Antibacterial Drugs Flashcards
Penicillin G
Action: Block transpeptidase cross-linking of peptidoglycan; prototype beta-lactam.
Uses: Gram-positive organisms (S. pneumoniae, S. pyogenes, Actinomyces); N. meningitidis; T. palliduim.
Toxicity: Hypersensitivity reactions; hemolytic anemia.
Resistance: Penicillinase-sensitive.
Ampicillin
Action: Block transpeptidase cross-linking of peptidoglycan; aminopenicillin.
Uses: Extended-spectrum penicillin = H. influenzae, E. coli, L. monocytogenes, P. mirabilis, Salmonella, Shigella, enterococci.
Toxicity: Hypersensitivity reactions; rash; pseudomembranous colitis.
Resistance: Penicillinase-sensitive.
Other drugs in class: Amoxicillin.
Nafcillin
Action: Block transpeptidase cross-linking of peptidoglycan; penicillinase-resistant penicillin.
Uses: S. aureus (except MRSA).
Toxicity: Hypersensitivity reactions; interstitial nephritis.
Resistance: MRSA resistance via altered PBPs.
Other drugs in class: Oxacillin; dicloxacillin.
Piperacillin
Action: Block transpeptidase cross-linking of peptidoglycan; antipseudomonal.
Uses: Pseudomonas spp. and gram-negative rods.
Toxicity: Hypersensitivity reactions.
Resistance: Penicillinase-sensitive.
Other drugs in class: Ticarcillin.
Clavulanic acid
Action: β-lactamase inhibitor.
Uses: Added to penicillin antibiotics to protect the antibiotic from destruction by β-lactamase (penicillinase).
Other drugs in class: Sulbactam; tazobactam.
Cefazolin
Action: Block transpeptidase cross-linking of peptidoglycan; 1st generation cephalosporin.
Uses: Gram- positive cocci; Proteus mirabilis; E. coli, Klebsiella pneumoniae; used prior to surgery to prevent S. aureus wound infections.
Toxicity: Hypersensitivity reactions; vitamin K deficiency; increase nephrotoxicity of aminoglycosides.
Resistance: penicillinase-sensitive (better than PCN).
Other drugs in class: cephalexin.
Cefoxitin
Action: Block transpeptidase cross-linking of peptidoglycan; 2nd generation cephalosporin.
Uses: Gram-positive cocci; H. influenzae, Enterobacter aerogenes, Neisseria spp., Proteus mirabilis, E. coli, Klebsiella pneumoniae, Serratia marcescens.
Toxicity: Hypersensitivity reactions; vitamin K deficiency; increase nephrotoxicity of aminoglycosides.
Resistance: penicillinase-sensitive (better than PCN).
Other drugs in class: cefaclor; cefuroxime.
Ceftriaxone
Action: Block transpeptidase cross-linking of peptidoglycan; 3rd generation cephalosporin.
Uses: Serious gram-negative infections resistant to other β-lactams.
Toxicity: Hypersensitivity reactions; vitamin K deficiency; increase nephrotoxicity of aminoglycosides.
Resistance: penicillinase-sensitive (better than PCN).
Other drugs in class: cefotaxime; ceftazidime.
Cefepime
Action: Block transpeptidase cross-linking of peptidoglycan; 4th generation cephalosporin.
Uses: High activity against Pseudomonas and gram-positive organisms.
Toxicity: Hypersensitivity reactions; vitamin K deficiency; increase nephrotoxicity of aminoglycosides.
Resistance: penicillinase-sensitive (better than PCN).
Ceftaroline
Action: Block transpeptidase cross-linking of peptidoglycan; 5th generation cephalosporin.
Uses: Broad gram-positive and gram-negative organism coverage, including MRSA; does not cover Pseudomonas.
Toxicity: Hypersensitivity reactions; vitamin K deficiency; increase nephrotoxicity of aminoglycosides.
Resistance: penicillinase-sensitive (better than PCN).
