Transcript Malathion Is Hydrolyzed by Plasma Carboxylases in Birds and

Malathion Is Hydrolyzed by Plasma Carboxylases in Birds and Mammals but
Not Insects
Carboxyl Esterases

Preferentially hydrolyzes aliphatic esters

Malathion is a substrate

Are inhibited by organophosphates

May also be called aliesterases
R(CH2)CO-OR'
Uses of Malathion

Insecticide

Therapeutics
 Used as a lotion for Pediculus humanus capitis
associated with pediculosis



0.5% solution in 78% isopropranolol is pediculicidal and
ovicidal
Ovide is the brand name
Primoderm was the former brand name
Malathion Metabolism

Rapidly metabolized by birds and mammals

Plasma carboxylases are involved

Insects do not possess the enzyme

Organophosphates inhibit malathion metabolism

Malathion is toxic to fish
Aryl Esterases

Are found in the plasma and liver

Hydrolyzes organophosphates at the

P-F bond



P-CN bond
Phosphoester bond
Anhydride bond
EPA And Organophosphates

Diazinon
 No longer allowed to be manufactured for
indoor use in as of March 1, 2001 or for garden
use as of June 3, 2001
 Found in Real Kill®, Ortho®, Spectracide®
 Limited agricultural use is allowed

Chlorpyrifos (Dursban) has been phased out

Parathion has been phased out for agricultural use
in the United States
Chemical name:
O-ETHYL-S-(2-DIISOPROPYLAMINOMETHYL)METHYLPHOSHONOTHIOLATE
Trade name: PHOSPHONOTHIOIC ACID
NERVE AGENT VX
NERVE AGENT VX
Chemical name:
O-ETHYL-S-(2-DIISOPROPYLAMINOMETHYL)METHYLPHOSHONOTHIOLATE
Trade name: PHOSPHONOTHIOIC ACID
Organophosphates as Nerve Gas Agents
in Chemical Warfare (1)

Extremely volatile agents such as sarin, tabun, soman,
and agent VX may be used as nerve agents in chemical
warfare.

Accumulation of ACh at cholinergic receptors produces
effects reflecting stimulation of cardiac muscle, smooth
muscles and glands. Such effects would be identical to
those caused by muscarine poisoning.

Bradycardia and hypotension occur. However, in some
cases, tachycardia may be observed, due to intense
sympathetic discharge in response severe hypoxemia.
Organophosphates as Nerve Gas Agents
in Chemical Warfare (2)

Irreversible inhibition of acetylcholinesterase by these agents
produces accumulation of ACh at the end plate of skeletal
muscle fibers. This in turn leads to depolarizing blockade of
the NM nicotinic receptor. Skeletal muscle paralysis occurs.
Movement is impossible. The diaphragm is also paralyzed.
The individual eventually dies due to respiratory paralysis.

Pralidoxime, atropine, and removal of the person from the
source of exposure are all to be employed in cases of
posioning.