Antibiotics Flashcards
Amoxicillin: renal and hepatic dose adjustments
Primarily eliminated by kidneys
Renally reduce dose if eGFR < 30
No hepatic dose adjustment
Antibiotics most associated with pseudomembranous colitis
Amoxicillin/penicillins, clindamycin, cephalosporins and fluoroquinolones
Cell wall active antibiotics (bacteriocidal)
BETA LACTAMS
- Penicillins
- Cephalosporins
- Monolactams
- Carbapenems
GLYCOPEPTIDES
- Only slowly bactericidal, act more bacteriostatic
- LESS effective than beta lactams against sensitive organisms
Antibiotics that cause inhibition of protein synthesis (bacteriostatic)
- Aminoglycosides (EXCEPTION to the rule - actually bacteriocidal)
- Macrolides
- Tetracyclines
- Lincosamides
- Oxazolidinones
Antibiotics with other MOA (not cell wall, not inhibition of protein synthesis)
- Nitroimidazoles (DNA strand breakage)
- Quinolones (DNA gyrase inhibitors)
- Trimethoprim and sulphas (anti folate agents - relative selectivity for bacterial enzymes)
Penicillins
- MOA
- Bacteriostatic or cidal
- Excretion
- Key A/E
- Cell wall active
- Bactericidal
- Renally excreted
- Generally safe - allergy is main A/E
Penicillin (drug):
- Routes
- Spectrum
- Excretion
- A/E
- Oral, IM, IV
Spectrum:
- Drug of choice: strep and listeria
- Enterococci and anaerobes (not bacteroides)
- Most staph and gram negs now resistant
Renally excreted
Safe unless allergic
“enteric active” penicillins:
- Drugs
- Spectrum
- Excretion
- A/E
Drugs:
- Amoxicillin (PO, IV), ampicillin (IV)
Spectrum:
- Enterococci (DOC)
- Strep (avoid with EBV - rash)
- Anaerobes (not bacteroides)
- Most gram negatives now resistant
- not great for staph
Renally excreted
Safe unless allergic
“Antistaph” penicillins
- Drugs
- Spectrum
- Toxicity
Drugs:
- Flucloxacillin (PO/IV) & dicloxacillin (PO)
Spectrum:
Exclusively gram positive
- Staph (MSSA) DOC
- Strep (less effective than penicillins)
- NOT enterococci, gram negatives, anaerobes
A/E:
- Allergy
- Hepatotoxicity! Esp in elderly
- Irritates veins
“Antipseudomonal” penicillins:
- Drugs
- Spectrum
- Toxicity
- When to use
Drugs:
- Ticarcillin/piperacillin
(not as individual drugs anymore)
Spectrum:
- Gram negatives including pseudomonas
- Strep
- Staph (not MRSA)
- Enterococci
- Anaerobes (not bacteroides)
Toxicity:
- Allergy
BROAD SPECTRUM - ONLY USE WHEN SERIOUS GRAM NEG SEPSIS IS SUSPECTED
Pencillins with B-lactamase inhibitors
- Drugs
- Spectrum
- Toxicity
Drugs:
- Augmentin (PO): amoxi + clavulanic acid
- Tazocin (IV): piperacillin + tazobactam
- Timentin (IV): ticarcillin + clavulanic acid
Spectrum:
- Staph (not MRSA)
- Strep
- Enterococci
- Gram negatives
- Pseudomonas (only timentin/tazocin)
- Anaerobes
Toxicity:
- Allergy (augmentin) - rash in EBV
- Clavulanic acid/tazobactam can cause hepatotoxicity
- Augmentin: GI upset
BROAD SPECTRUM AGENTS - not first line, but useful when wide range of potential pathogens exists
ALL enterococci are intrinsically resistant to ALL….
Cephalosporins!
