Malathion Is Hydrolyzed by Plasma Carboxylases in Birds and Mammals but Not Insects 1

Preferentially hydrolyzes aliphatic esters Malathion is a substrate Carboxyl Esterases Preferentially hydrolyzes aliphatic esters Malathion is a substrate Are inhibited by organophosphates May also be called aliesterases 2

0.5% solution in 78% isopropranolol is pediculicidal and ovicidal 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 3

Rapidly metabolized by birds and mammals 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 4

P-F bond P-CN bond Phosphoester bond Anhydride bond Aryl Esterases Are found in the plasma and liver Hydrolyzes organophosphates at the P-F bond P-CN bond Phosphoester bond Anhydride bond 5

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 6

NERVE AGENT VX Chemical name: O-ETHYL-S-(2-DIISOPROPYLAMINOMETHYL)METHYL-PHOSHONOTHIOLATE Trade name: PHOSPHONOTHIOIC ACID NERVE AGENT VX

NERVE AGENT VX Chemical name: O-ETHYL-S-(2-DIISOPROPYLAMINOMETHYL)METHYL-PHOSHONOTHIOLATE 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. 9

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. 10