skeleton

Question 11

What is 3 antidotes for lead How does each work? When is each indicated? What are some adverse effects?

Answer 11

Calcium disodium Ethylene Diamine
Tetra Acetic acid (EDTA)
Chelates lead
 Can be used alone unless encephalopathy
or blood lead ≥70 mcg/dL:
 Combined dimercaprol (BAL) plus EDTA used together to prevent mobilization of lead into CNS
 Adverse effects: renal tubular toxicity &
removal of essential metals such as zinc & iron

Succimer, DMSA Dimercaptosuccinic acid
Water soluble, “heavy metal” chelator
 Treat childhood lead poisoning for blood
lead concentrations 45-69 mcg/dL
Also for arsenic, mercury & other metals
Better safety profile than the lipid soluble chelators such as CaNa2 EDTA, BAL, or water soluble penicillamine

Question 12

What is arsenic? What does it react with? How do people get contaminated? What are some uses and sources?

Answer 12

 Arsenic is a metalloid
 Forms compounds with metals and C, N, O
 Either oxidized or reduced in chemical reactions

 Natural contamination of well water

 Local airborne contamination by burning high-
arsenic coal

 Dopant in silicon chip & semiconductor manufacture, as gallium arsenide or arsine gas
 Wood preservative “CCA’ (chromium, copper,
arsenic)
 No longer permitted by EPA for residential use
 Pesticides (insecticides, fungicides, herbicides)
 Homepathic & traditional-cultural medicines
 AsO3 salvage therapy for acute promyelocytic leukemia

Question 13

What type of arsenic is most dangerous? What is the early course of arsenic poisoning manifest like?

Answer 13

 Trivalent arsenic is more toxic than
pentavalent
 Organic arsenic (shellfish) relatively non-toxic.

 Acute poisoning:
• Severe gastroenteritis including projectile vomiting, profuse “rice water” diarrhea, excruciating abdominal pain
Sudden drop in blood pressure, and encephalopathy

Question 14

What is the antidote for early course arsenic poisoning? How does it work? What else is it used to treat? What should it not be used for? What are its adverse effects?

Answer 14

ANTIDOTE: BAL (British Anti-Lewisite):2,3 dimercaprol

 Di-thiol chelator binds arsenic into a stable complex & augments renal excretion
 For arsenic, mercury, gold
 For lead (only plus EDTA if…)
 Do not use for iron, cadmium or selenium

 Peanut oil suspension given IM (intra-
muscularly) and not IV (intravenously)
 Transient hypertension and tachycardia
 Fever
Pain at the injection site
 Nausea and vomiting
 CNS: headache, tremor, apprehension, fatigue, weakness
 Lacrimation and rhinorrhea

Question 15

What does the later course of acute arsenic poisoning look like?

Answer 15

Damage to multiple organs
 Cardiomyopathy
 Rhabdomyolysis
 Renal failure
 Hepatic injury
 Bone marrow depression of all cell lines

Delayed sequelae (if patient survives)
Sensory-motor neuropathy
Skin eruptions, alopecia, and Mee’s lines

Question 16

What happens with chronic arsenic poisoning?

Answer 16

 Weakness, malaise, anorexia, other GI
 Mild encephalopathy
 Tremors, ataxia, incoordination, confusion
 Peripheral neuropathy
 Painful paresthesias, muscle weakness & pain
 Hyperpigmentation, palmar- plantar hyperkeratosis, peripheral edema
 Skin cancer, also lung and bladder cancer

Question 17

What are 3 different forms of mercury? Where are they found?

Answer 17

 Complex toxicology…various forms… different toxic profiles

 Elemental liquid mercury, Hg0
 Thermometers, control devices, dental
amalgam

 Inorganic mercury, such as HgCl2
 Disinfectant, tannery, chemical synthesis

 Organic mercury, such as CH3Hg
 Fungicide manufacturing, embalming,
chemical synthesis

Question 18

How does exposure to elemental mercury occur? How does acute exposure manifest? Chronic?

Answer 18

Inhalation hazard

Acute, high exposure … pneumonitis

Chronic exposure… renal impairment, gingivitis/ stomatitis/ ptyalism, “erethism”
• Neuropsychiatric abnormalities: personality changes such as shyness, withdrawal, excitability
• Insomnia, headache, memory loss, ataxia, altered taste & smell, anorexia, weight loss

Question 19

What causes acrodynia? How does it manifest?

Answer 19

Due to Chronic mercury exposure

 Bright pink, painful, palmar-plantar, desquamating rash

 Classic presentation mercurial teething & diaper powders

 Painful peripheral neuropathy: diaphoresis, hypertension, fine tremors, weakness, irritability,
insomnia, anorexia

 High serum catecholamines

 Hypersensitivity reaction?

Question 20

What happens with the ingestion of each three types of mercury?

Answer 20

 Acute ingestion of elemental mercury
 Non-toxic in most situations

 Acute ingestion of inorganic mercuric salts
 GIT corrosion, shock, acute renal failure

 Chronic ingestion organic mercury
 Severe central nervous system impairment

Question 21

How is/was thallium used? How does thallium poisoning manifest?

Answer 21

 Former rodenticide; still has application as industrial chemical, homeopathic remedy, homicidal agent

1. Severe gastroenteritis
2. Delayed neuropathy (sensorimotor)
3. Alopecia in the second week – Complete baldness is characteristic

Question 22

What is the antidote for thallium poisoning? What else is it used for? How does it work?

Answer 22

Prussian Blue

 Pigment …treats overexposure to thallium
and radioactive cesium (dirty bomb)

 Tl or Cs excreted into the bile, reabsorbed
in the gut and returned to the liver, which excretes them again in the bile……

 Oral Prussian Blue traps Tl or Cs in the gut, prevents re-absorption from the intestine and thereby increases fecal excretion
Reduces halflife

Question 23

What are some examples of organophosphates?

Answer 23

Organophosphate compounds: Insecticides such as malathion & diazinon

Nerve agents sarin, soman, tabun, VX

Question 24

What are the effects of organo phosphates? How do they work? How are they absorbed?

Answer 24

 Inhibit acetylcholinesterase

 “Age” on the enzyme, permanent deactivation

 Poisoning involves all cholinergic receptors

 Muscarinic: DUMBELS

 Nicotinic: excitation then fatigue of ganglia and
excitation then fatigue of skeletal muscle

 CNS: coma, seizures, central resp depression

 Easily absorbed through skin; risk of 2°

contamination to rescuers

Question 25

What are two antidotes for organophosphate poisoning? How do they work? What do they do? How do you know if they’re working? When should each be used?

Answer 25

Atropine:
 Treats muscarinic effects of cholinesterase inhibition (not nicotinic or CNS) as from OP & carbamate insecticides, “nerve agents, ” donepezil, muscarine-mushrooms, others
 Very high doses of atropine may be needed
 End point is dry respiratory secretions/ airway control

Pralodoxime:
 Consider for severe poisoning only, not routine in all cases (atropine always!)
 Reverses organophosphate (OP) agent effects on the neuromuscular junction (fasciculations, weakness) by reactivating inhibited acetylcholinesterase
 Combines with OP-AChEsterase complex
De-phosphorylates the site before it AGES
Restores its ability to degrade acetylcholine