Cephalosporin generations and their spectrums
1st generation (cephalexin, cephazolin): - Staph (not MRSA), strep and limited gram negatives
2nd generation (cefuroxime): - As above + haemophilus
3rd generation (ceftriaxone):
- Gram negatives and strep
- Does NOT cover pseudomonas
- Limited staph cover
4th generation (cefepime, ceftazidime):
- Gram negatives (including pseudomonas)
- Some staph cover, strep (cefepime)
5th generation (ceftaroline):
- Gram negs + MRSA activity
- limited pseudo
Cephalosporins - increasing gen, less staph cover, more gram neg cover
4th gen covers pseudomonas
Cephalosporins:
- Indications
- A/E
Indications:
- Consider in penicillin allergic patients
- Gram negative cover in renal impairment or pregnancy
- Meningitis
A/E:
- Hypersensitivity
- Broad spectrum - overuse strongly associated with development of VRE
Monobactams
- Drugs
- Spectrum
- Toxicity
- Indications
Drugs: aztreonam (IV)
Spectrum: gram negatives including pseudomonas
(NO gram pos, anaerobes)
A/E: hypersensitivity
Indications: limited. Serious gram negative infections resistant to other agents
Carbapenems:
- Drugs
- Spectrum
- Toxicity
- Excretion
Drugs: meropenem (IV)
Spectrum: INSANELY broad – most bacteria except MRSA and ampicillin resistant enterococci
Toxicity: allergy - but often safe in pencillin allergic pt, seizures
Renally excreted
Glycopeptides
- Drugs
- Spetrum
- Problems
Drugs: vancomycin (IV) or teicoplanin (IV or IM)
Spectrum:
- Gram positive aerobes only
- First line for MRSA and ampicillin R enterococci
Problems:
- VRE
- 100% renally excreted - needs levels monitored
- Synergistic nephrotoxicity with aminoglycosides
- Red man syndrome
Beta lactam antibiotic table - see studying w pictures ppt slide 2
…
Aminoglycosides
- Drugs
- Spectrum
- Excretion
- Toxicity
Drugs: gentamicin (IV or IM), tobramycin, amikacin
Spectrum:
- Gram negs including pseudomonas
- Used for synergy in staph and enterococcal endocarditis
Renally excreted (dose adjust)
Toxicity:
- MUST monitor levels
- Nephrotoxic, ototoxic (hair cells)
- Vestibular dysfunction
Most indications do not need more than 48 hours aminoglycoside therapy
Can be effective and cheap if used well
Macrolides
- Drugs
- Spectrum
- Toxicities
- Uses
Drugs: Erythromycin (oral or IV), roxithromycin, clarithromycin, azithromycin
Spectrum:
- Varies
- Staph and streph
- Atypical organisms including legionella
Toxicities:
- Sclerosing to IVC
- GIT upset with all forms
- Hepatotoxicity
- Drug interactinos
Uses:
- PO rx less serious pneumonia
- Minor gram +ve infections in beta lactam allergic pt
- Atypical organisms: chlamydia, legionella
Tetracyclines
- Drugs
- Spectrum
- Toxicity
Doxycycline (PO)
Spectrum:
- Complex
- Mainly used against atypicals: malaria prophylaxis, chlamydia spcc, rickettsia
Toxicity:
- Photosensitivity
- Erosive oesophagitis
- Deposits in teeth/bones of children/fetus - CI in children and pregnancy
Lincosamides
- Drugs
- Spectrum
- Bioavailability
- TZoxicity
- Clindamycin (PO, IV), licomycin (IV)
- Spectrum: staph (some strains of MRSA), strep, anaerobes
- Excellent PO bioavailability
- Toxicity: GIT upset (PO), c diff
Oxazolidinones
- Drugs
- MOA
- Bioavailability
- Spectrum
- Toxicities
- Uses
- Linezolid (PO or IV)
- Inhibits initiation of protein synthesis
- 100% PO bioavailability
Spectrum: gram positives inc MRSA
Toxicities:
- Dose related myelosuppression (esp thrombocytopenia)
- Peripheral neuropathy
- Minor AEs - bad taste, rash, GIT upset
Uses:
- Never first line
- Treatment of resistant gram positive organisms
or unable to tolerate better options
Nitroimidazoles
- Drugs
- Spectrum
- Bioavailability
- Toxicity
- Metronidazole (PO or IV)
- Spectrum: anaerobes (first line drug)
- Excellent PO bioavailability
Toxicity Metallic taste GIT upset Interaction with alcohol Peripheral neuropathy
DOC for c diff colitis
Quinolones
Drugs: ciprofloxacin (PO or IV)
Spectrum:
- Gram negatives including pseudomonas
- Sometimes used in combinations against staph
- Atypical organisms
Excellent bioavailability
Toxicity:
- tenosynovitis
- possible cartilage problems in children/foetus
Newer quinolones e.g. moxiflox have better gram positive activity
Trimethoprim
- Spectrum
- Main use
- TOxicity
Spectrum: limited gram negative and positive aerobes
Main use - UTIs
Toxicity: rash/itch, may increase serum K+ (blocks distal tubular secretion of K+ and reabsorption of Na+) and may increase serum Cr (competes for tubular secretion of Cr)
Trimethoprim / sulphamethoxazole (PO, IV)
Spectrum: gram negative aerobes, gram positive aerobes, some atypicals (DOC for PJP)
Toxicity: GI upset Rash common (poss. Steven Johnson) Bone marrow suppression All trimethoprim A/E can also occur
Mainly used for chest sepsis, urinary sepsis, PJP prophylaxis or treatment
Mechanism of resistance in VRE?
VAN A and VAN B genes !!
Alteration of the peptidoglycan synthesis pathway -
D-Ala-D-Ala becomes D-Ala-D-Lac or D-Ala-D-Ser
UTI caused by VRE ?
Despite being a VRE, antibiotic of choice is still amoxicillin due to large amounts of amoxi concentration you can achieve in the urine
