Vancomycin (AUC-guided), Aminoglycosides, Colistin/Polymyxin B
Action: Creatinine + urine output every 24–48h. Hold/reduce if SCr ↑ >0.5 from baseline
Imipenem (seizures), Cefepime (NCSE), Pip-Tazo (encephalopathy), Colistin (paresthesia), Metronidazole (cerebellitis long-term)
Action: Neuro checks, EEG if altered mental status
Oxacillin (cholestatic), Flucloxacillin (DILI), Metronidazole (prolonged use)
Action: LFTs every 1–2 weeks in prolonged therapy
Fluoroquinolones — QTc prolongation (especially moxifloxacin)
Azithromycin — QT prolongation
Action: Baseline ECG + QTc check. Hold if QTc >500ms
Linezolid + SSRIs = Serotonin syndrome
Nafcillin + Warfarin = ↓ INR
Vancomycin + Pip-Tazo = ↑ nephrotoxicity
Aminoglycosides + Loop diuretics = ↑ ototoxicity
Vancomycin — minimum 60 min/gram (Red Man prevention)
Colistin — infuse over 30–60 min
Caz-Avi — 2 hours
Meropenem EI — 3 hours
Pip-Tazo EI — 4 hours
| Drug | Normal CrCl | CrCl 30–50 | CrCl <30 / HD |
|---|---|---|---|
| Vancomycin | q8–12h (AUC-guided) | Extend interval, AUC guided | q24–96h or post-HD dosing |
| Daptomycin | q24h | q24h | q48h (post-HD) |
| Linezolid | q12h | No change | No change (use freely in AKI) |
| Colistin (CMS) | 9 MU load → 4.5 MU q12h | Reduce maintenance | Loading only, then guided by levels |
| Caz-Avi | 2.5g q8h | 1.25g q8h | 0.94g q24h (critical adjustment) |
| Meropenem | 1–2g q8h | 1g q12h | 500mg q24h (HD: post-dialysis) |
| Pip-Tazo | 4.5g q8h | 4.5g q8h | 2.25g q8h (max 2.25g q6h in HD) |
| Cefepime | 2g q8h | 2g q12h | 1g q24h (high neurotoxicity risk) |
| Carbapenem | Use When | Avoid When | Key Differentiator |
|---|---|---|---|
| Meropenem | ESBL, Pseudomonas, Meningitis, ICU empiric | No specific restriction beyond resistance | Lowest seizure risk, CNS safe |
| Imipenem | Broad empiric, no CNS infection | Epilepsy, CNS infection, renal failure | Highest seizure potential |
| Ertapenem | ESBL, OPAT, community-onset severe infection | Pseudomonas, Acinetobacter, ICU | Once daily, NO Pseudomonas |
| Doripenem | HAP/VAP, Pseudomonas, UTI | Limited approved indications | Extended infusion preferred |
Vancomycin → Daptomycin → Linezolid → Ceftaroline
Climb the ladder when the lower rung fails or is contraindicated. Daptomycin NEVER in lungs.
Daptomycin is inactivated by pulmonary surfactant.
Never use for pneumonia. Use Linezolid instead for MRSA pneumonia — better lung penetration.
Vancomycin → infuse Slowly or get
Low blood pressure + flushing
Oh no — Red Man Syndrome
Watch your rate!
Not true allergy. Rate-related histamine release.
Limit to 28 days
Inhibits MAO → Serotonin syndrome
No platelet count falling? Check weekly
Excellent oral bioavailability (IV→PO early)
Always switch to oral once patient improving.
Ertapenem covers Everything...
Except Pseudomonas, Acinetobacter, Enterococcus
The "PAE gap" — if any of these 3 are possible, escalate to Meropenem/Pip-Tazo
ImiPENEM = most epileptogenic carbapenem
Avoid in: epilepsy, meningitis, head injury
Use Meropenem for CNS infections instead
Cilastatin prevents nephrotoxic metabolite accumulation.
