CHAPTER 13 – OVERVIEW OF THE SOMATIC NERVOUS SYSTEM AND THE DRUGS AFFECTING NEUROMUSCULAR TRANSMISSION

Question 1

Andrew, a 30-year-old market gardener, recently sprayed his crops with an organophosphate pesticide. Although Andrew took all precautions a strong wind developed while he was spraying and he inhaled a high concentration of the pesticide. On returning home he complains to his wife of headache, dizziness and tremor.

Answer 1

Andrew, a 30-year-old market gardener, recently sprayed his crops with an organophosphate pesticide. Although Andrew took all precautions a strong wind developed while he was spraying and he inhaled a high concentration of the pesticide. On returning home he complains to his wife of headache, dizziness and tremor.

Question 2

Explain why Andrew has developed these symptoms

Answer 2

The organophosphate pesticides inhibit AchE by forming a very stable complex principally with esteratic site. Toxicity occurs as a result of irreversible inactivation of AchE leading to an accumulation of acetylcholine

Question 3

Later that evening his wife notices that he is confused, appears to be crying, is salivating profusely and can’t remember where he is. She immediately calls an ambulance, which arrives within 10 minutes.

Answer 3

Later that evening his wife notices that he is confused, appears to be crying, is salivating profusely and can’t remember where he is. She immediately calls an ambulance, which arrives within 10 minutes.

Question 4

Explain why Andrew’s condition has further deteriorated

Answer 4

Persistant stimulation by ACh at pre synaptic and postsynaptic receptors occurs initially, followed by paralysis of cholinergic neurotransmission. Ultimately effecting the somatic, autonomic and CNS

Question 5

The paramedics assess his condition and determine he has significant organophosphate exposure. The administer atropine (1mg) and transport him immediately to the nearest hospital emergency department, which is 2km away.

Answer 5

The paramedics assess his condition and determine he has significant organophosphate exposure. The administer atropine (1mg) and transport him immediately to the nearest hospital emergency department, which is 2km away.

Question 6

Explain why the paramedics have administered atropine.

Answer 6

Atropine antagonises the muscarinic effects of excess acetylcholine but is ineffective in antagonising the nicotinic effects of acetylcholine and hence muscle weakness and paralysis does not improve, and pralidoxime.