Pharm is so broad, and there's really tons to cover, but in terms of a little:
It's HUGELY high-yield (I've encountered a few practice questions on this already) that macrolides (azithromycin) are given to patients with Strep infections who can't tolerate penicillins.
The only reason you don't give aztreonam is bc that's for gram(-) aerobic rods only (same as aminoglycosides [so if they also ask for the drug that's synergistic with aminoglycosides, this is the answer; they'll try to trick you with ampicillin just bc you normally give aminos with amp/amox]).
Another tidbit I've encountered: Ceftriaxone is known to complex with calcium. Given that ~40% of the drug is excreted through bile, it is specifically known to cause pseudolithiasis, which abates upon cessation of the drug.
For vancomycin, know that that's MRSA, but it's also ENTEROCOCCI. If you get VRE, however, use streptogramins (dalfopristin/quinupristin).
If a patient being treated for MRSA gets Sx of pseudomembranous colitis, the drug used was clindamycin. I've also encountered this in a practice question. Clindamycin and TMP-SMX can also be used to Tx MRSA, but, in general, vancomycin is top choice.
Another thing: Doxycycline is used to treat all Rickettsial infections. That means use it for epidemic/endemic/scrub typhus, RMSF. Also (super-high-yield), it's always used for Lyme disease. Also use it for Ehrlichia chaffeensis. They'll try to trick you by saying the guy's had a tick bite and rash, but then they'll throw in that he has "aggregates of organisms within macrophages," which, if you remember from FA, "berry cluster" organisms is Ehrlichiosis, so don't get tricked. However, unlike Lyme disease, where you always have ECM, you may not have any rash for Ehrlichiosis, but if it does appear, it's truncal. But yeah --> doxycycline for that too.
Okay, so as far as gonococcus vs meningococcus is concerned, ceftriaxone is always the treatment. However, here's where it gets tricky: rifampin is the prophylaxis for meningococcal infections (and H. influenzae); fluoroquinolones are the prophylaxis for gonococcal infections.
Fluoroquinolones are also the 1st-line Tx for Shigella and are the drug of choice for UTIs if the pt has a sulfa allergy.
Although FA mentions that tetracyclines can't be consumed with divalent cations (e.g. antacids) due to deficient absorption, this also applies to fluoroquinolones (I've encountered this in a practice question).
There's seriously so much to talk about. If you have any specific questions just let me know.