Colistin ALWAYS in combination
Mono = Resistance emerges
Combo = Meropenem + Colistin (synergistic for XDR)
Polymyxin B = more predictable PK than Colistin
For MSSA, always use:
Oxacillin or Nafcillin OVER Vancomycin
Outcomes proven superior with anti-staph penicillin.
Vancomycin for MSSA = inferior choice.
KPC Klebsiella? → Ceftazidime-Avibactam
NDM (Metallo-β-lactamase)? → CAZ-AVI + Aztreonam
Avibactam inhibits serine (A,C,D) NOT metallo enzymes. Aztreonam fills the NDM gap.
Tigecycline has very low serum levels
Never use for:
• Bacteremia
• UTI (low urine levels too)
• Endocarditis
Only for: Abdominal/skin infections when NOTHING else works.
Aminoglycosides need TWO levels:
Peak = efficacy (Cmax/MIC >8–10)
Trough = toxicity prevention (<1 for gent)
Extended interval dosing: ONE daily dose, check level at 6–14h to guide next dose.
Extended Infusion maximizes %Time > MIC
β-lactams are time-dependent killers.
Slow infusion → drug above MIC for longer → better killing
Pip-Tazo 4h, Meropenem 3h, Cefepime 3h = standard EI protocols.
β-lactams (Penicillins, Cephalosporins, Carbapenems, Aztreonam)
Kill best when drug stays above MIC for >40–70% of dosing interval
Strategy: Extended/continuous infusion
Aminoglycosides, Fluoroquinolones
Kill best at high peaks relative to MIC
Strategy: High single daily dose (HDI/EID) to maximize peak
Vancomycin, Fluoroquinolones, Tigecycline
Kill correlates with total drug exposure over time
Strategy: Vancomycin AUC/MIC 400–600 (ASHP 2020 guideline)
Endocarditis/device infection:
β-lactam + aminoglycoside = synergistic
Daptomycin + ceftaroline = salvage MRSA endocarditis
Biofilm: rifampicin added for device-associated infections
De-escalate when cultures return!
Broad → narrow based on susceptibility.
Carbapenems ≠ always needed.
Check: Is ESBL confirmed? Then carbapenem justified.
Aminoglycosides + Fluoroquinolones have prolonged PAE against GN organisms — bacteria don't regrow even after drug falls below MIC.
β-lactams have minimal PAE — must maintain levels continuously.
| GP | Gram Positive — retain crystal violet stain (purple) |
| GAS | Group A Streptococcus — S. pyogenes |
| GBS | Group B Streptococcus — S. agalactiae |
| VGS | Viridans Group Streptococci |
| MRSA | Methicillin-Resistant Staphylococcus aureus |
| MSSA | Methicillin-Sensitive Staphylococcus aureus |
| VRE | Vancomycin-Resistant Enterococcus (usually E. faecium) |
| VSE | Vancomycin-Sensitive Enterococcus |
| CoNS | Coagulase-Negative Staphylococci (e.g. S. epidermidis) |
| PBP2a | Penicillin-Binding Protein 2a — altered target in MRSA, mecA gene product |
| mecA | Gene encoding PBP2a — defines methicillin resistance |
| vanA/B | Vancomycin resistance genes in VRE — alter D-Ala-D-Ala → D-Ala-D-Lac |
| TSS | Toxic Shock Syndrome — toxin-mediated (TSST-1 in S. aureus) |
| PVL | Panton-Valentine Leukocidin — virulence toxin in community-MRSA |
| SBE | Subacute Bacterial Endocarditis |
| NF | Necrotizing Fasciitis — life-threatening deep tissue infection |
| SSTI | Skin and Soft Tissue Infection |
| PCN-S | Penicillin-Sensitive (susceptible) |
| PCN-R | Penicillin-Resistant |
| GN | Gram Negative — outer membrane + thin peptidoglycan; pink on Gram stain |
| GNR | Gram Negative Rods (Bacilli) |
