1.Neostigmine and bethanechol in moderate doses have significantly different effects on which one of the following?
Because neostigmine acts on the enzyme cholinesterase, which is present at all cholinergic synapses, this drug increases acetylcholine effects at nicotinic junctions as well as muscarinic ones. Bethanechol, on the other hand, is a direct-acting agent that
2. Parathion has which one of the following characteristics?
(A) It is inactivated by conversion to paraoxon (B) It is less toxic to humans than malathion (C) It is more persistent in the environment than DDT (D) It is poorly absorbed through skin and lun
The "-thion" organophosphates (those containing the P�S bond) are activated, not inactivated, by conversion to "-oxon" (P�O) derivatives. They are
than halogenated hydrocarbon insecticides of the DDT type; therefore, they are less persistent i
3. Which of the following is the best drug for distinguishing between myasthenic crisis (insufficient therapy) and cholinergic crisis (excessive therapy)?
(A) Atropine (B) Edrophonium (C) Physostigmine (D) Pralidoxime (E) Pyridostigmine
Any of the cholinesterase inhibitors would effectively correct myasthenic crisis. However, because cholinergic crisis (if that is what is causing the symptoms) would be worsened by a cholinomimetic, we choose the shortest-acting cholinesterase inhibitor,
4. A crop duster pilot has been accidentally exposed to a high concentration of a highly toxic agricultural organophosphate insecticide. If untreated, the cause of death from such exposure would probably be
, from neuromuscular paralysis or CNS depression, is the most important cause of acute deaths in cholinesterase inhibitor toxicity.
5. Pyridostigmine and neostigmine may cause which one of the following?
(A) Bronchodilation (B) Cycloplegia (C) Diarrhea (D) Irreversible inhibition of acetylcholinesterase (E) Reduced gastric acid secretion
Cholinesterase inhibition is typically associated with increased (never decreased) bowel activity. (Fortunately, many patients become tolerant to this effect.)
Answer is C
6. Parasympathetic nerve stimulation and a slow infusion of bethanechol will each: (A) Cause ganglion cell depolarization (B) Cause skeletal muscle end plate depolarization (C) Cause vasodilation (D) Increase bladder tone (E) Increase heart rate
Choice (E) is not correct because the vagus slows the heart. Parasympathetic nerve stimulation does not cause vasodilation (most vessels do not receive parasympathetic innervation), so choice (C) is incorrect. Ganglion cells and the end plate contain nico
7. Actions and clinical uses of muscarinic cholinoceptor agonists include which one of the following?
(A) Bronchodilation (asthma) (B) Improved aqueous humor drainage (glaucoma) (C) Decreased gastrointestinal motility (diarrhea) (D) Decreased neuromuscula
Muscarinic agonists cause accommodation and cyclospasm, the opposite of paralysis of accommodation (cycloplegia). In open-angle glaucoma, this results in increased outflow of aqueous and decreased intraocular pressure. These agents may cause bronchospasm
8. Which of the following is a direct-acting cholinomimetic that is lipid-soluble and is used to facilitate smoking cessation?
(A) Acetylcholine (B) Bethanechol (C) Neostigmine (D) Physostigmine (E) Varenicline
is a lipid-soluble partial agonist at nicotinic receptors and is used to reduce craving for tobacco in smokers.
9. A 3-year-old child is admitted after taking a drug from her parents' medicine cabinet. The signs suggest that the drug is an indirect-acting cholinomimetic with little or no CNS effect and a duration of action of about 2-4 h. Which of the following is
is the prototypical indirect-acting cholinomimetic; it is a quaternary (charged) substance with poor lipid solubility; its duration of action is about 2-4 h.
is similar but has good lipid solubility and significant CNS effects.
10. Which of the following is the primary second-messenger process in the contraction of the ciliary muscle when focusing on near objects?
(A) cAMP (cyclic adenosine monophosphate) (B) DAG (diacylglycerol) (C) Depolarizing influx of sodium ions via a chan
Cholinomimetics cause smooth muscle contraction mainly through the release of intracellular calcium. This release is triggered by an increase in IP3 acting on receptors in the endoplasmic reticulum.
Answer is D
The spectrum of toxicity 'DUMBBELSS'
Diarrhea, Urination, Miosis ,bradycardia, broncoconstrection , excitation ( CNS and SK ) , Lacrimation , Salivation and Sweating