Aztreonam
Action: Block transpeptidase cross-linking of peptidoglycan; monobactam.
Uses: Gram-negative rods only.
Toxicity: Well tolerated; GI upset.
Meropenem
Action: Block transpeptidase cross-linking of peptidoglycan; carbapenem; penicillinase-resistant.
Uses: Wide spectrum; gram-positive cocci; gram-negative rods; anaerobes.
Toxicity: GI distress; skin rash; CNS toxicity (seizures) at high plasma levels.
Other: Always administered with cilastatin (inhibitor of renal dehydropeptidase I) to increase inactivation of drug in renal tubules.
Other drugs in class: Imipenem; ertapenem; doripenem.
Vancomycin
Action: Inhibits cell wall peptidoglycan formation by binding D-ala D-ala portion of cell wall precursors.
Uses: Gram positive only; serious, multidrug-resistant organisms, including MRSA, enterococci, and Clostridium difficile (oral dose for pseudomembranous colitis).
Toxicity: Well tolerated in general; nephrotoxicity, ototoxicity, thrombophlebitis; diffuse flushing (red man syndrome).
Resistance: Amino acid modification.
Daptomycin
Action: Rapid depolarization of the cell membrane.
Uses: Multi-resistant gram positives, notably VRE, MRSA, and corynebacteria.
Toxicity: Less serious and common (diarrhea, N/V, sore throat); more serious and uncommon (rhabdomyolysis, renal failure, asthmatic pulmonary eosinophilia).
Gentamicin
Action: Aminoglycoside protein synthesis inhibitor; binds 30S (inhibits initiation and translocation); mRNA misreading; bactericidal.
Uses: Severe gram-negative rod infections; synergistic with beta-lactams; neomycin for bowel surgery.
Toxicity: Nephrotoxicity; neuromuscular blockade; ototoxicity; teratogen.
Resistance: Inactivation by bacterial transferase enzymes.
Other: requires oxygen for uptake; no action against anaerobes.
Other drugs in class: Neomycin; amikacin; tobramycin; streptomycin.
Doxycycline
Action: Tetracycline protein synthesis inhibitor; binds 30S (prevent attachment of aminoacyl-tRNA); bacteriostatic.
Uses: B. burgdorferi; M. pneumoniae; Rickettsia; Chlamydia; used to treat acne.
Toxicity: GI distress; discoloration of teeth and inhibition of bone growth in children; photosensitivity; contraindicated in pregnancy.
Resistance: Plasmid-encoded transport pumps decrease uptake and increase efflux.
Other: Doxycycline eliminated fecally (use in renal failure); divalent cations inhibit gut absorption.
Other drugs in class: Tetracycline; minocycline.
Azithromycin
Action: Macrolid protein synthesis inhibitor; binds the 23S rRNA of 50S (blocks translocation); bacteriostatic.
Uses: Atypical pneumonias (Mycoplasma, Chlamydia, Legionella); STDs (for Chlamydia); gram- positive cocci (streptococcal infections in patients allergic to penicillin).
Toxicity: Gastrointestinal motility issues, arrhythmia caused by prolonged QT, acute cholestatic hepatitis, rash, eosinophilia.
Resistance: Methylation of 23S rRNA-binding site.
Other drugs in class: Clarithromycin; erythromycin.
Chloramphenicol
Action: Protein synthesis inhibitor; binds 50S (blocks peptidyltransferase); bacteriostatic.
Uses: Meningitis (H. influenzae, N. meningitidis, S. pneumoniae); rocky mountain spotted fever (Rickettsia rickettsii).
Toxicity: Anemia (dose dependent); aplastic anemia (dose independent); gray baby syndrome.
Resistance: Plasmid-encoded acetyltransferase inactivates drug.
Clindamycin
Action: Lincosamide protein synthesis inhibitor; binds 50S (blocks translocation); bacteriostatic.
Uses: Anaerobic infections (e.g., Bacteroides spp., C. perfringens) above the diaphragm; GAS infections.