| ESBL | Extended-Spectrum Beta-Lactamase — hydrolyses 3rd gen cephalosporins |
| KPC | Klebsiella pneumoniae Carbapenemase — class A serine carbapenemase |
| NDM | New Delhi Metallo-β-lactamase — MBL; hydrolyses all β-lactams incl. carbapenems |
| MBL | Metallo-Beta-Lactamase — includes NDM, VIM, IMP; zinc-dependent; NOT inhibited by avibactam |
| OXA | OXA-type carbapenemase — class D; common in Acinetobacter |
| AmpC | Chromosomal cephalosporinase — inducible; class C β-lactamase (e.g. Enterobacter) |
| MDR | Multi-Drug Resistant — resistant to ≥3 antibiotic classes |
| XDR | Extensively Drug-Resistant — resistant to all but 1–2 classes |
| PDR | Pan-Drug Resistant — resistant to ALL available antibiotics |
| ESKAPE | Enterococcus, S. aureus, Klebsiella, Acinetobacter, Pseudomonas, Enterobacter — major drug-resistant pathogens |
| CRAB | Carbapenem-Resistant Acinetobacter baumannii |
| CRKP | Carbapenem-Resistant Klebsiella pneumoniae |
| CRPA | Carbapenem-Resistant Pseudomonas aeruginosa |
| LPS | Lipopolysaccharide — endotoxin on GN outer membrane; triggers sepsis |
| HAP | Hospital-Acquired Pneumonia (≥48h after admission) |
| VAP | Ventilator-Associated Pneumonia — HAP in intubated patients |
| CAP | Community-Acquired Pneumonia |
| CABP | Community-Acquired Bacterial Pneumonia |
| HUS | Hemolytic Uremic Syndrome — Shiga toxin (EHEC O157:H7, S. dysenteriae) |
| DGI | Disseminated Gonococcal Infection |
| PID | Pelvic Inflammatory Disease |
| IJV | Internal Jugular Vein (Lemierre's syndrome) |
| AECOPD | Acute Exacerbation of Chronic Obstructive Pulmonary Disease |
| IV | Intravenous — administered directly into a vein |
| IM | Intramuscular injection |
| PO | Per Os — oral route (by mouth) |
| PCN | Penicillin (class of β-lactam antibiotics) |
| β-lactam | Antibiotic class with β-lactam ring: Penicillins, Cephalosporins, Carbapenems, Monobactams |
| Pip-Tazo | Piperacillin-Tazobactam (Zosyn) — ureidopenicillin + β-lactamase inhibitor |
| Caz-Avi | Ceftazidime-Avibactam (Avycaz) — 5th gen ceph + novel β-lactamase inhibitor |
| Vanco | Vancomycin — glycopeptide antibiotic |
| Dapto | Daptomycin — cyclic lipopeptide |
| Linezo | Linezolid — oxazolidinone |
| Mero | Meropenem — carbapenem antibiotic |
| Imipenem | Imipenem-Cilastatin — carbapenem + renal dehydropeptidase inhibitor |
| Erta | Ertapenem — once-daily carbapenem (no Pseudomonas cover) |
| TMP-SMX | Trimethoprim-Sulfamethoxazole (Co-trimoxazole, Bactrim) |
| FQ | Fluoroquinolone (Ciprofloxacin, Levofloxacin, Moxifloxacin) |
| Metro | Metronidazole — nitroimidazole antianaerobic/antiprotozoal |
| Azithro | Azithromycin — macrolide antibiotic (atypical cover) |
| Gent | Gentamicin — aminoglycoside |
| Amik | Amikacin — aminoglycoside (more resistant to modifying enzymes) |
| Colistin | Colistimethate Sodium (CMS) — polymyxin E; last-resort for XDR GNR |
| Polymyxin B | Polymyxin class antibiotic; NOT renally cleared (preferred over colistin in AKI) |
| Tige | Tigecycline — glycylcycline (tetracycline derivative); low serum levels |
| Rifamp | Rifampicin — RNA polymerase inhibitor; added for biofilm/device infections |
| Ceftri | Ceftriaxone — 3rd gen cephalosporin |
| Cefepime | 4th generation cephalosporin — anti-pseudomonal |
