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22 Cards in this Set

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Organophosphorus Compounds

Irreversible AChE Inhibitors Therapeutic Agents
Echothiophate
Diisoprophyl
Irreversible AChE Inhibitors

Insecticides
Tetraethyl pyrophosate
Parathion
Malathion
Irreversible AChE Inhibitors

Nerve Gases
Sarin
Soman
Tabun
Irreversible AChE Inhibitors MOA
Irreversibly phophorylate (hence inactivate) AChE
If we irreversibly inactivate AChE, what effect will that have on ACh?
ACh will stay too long --> adverwe effects whih will be lethal
Diisopropyl Fluorophosphate
DFP
High lipid solubility
Volatile
Echothiophate
Positively charged
not volatile
Preferred over DFP
what are the therapeutic uses of DFP and echothiophate?
Miotic
Glaucoma
These are drugs of last resort
What is important about insecticides?
Most of organophosphates are well aborbed from the skin, gut, and conjuctiva --> dangerous to humans
Limited half life when dissolved in water
What is Parathion?
Insecticide
Not used clinically
Major problem with accidental poisoning.
What is Malathion?
Insecticide
Low dermal absorption
Detoxified by plasma carboxylesterases more rapidly in mammals and birds than in insects
Used clinically to treat head lice
What is the range of toxicity in the irreversible AChE inhibitors?
Malathion < Parathion <<<< Sarin
What are the adverse effects of AChE inhibitors?
Lens opacities (echothiophate)
Chronic neurotoxicity
Cholinergic overstimulation
Cholinergic crisis
How does triorthocresylphosphate (an additive in lubricating oils) causes chronic neurotoxicity?
Triorthocresylphosphate --> inhibits neurotoxic esterase --> axonal swelling & demylenation --> sensory disturbances, ataxia, weakness, tendon reflexes, muscle twitching, reduced tenderness
What can ACh do?
Stimulate M receptors at effector organs.
Stimulate cholinergic receptors in the CNS
Produce stimulation followed by depression or paralysis of autonomic ganglia and skeletal muscle
What is the difference between neostigmine, physostigmine, and the organophosphates?
Neo--reversible, doesn't cross BBB
Physostigmine--reversible, crosses BBB
Organophosphates--irreversible, crosses BBB
What effects will be caused by cholinergic overstimulation/crisis?
Miosis
spasm of accommodation
Extreme salivation
Sweating
Bronchoconstriction
Vomiting
Diarrhea
Bradycardia
Hypotension
Urinary urgency
What are the CNS effects of cholinergic overstimulation/crisis?
Confusion
Ataxia
Slurred speech
Loss of reflexes
Convulsions
Coma
Central respiratory paralysis
What are the skeletal muscle effects of cholinergic overstimulation/crisis?
Involuntary twitching
Severe weakness
Paralysis
What is the cause of death in the cholinergic overstimulation/crisis?
Respiratory failure and cardiovascular collapse
What is the treatment of cholinergic crisis?
Sarin --> excessive activation of M/N receptors (both central and peripheral)--> central (muscarinic blocker--atropine) and peripheral (cholinesterase reactivator--2-PAM)
What is cholinesterase reactivator?
Pralidoxime (2-PAM)
NMJ
Autonomic ganglia
peripheral effector sites
Used only for organophosphate poisoning