Toxicity: Pseudomembranous colitis (C. difficile overgrowth); fever; diarrhea.
Sulfamethoxazole (SMX)
Action: Sulfonamide inhibitor of folate synthesis; competitive antagonist of dihydropteroate synthase (DHPS); bacteriostatic.
Uses: Gram-positive; gram-negative; Nocardia; Chlamydia; UTI.
Toxicity: Hypersensitivity reactions; hemolysis if G6PD deficient; nephrotoxicity (tubulointerstitial nephritis); photosensitivity; kernicterus in infants.
Resistance: altered DHPS; decreased uptake; increase PABA production.
Other drugs in class: Sulfisoxazole; sulfadiazine.
Trimethoprim
Action: Inhibitor of folate synthesis; inhibits dihydrofolate reductase (DHFR); bacteriostatic.
Uses: Combination with sulfonamides (trimethoprim-sulfamethoxazole [TMP- SMX]), causing sequential block of folate synthesis; combination used for UTIs, Shigella, Salmonella, Pneumocystis jirovecii pneumonia treatment and prophylaxis, and toxoplasmosis prophylaxis.
Toxicity: Megaloblastic anemia; leukopenia; granulocytopenia.
Ciprofloxacin
Action: Fluoroquinolone inhibitor of DNA gyrase (topoisomerase II) and topoisomerase IV; bactericidal.
Uses: Gram-negative rods of urinary and GI tracts (including Pseudomonas); Neisseria; some gram-positive organisms.
Toxicity: GI upset; superinfections; skin rashes; headache; dizziness; tendonitis; tendon rupture; leg cramps; myalgias.
Resistance: Mutation in DNA gyrase; plasmid-mediated resistance; efflux pumps.
Other drugs in class: Norfloxacin; levofloxacin; ofloxacin, sparfloxacin; moxifloxacin; gemifloxacin; enoxacin; nalidixic acid (quinolone).
Metronidazole
Action: Damage bacterial DNA via free radical production; bactericidal; antiprotozoal.
Uses: Giardia, Entamoeba, Trichomonas, Gardnerella vaginalis, anaerobes (Bacteroides, C. difficile); used with a proton pump inhibitor and clarithromycin for “triple therapy” against H. Pylori.
Toxicity: Disulfiram-like reaction (severe flushing, tachycardia, hypotension) with alcohol; headache; metallic taste.
Quinupristin/Dalfopristin
Action: Streptogramin protein synthesis inhibitor; binds 50S; bacteriostatic.
Uses: E. faecium; MSSA and MRSA.
Toxicity: Venous inflammation; arthralgia.
Rifampin
Action: Inhibits DNA-dependent RNA polymerase; rifamycins.
Uses: Mycobacterium tuberculosis; delays resistance to dapsone when used for leprosy; meningococcal prophylaxis and chemoprophylaxis for H. influenzae type B.
Toxicity: Minor hepatotoxicity and drug interactions (induces P-450); orange body fluids (nonhazardous side effect).
Other drugs in class: Rifabutin.
Isoniazid
Action: Decreased synthesis of mycolic acid.
Uses: Mycobacterium tuberculosis; only agent used as solo prophylaxis against TB.
Toxicity: Neurotoxicity; hepatotoxicity; pyridoxine (vitamin B6) can prevent neurotoxicity and lupus.
Other: prodrug must be activated by bacterial catalase-peroxidase.
Pyrazinamide
Action: Uncertain; thought to acidify intracellular environment.
Uses: Mycobacterium tuberculosis.
Toxicity: Hyperuricemia; hepatotoxicity; polyarthralgia.
Ethambutol
Action: Decrease carbohydrate polymerization of mycobacterium cell wall by blocking arabinosyltransferase.
Uses: Mycobacterium tuberculosis.
Toxicity: Optic neuropathy (red-green color blindness).
Linezolid
Action: Protein synthesis inhibitor; binds 50S; bacteriostatic.
Uses: Serious gram positives like VRE and MRSA.
Toxicity: Thrombocytopenia.