| Ceftaroline | 5th generation cephalosporin — only β-lactam with MRSA activity |
| Aztreonam | Monobactam — GN only; safe in PCN allergy; pairs with Caz-Avi for NDM |
| Fidaxo | Fidaxomicin — macrocyclic antibiotic for C. diff recurrence prevention |
| TIG | Tetanus Immune Globulin — human antitoxin for tetanus |
| ORS | Oral Rehydration Solution — mainstay of cholera management |
| PK | Pharmacokinetics — what the body does to the drug (ADME) |
| PD | Pharmacodynamics — what the drug does to the body/bug |
| AUC | Area Under the Curve — total drug exposure over time (mg·h/L) |
| MIC | Minimum Inhibitory Concentration — lowest drug concentration inhibiting visible bacterial growth |
| AUC/MIC | PK/PD target for vancomycin (goal 400–600) and fluoroquinolones |
| T>MIC | Time above MIC — PK/PD target for β-lactams (time-dependent killing) |
| Cmax | Peak serum concentration — relevant for aminoglycosides (concentration-dependent killers) |
| Cmin | Trough (minimum) concentration — monitored to avoid toxicity |
| EI | Extended Infusion — prolonged infusion of β-lactams to maximize T>MIC |
| EID | Extended Interval Dosing — aminoglycosides given once daily in high dose |
| HDI | High Dose Interval dosing — same as EID for aminoglycosides |
| PAE | Post-Antibiotic Effect — bacteria don't regrow even after drug falls below MIC |
| CrCl | Creatinine Clearance — used to estimate renal function and guide dosing (mL/min) |
| SCr | Serum Creatinine — renal function marker (μmol/L or mg/dL) |
| AKI | Acute Kidney Injury — requires drug dose adjustment |
| HD | Hemodialysis — affects drug clearance; most drugs need post-HD supplemental dosing |
| CRRT | Continuous Renal Replacement Therapy — used in ICU; specific dosing guidance needed |
| CPK | Creatine Phosphokinase — muscle enzyme; monitored with daptomycin (myopathy) |
| LFT | Liver Function Tests — monitored with hepatotoxic agents (oxacillin) |
| CBC | Complete Blood Count — monitored with linezolid (myelosuppression) |
| QTc | Corrected QT Interval — cardiac arrhythmia risk; fluoroquinolones, azithromycin |
| TDM | Therapeutic Drug Monitoring — measuring serum drug levels (vancomycin, aminoglycosides) |
| IBW | Ideal Body Weight — used for aminoglycoside and colistin dosing (not actual weight) |
| ABW | Adjusted Body Weight — used for vancomycin dosing in obesity |
| NMJ | Neuromuscular Junction — site of aminoglycoside-induced blockade; ↑ risk in myasthenia gravis |
| MAO | Monoamine Oxidase — inhibited by linezolid → serotonin syndrome risk with SSRIs/SNRIs |
| SSRI | Selective Serotonin Reuptake Inhibitor — avoid with linezolid (serotonin syndrome) |
| SNRI | Serotonin-Norepinephrine Reuptake Inhibitor — avoid with linezolid |
| CYP3A4 | Cytochrome P450 enzyme — nafcillin induces it, reducing warfarin effect |
| INR | International Normalized Ratio — anticoagulation measure; affected by nafcillin |
| OPAT | Outpatient Parenteral Antibiotic Therapy — home IV antibiotics (e.g. ertapenem once daily) |
| CMS | Colistimethate Sodium — prodrug form of colistin; requires renal activation (unlike Polymyxin B) |
| ASHP | American Society of Health-System Pharmacists — published 2020 vancomycin AUC guidelines |
| ICU | Intensive Care Unit |
