CPTP: antibiotics

Question 1

Flucloxacillin?

Answer 1

Cellulitis. Gram +ve only. Good oral biovailibility, or IV Can be used for MSSA endocarditis.

Question 2

Amoxicillin?

Answer 2

CAP, UTIs, bacterial meningitis (along with Pen V). Some gram negative cover. Will cross BBB (meningitis). Rash in EBV.

Question 3

Co-amox (augmentin)?

Answer 3

Gram +ve, -ve and anaerobes. Good soft tissue penetration. C. diff, deranged LFTs.

Question 4

Tazocin?

Answer 4

Pipericillin/tazobactam. Antipseudomonal cover, anaerobes. IV only. Red flag sepsis.

Question 5

1st gen cephalosporins?

Answer 5

Cefalexin. UTIs. C. diff.

Question 6

2nd gen cephalosporins?

Answer 6

Cefuroxime. Broad gram -ve, some gram +ve. As a rule, later gen = better gram -ve, less +ve. No anaerobic cover so used with met in sepsis of unknown origin.

Question 7

3rd gen cephalosporins?

Answer 7

Ceftriaxone, cefotaxime. Used first line in bacterial meningitis, OPD cellulitis. Broad gram -ve cover.

Question 8

Carbapenams?

Answer 8

Very broad cover. Meropenam is antipseudomonal. Used in MDR infections. Others include ertapenam.

Question 9

Mechanism of all B-lactams?

Answer 9

All prevent bacterial cell wall formation by preventing cross-linking of peptidoglycan, all are bactericidal.

Question 10

Penicillin allergy?

Answer 10

If true allergy, can’t use any B-lactam. 5% allergic.

Question 11

Metronidazole?

Answer 11

Targets cytoplasm. Used for sepsis of unknown origin with cefuroxime, abscesses, anaerobes, C. diff (first line). AEs = GI upset. Reacts with alcohol.

Question 12

Macrolides?

Answer 12

Act on 50S subunit. Inhibits protein synthesis. Bactericidal at high concentrations. Good for atypicals, CAP (along with amoxicillin), chlamydia (azithromycin). Caution in liver/renal failure. Can inhibit CYP; be careful with warfarin! Can prolong QT, hepatotoxic, rash, GI upset, C. diff.

Question 13

Clindamycin?

Answer 13

Lincosamide. Acts on 50s. Anti-toxin features; can be indicated in cellutus/toxic shock syndrome. If allergic to macrolides, not necessarily allergic to clindamycin.

Question 14

Doxycycline?

Answer 14

Often used as amoxicillin substitute in those with allergies. 30S. Bacteriostatic. Protozoal cover. Also used in acne, malaria prophylaxis, syphilis, IECOPD. Caution in pregnancy, breast feeding, children under 12. SEs are hepatotoxicity, photosensitivity, GI upset.

Question 15

Gentamicin?

Answer 15

Aminoglycoside. Used in MRSA endocarditis with vancomycin, and strep viridens endocarditis with pen G. 50 and 30S. IV. +ve, -ve and antipseudomonal. Ototoxic and nephrotoxic. Caution in renal impairment and deaf. Dose as IBW as poorly distributed in fat. Contraindicated in myasthenia gravis (can precipitate crisis). Need to monitor because side effects are related to levels. Usually given along with metronidazole or pencillin because bad for anaerobes and streptococci. Avoid treatment for more than 7 days due to side effects.

Question 16

Quinolones?

Answer 16

Ciprofloxacin. Inhibits DNA gyrase. +ve, -ve and atypical cover. C. diff risk (bad in elderly). 100% oral bioavailibility. LOWERS SEIZURE THRESHOLD. Bad in children (achilles tendon rupture). Can be used for meningits prophylaxis. Can prolong QT.

Question 17

Nitrofurantoin?

Answer 17

Renally excreted. Only get levels high enough to be effective in urine. Need EGFR >60. Used for UTI. Avoid in third TM and neonates (haemolysis).

Question 18

Trimethoprim?

Answer 18

Folate inhibitor. Used in UTI. Avoid in renal failure. Avoid in first TM and if on other antifolates. Used in PCP prophylaxis along with sulfamethoxazole.

Question 19

Monitoring gentamicin?

Answer 19

Check trough levels. Just before second or third dose e.g. 24 hours after starting. Should be below 1mg.

Question 20

Monitoring vancomycin?

Answer 20

Also do trough levels. Aim for 10-15. Don’t need to monitor if taking orally for C. diff as no absorption

Question 21

Vancomycin?

Answer 21

A glycopeptide, like teicoplanin. Used for MRSA, severe C. diff. Oto and nephrotoxic. Red man syndrome if infused too quickly. Used along with gentamicin for MRSA endocarditis.

Question 22

S. viridens endocarditis?

Answer 22

Gentamicin and benzylpenicillin.