(c) reworded version of the above

(c) Answer is (c)- (a), (b) and (d) are all used orally. Penicillin G is destroyed by acid in the stomach resulting in variable and irregular absorption. Penicillin V is acid stable and available for oral use. Penicillin G procaine is typically given intramuscularly in repository form, yielding a tissue depot from which the drug is absorbed over hours. In this form, it cannot be given IV or subcutaneously.

(c) again, just asking you to know something about the various forms of penicillin. Since in most cases you are going to use Pen VK orally, this question is an old one showing its age and probably not likely to appear anymore on board excams

(a) ampicillin sort of sounds like penicillin so it must be the answer

(b) This is a memorization question, with (b) the correct answer. You have to remember that the cephalosporins (like cephalexin) are chemically related to the penicillins. The others are not chemically related and thus cross-allergenicity is unlikely

(b) just slightly reworded version of the above question, but with some different alternatives thrown in. Obviously, if you can recognize whther or not a drug is a penicillin or a cephalosporin , and you remember that these are the classes that show crossallergenicity, then you can handle any rewording of this question.

(c) see above

(b) all of the other methods involve unacceptable risk. Once sensitized, even a small amount can cause an allergic response. Remember, it is not a dose-related response that won’t be problematic if you only inject a little bit.

(b) boy, if you haven’t heard this a zillion times by now.. None of the alternatives listed would be a problem in terms of crossallergenicity, but the reason (b) is the right answer is that the spectrum of activity of erthromycin is very similar to penicillin. The others offer a much broader spectrum of coverage than we usually require; always use the drug with the narrowest spectrum possible that includes the microbe in question. Standards have now changed such that clindamycin is the drug of choice in this situation. But if they don’t include clindamycin, look for erythromycin, or for that matter Azithromycin

(b) that’s why it is considered an “extended-spectrum” form of penicillin

(e) that’s really the only use for dicloxacillin

(b) of those listed only (b) is penicillinase resistant. Ampicillin is an extended spectrum penicillin, and is not penicillinase resistant. Erythromycin shouldn’t be affected by penicillinases, since it isn’t a peniciilin, but it doesn’t work against staph for other reasons.

(e) Wow, I bet you didn’t think they would ask something like this!. An extended spectrum agent is required. Ampicillin is ineffective, while Pen-V is too narrow in spectrum.

(b) memorize, memorize

(c) that’s why it is selectively toxic. Wouldn’t you like it if your doctor prescribed a drug for you that did (d)?

(e) memorize

(d) same as above worded differently

(c) that’s why it is very useful for treating bone infections such as osteomyelitis. The question might have substituted gingival fluid for bone – that would make the answer tetracycline

(e) tetracycline is bacteriostatic and would slow the rapid growth of the microbial population that a bactericidal drug such as penicillin needs to be effective, sine only when rapidly dividing are the cells making cell walls

(d) the classic cidal- static interaction! See above, since this is just a reworded version of the same fact

(c) (a) streptomycin can damage the eighth nerve, affecting both balance and hearing, but is not associated with liver damage. (b) other than allergic reactions, penicillins are extremely safe, with no effect on the liver. (d) the
cephalosporins are chemically related to the penicillins and share their relatively nontoxic nature. (e) amphotericin B, is an antifungal agent that produces such adverse side effects as nephrotoxicity and hypokalemia, but not liver toxicity. Thus (c) is the correct answer. Tetracyclines have been shown to be hepatotoxic following high doses in pregnant patients with a history of renal disease.

(c) superinfections are usually seen following the use of broad spectrum agents. Of those listed, all are wide spectrum except Pen-G

(c) The only 2 possibilities that produce GI upset are (c) and (e). As for producing colitis, (b) and (c) are associated with this adverse side effect. (c) is the only drug which does both, therefore it’s the right answer.

(e) memorize

(c) memorize

(a) memorize

(b) clindamycin is the current recommendation. Erythromycin used to be, so if you get a question that doesn’t include clindamycin as an answer, look for erythromycin. Cephalexin might be a choice, but there is the issue of cross-allergencicity, and it must certainly be avoided in the anaphylactic patient. Amoxicillin and ampicillin are penicillins!

(c) always think used for herpes as the first answer

(d) broad spectrum vs. narrow spectrum. Tetracyclines certainly have more side effects than penicillin, and are certainly one of the antibiotics to avoid during pregnancy.

(d) Answer is (d)- remember, tetracyclines are broad spectrum antibiotics effective against both gram-negative and grampositive cocci and bacilli. Clindamycin has a spectrum of activity similar to erthyromycin and vancomycin, which is less than that of the tetracylines, mainly affecting gram-positive microorganisms. Ist generation cephalosporins are effective against both gram-negative and gram-positive organisms, but the third generation ones have increased activity against gramnegative but greatly decreased activity against gram-positive microorganisms.

(c) if it can’t do this it isn’t going to be very effective.

(b) Nystatin is the prototypic antifungal agent, thus (b) is the most obvious 1st choice, and eliminates (a). (d) & (e) require an antibiotic, not an antifungal

Answer is (e)- Again, the important phrase in the question is not (Hey, just Wayne and Garth). Obviously the fact that you will remember about tetracylines is that they can discolor teeth in the fetus when taken by the mother during pregnancy. But don’t circle that answer because (a) is also characteristic of tetracyclines (they are the most likely of all the antibiotics to cause superinfection), and is an annoying side effect in adults resulting from alteration of the oral, gastric and intestinal flora. The real answer is (e). Tetracyclines are not the drug of choice for prophylaxis against infective endocarditis. This is due to streptococcal infection. 15-20% of group A streptococci are resistant to tetracyclines, but none are resistant to penicillin or erythromycin. Recently a non-streptococcal induced subacute bacterial endocarditis has been identified, especially in juvenile periodontitis patients. The causative bacterium is not susceptible to penicillin or erythromycin. It may be necessary to treat predisposed patients with tetracycline for a few weeks, and then follow this with a course of penicillin or erythromycin. Remember that these drugs are antagonistic to each other and thus can’t be used concurrently. Penicillin is a bactericidal drug which kills or destroys microorganisms by interfering with the synthesis or function of the cell wall, cell membrane or both. Thus it is most effective against bacteria that are multiplying. Tetracycline is a bacteriostatic antibiotic that acts by inhibiting the growth and multiplication of organisms by inhibiting protein synthesis by binding reversibly to the 30 S subunit of the bacterial ribosome. When the two types are given together, their effectiveness is negated or reduced.

Answer is (d)- penicillin is metabolized in the liver, but it rapidly disappears from the blood due to rapid clearance by the kidneys. 90% is excreted by tubular secretion. Thus patients with renal disease will show high blood levels of penicillin. Similarly, probenicid, a uricosuric agent (a drug which tends to enhance the excretion of uric acid by reducing renal tubular transport mechanisms), reduces the renal clearance of penicillins. And you wondered why we had those lectures on pharmacokinetics!

(b) remember the famous erythromycin – Seldane potentially lethal interaction, whereby erythromycin blocks the metabolism of Seldane to its antihistamine metabolite – it stays unmetabolized and causes cardiac arrhythmias. Of course this question could have many other options listed, since erythromycin decreases the metabolism of so many other useful drugs, such as digoxin.