Denise has been suffering from depression, for which a physician prescribed an M

Question

Denise has been suffering from depression, for which a physician prescribed an MAO inhibitor. She didn't reveal to him that she frequently used cocaine, or that a different doctor had prescribed Xanax to reduce her anxiety and help her sleep. Wanting to treat herself, she decided to go to a fine restaurant that she chose because they claimed to serve only organic produce not treated with pesticides. She congratulated herself on avoiding cheese dishes and treated herself to an appetizer of fresh mussels. However, partway through the dinner she suffered a seizure. Paramedics arrived and were able to control her seizure with intravenous benzodiazepine. When Denise recovered, she angrily accused the restaurant manager of serving her contaminated mussels, which he vehemently denied.

Some of the new terms and concepts you will encounter include:

Saxitoxin and voltage-gated channels

Acetylcholinesterase and cholinesterase inhibitors

Monoamine oxidase and MAO inhibitors; GABA and benzodiazepines

Denise had a seizure after eating fresh mussels at the restaurant.

If the mussels were contaminated with saxitoxin, how would they have obtained it?

If the mussels contained saxitoxin, are the symptoms it produces compatible with the symptoms that Denise displayed?

Denise was careful to eat only produce that did not contain pesticides.

If it had organophosphate pesticides, what danger might that present?

Is it likely that pesticides on her restaurant's vegetables would have produced her symptoms?

Denise had a prescription for an MAO inhibitor to treat her depression. She carefully avoided dishes with cheese.

What is the action of MAO inhibitors and how do they affect depression?

What does cheese contain that could be dangerous to Denise, and how would it be dangerous?

Denise frequently used cocaine.

What is the mechanism of cocaine action on the nervous system?

How might her use of cocaine have led to her seizure at the restaurant?

Denise had a prescription for Xanax to treat her anxiety and help her sleep.

What is the mechanism of action of Xanax and other benzodiazepines?

How would the benzodiazepines be beneficial in treating Denise's seizure?

Explanation / Answer

1) MAO inhibitors are of two types -

MAO- A = acts on all catecholamines

MAO- B = acts only on dopamine

MAO catabolizes the catecholamines.

They improve depression by increasing serotonin level in the CNS.

2) Cocaine inhibits the reuptake of noradrenaline and other catecholamines hence making it available for the post synaptic receptors for longer time.

3) The use of cocaine leads to her seizure because it acts as sympathomimetic drug, and she is already on MAO inhibitor, which leads to tremendous increase in the level of dopamine in the CNS.

4) Benzodiazepines and Xanax acts via GABA - A receptors. On the activation of these receptors chloride ion moves within the cell and lowers the testing membrane potential of neuron, hence making it difficult to excite.

5) Benzodiazepines is useful in treating seizure because it makes the nerve difficult to excite. In seizure there occurs overexcitation of neurons.

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