HERBICIDES
Chlorphenoxy compounds:
(see book for long names)
Used to control broad-leaf plants
2,4-D – does NOT contain dioxin
2,4,5-T – contains dioxin
TCDD (dioxin) – potent P-450 inducer; is also a teratogen and
carcinogen; can produce chloracne in humans
* toxic effects include: stiffness of the extremities, ataxia,
and paralysis
Dinitrophenols:
Dinitro-orthocresol
* uncouples oxidative phosphorylation
* treatment consistis of ice baths, and oxygen by mask
Bipyridyl comopunds:
Paraquat – main target is the lung, irrespective of route of
Exposure; toxic effects are due to formation of a
Superoxide anion radical
Treatment involves removal before absorption by gastric
lavage or cathartics; after absorption hemodialysis or
hemoperfusion might be necessary.
FUNGICIDES
Compounds include:
Dithiocarbamates
Mercurials
Hexachlorobenzene
Pentachlorophenol
Dithiocarbamates:
Acute toxicity is low
Ethylenebisdithiocarbamate is metabolized to a known
thyroid carcinogen (ethylenethiourea)
Also has antithyroid action,and produces a disulfiram-like
response to alcohol!
Mercurials:
See the Mercury section of the heavy metals for toxicities
Hexachlorobenzene:
Is a P-450 inducer, a carcinogen and a teratogen
No longer in use in the US
Produces liver injury and ‘porphyria cutanea tarda’
Neurologic effects include irritability and tremors
Pentachlorophenol:
Is an uncoupler of oxidative phosphorylation…can be fatal
Cases where this has been used in diapers have led to
fatalities!
Commercial products have dibenzodioxins and
dibenzofurans, but not TCDD
Penicillamine:
Well absorbed from the GI tract
Particularly useful in the treatment of Wilson’s disease
Causes a maculopapular or erythematous rash with
generalized edema, pruritis, and fever
Cross-sensitivity to penicillins may exist!
OTHER USEFUL INFORMATION
Deferoxamine:
Poorly absorbed orally
Causes a number of allergic reactions including: pruritis,
wheals, rash, and anaphylaxis
Methemoglobin forming chemicals
Direct:
Nitrites
Indirect:
p-aminophenol
Analine
Nitrobenzene
p-aminopropiophenone
Pharmacokinetics, etc.. of Chelators
EDTA:
This is actually a calcium and sodium salt of EDTA
Less than 5% is absorbed from GI, so it is usually given
IV or occasionally IM
It is water soluble, and does NOT enter into cells
T1/2 is about 20-60 minutes
Excreted unchanged in the urine
Is toxic to the kidney; results in proximal tubular injury, but
is usually reversible; will cause pain at injection site
Dimercaprol (BAL):
Used in combination with EDTA
Is administered in oil by deep IM injection
More readily enters tissues than does EDTA
Can cause N/V, headache, and a burning sensation of
the lips
Increased BP, and tachycardia are also seen
Production of an alkaline urine will protect the kidney from
the toxic effects of most chelators!
Succimer:
Similar to BAL, chemically
It is effective orally; used to treat children w/ lead levels
greater than 45g/dL
Most common effects are GI: N/V, diarrhea, and loss of
appetite; rashes and elevation of liver enzymes have
been noted