(d) According to textbooks, local anesthetics fall into the following classes in terms of duration of action: short: procaine;
moderate: prilocaine, mepivacaine, lidocaine; long: bupivacaine, tetracaine, etidocaine. Statements (a), 3, and 4 would be true if the question was comparing mepivacaine to bupivacaine, which
are structurally similar; but the comparison is to lidocaine. The only difference that applies is duration of action ((d)), bupivacaine is longer. (b) is wrong, both are amides.
(c) ganglionic blockers, being so unspecific in their action (they would have both anticholinergic and antiadrenergic action) aren't used clinically anymore, but if you must know mecamylamine, hexamethonium, etc. are ganglionic blockers.
Curarine is a nicotinic receptor blocker that causes muscular paralysis
Edrophonium is an anticholinesterase used to treat myasthenia gravis
Succinylcholine is a depolarizing neuromuscular junction blocker
used for short term paralysis,
Gallamine is another long acting neuromuscular junction blocker for paralysis.
Remember, these paralysis producing drugs all act via nicotinic receptor at the
neuromuscular junction - some , like curare, are competitive receptor blockers, while the other class, like succinylcholine, are called depolarizing blockers - they don't themselves block the nicotinic receptor from being stimulated by curare, but stimulate the receptor so much that it depolarizes, and while in this state it cannot be stimulated by the Ach and thus paralysis results.
(3) Meprobamate, methantheline, and
chlorpromazine are drugs that may have been useful in the olden days, but would be probably replace in this type of questions by more modern equivalents.
Atropine (b), being the prototype anticholinergic drug has to be one of the answers. So option 5 has to bee incorrect, since it does not include atropine. Now only the most corrupt dentist would prescribe codeine to reduce salivation, so #4 should also be incorrect - that leaves 1, 2, or 3.
So see, you didn't even have to recognize that chlorpromazine is an antipsychotic drug. So what is meprobamate - if we can
eliminate that one then we are down to only option 3 as a possible answer.
Meprobamate happens to be an antianxiety,
skeletal muscle relaxant drug sometimes used by dentists to treat muscle spasms associated with TMD - also has use for
external sphincter spasticity! But it doesn't seem to have anticholinergic activity that is significant enough to cause significant reduction of saliva. Methantheline, in contrast, is Banthine, a synthetic version of atropine!
(c) this is an except question, don't miss that word! So looking at the list, we got the S (option d) and the L (option b) from SLUD, so we are left with (a), c, and (e) as possibles. (e) results from cholinergic stimulation of the NMJ, so that can't be it. (a) or bradycardia, can occur from too much cholinergic stimulation of the heart (that's why atropine is useful in surgery, to reverse the bradycardia that sometimes arises. So, by default, vasoconstriction is the exception we are looking for. (c) don't you just love the way they obfuscate? Why can't they just say the block the receptors, then everybody could get it right! But then, I don't even feel that any of the other alternatives should even tempt you, although it all depends on your interpretation of what "blocking" means. In my mind, blocking means a neurotransmitter has actually been released, and now you want a drug that somehow blocks its activity. Taken this way, options (a) and( e) wouldn't work, since, although they would reduce sympathetic activity, or have a "sympatholytic" action, they don't actually block a neurotransmitter. Option (b) again is a sympatholytic action, but I don't really think there any clinically relevant drugs that work this way. Option (d) they just made up to fool you, since you guys work with local anesthetics, so you might be tempted to jump at this answer. (a) epinephrine is a potent stimulator of both alpha and beta receptors. Injection of epi usually causes a rise in blood pressure due to 1) myocardial stimulation that increases ventricular contraction, 2) an increase in heart rate, and most important, 3) vasoconstriction due to alpha receptor stimulation. However, blood flow to skeletal muscles is increased due to powerful beta-2 receptor vasodilator action that is only partially counterbalanced by a vasoconstrictor action on the alpha receptors that are also present in the vascular bed. When given in the presence of an alpha blocker, beta-receptor mediated
vasodilation is more pronounced, the total peripheral resistance is decreased and the mean blood pressure falls. This decrease in blood pressure is called "epinephrine reversal". The only alpha-blocker listed is prazosin, answer (a). Atropine is a cholinergic muscarinic receptor blocker, propranolol is a betablocker, neostigmine is a cholinesterase inhibitor, and isoproterenol is a predominately beta receptor agonist.
(v) Answer is (e)- Corticosteroids are antiinflammatory drugs used topically, orally and parenterally. However, they suppress the immune system of the body. They have been known to cause peptic ulcers, as well as mask the symptoms of an ulcer, and perforation and hemorrhage may result. Thus "d" has to be in the answer, eliminating (a). Because they are immunosuppressive, they would obvious make an AIDS patient, who already has a compromised immune system, worse.
Similarly, latent tuberculosis could also be reactivated. Thus # 3 and (d) can be eliminated. Use of corticosteroids in inhalers for asthma, while advantageous in reducing the side effects resulting from systemic administration, has led to an increase in problems with Candidiasis, so "b" has to be in the answer. (e) is the only answer that meets all these requirements.
(a) Remember that Parkinsonism is a due to a deficiency of DA in the brain, and is currently treated with levodopa and carbidopa.
However, prior to these, anticholinergic drugs were the first drugs found to be somewhat effective for treatment of this disease, in that cholinergic and dopaminergic tracts interact in the brain, and thus reducing cholinergic activity via
anticholinergic drugs improves or enhances dopaminergic function, suggesting one is inhibitory to the other. Drugs with anticholinergic activity are often still the first drug tried. Antihistamine drugs such as diphenhydramine often have strong anticholinergic activity, which accounts for their effectiveness in drying nasal secretions associated with a cold. Therefore, the answer is (a). (e) is there to confuse you, but don't be. Diphenhydramine does not stimulate dopaminergic nerves in the basal ganglia. Adrenergic blockers ((c)) do see
some use in the treatment of Parkinson's, but diphenhydramine has no adrenergic blocking activity. Diphenhydramine does
have the actions given in (b) and (d), but these are not responsible for its efficacy in Parkinson's..
82. Which of the following are important criteria for the adequate clinical
evaluation of a new drug?
a. comparison with a placebo
b. evaluation of side effects
c. utilization of control groups
d. comparison with a standard drug
e. double blind experimental design
1. a, b, c, and d
2. a, b, d, and e
3. a, c, d, and e
4. b, c, and e
5. b, d and e only
6. all of the above
(b) the rule is ..04 mg of epi max in CV patients. The easiest way to
figure this one out is to remember you shouldn't give more than
2.2 carpules of xylocaine with 1:100,000 epi - your usual choice
as a local anesthetic. Two carpules is 3.6 cc. This eliminates
options (c) and (d), since they would be safe but not maximal.
Since 1:50,000 is twice as concentrated as 1:100,000, 1 cc of
1:50,000 (option (a)) is the same as 2 cc of 1:100,000 so still not
close to max, so (b) has to be the right answer. Of course, you
could have just remembered, 1:100,000 equals .01 mg per cc, so
1:50,000 equals .02 mg per cc, so (b) would equal the max of .04