| BSI | Bloodstream Infection — bacteremia; positive blood cultures |
| IE | Infective Endocarditis — infection of heart valves; requires 4–6 weeks IV antibiotics |
| NVE | Native Valve Endocarditis |
| PVE | Prosthetic Valve Endocarditis |
| CIED | Cardiac Implantable Electronic Device (pacemaker/ICD) — biofilm infection |
| CRBSI | Catheter-Related Bloodstream Infection |
| CLABSI | Central Line-Associated Bloodstream Infection |
| UTI | Urinary Tract Infection |
| cUTI | Complicated UTI — structural/functional abnormality or catheter-associated |
| IAI | Intra-Abdominal Infection |
| SBP | Spontaneous Bacterial Peritonitis — in cirrhosis; E. coli / Klebsiella / Streptococcus |
| CNS | Central Nervous System (brain + spinal cord) |
| BBB | Blood-Brain Barrier — few antibiotics penetrate well (linezolid, metronidazole, TMP-SMX) |
| CSF | Cerebrospinal Fluid — sampled by LP; bacteremia CSF glucose/protein/culture |
| LP | Lumbar Puncture (Spinal Tap) — to obtain CSF for meningitis diagnosis |
| NCSE | Non-Convulsive Status Epilepticus — cefepime/imipenem neurotoxicity; subtle altered mental status |
| EEG | Electroencephalogram — used to diagnose NCSE in altered mental status |
| CF | Cystic Fibrosis — chronic Pseudomonas aeruginosa lung colonization |
| DILI | Drug-Induced Liver Injury — e.g. flucloxacillin cholestatic hepatitis |
| IUD | Intrauterine Device — associated with Actinomyces israelii pelvic infection |
| MALT | Mucosa-Associated Lymphoid Tissue — H. pylori-associated MALT lymphoma |
| UBT | Urea Breath Test — non-invasive H. pylori detection (urease splits C13-labelled urea) |
| GDH | Glutamate Dehydrogenase — antigen test for C. diff screening (high sensitivity) |
| PMN | Polymorphonuclear Neutrophil — white blood cells; seen with intracellular gonococci on Gram stain |
| CLO | Campylobacter-Like Organism test — rapid urease test for H. pylori on gastric biopsy |
| BCYE | Buffered Charcoal Yeast Extract agar — required for Legionella culture |
| GDH | Glutamate Dehydrogenase — C. difficile antigen test; high sensitivity screening |
| PICC | Peripherally Inserted Central Catheter — common route for OPAT delivery |
| ICP | Intracranial Pressure — elevated in bacterial meningitis; give dexamethasone |
| hvKp | Hypervirulent Klebsiella pneumoniae — liver abscess, string test positive |
| q4h | Every 4 hours (6 times daily) — e.g. Oxacillin/Nafcillin |
| q6h | Every 6 hours (4 times daily) |
| q8h | Every 8 hours (3 times daily) — most common β-lactam interval |
| q12h | Every 12 hours (twice daily — BD) |
| q24h | Every 24 hours (once daily — OD) |
| q48h | Every 48 hours — used in renal failure dosing |
| mg/kg | Milligrams per kilogram body weight — weight-based dosing |
| MU | Million Units — used for polymyxin B/colistin dosing (e.g. 9 MU loading dose) |
| BD | Bis Die — twice daily (same as q12h) |
| TDS / TID | Three times daily (same as q8h) |
| OD / QD | Once daily (same as q24h) |
| PRN | Pro Re Nata — as needed |
| STAT | Immediately — first dose urgency |
| Load | Loading dose — initial high dose to rapidly achieve therapeutic levels |
| Maint. | Maintenance dose — regular dose to sustain therapeutic levels |
| HD dose | High-Dose strategy — e.g. daptomycin 10–12 mg/kg for VRE endocarditis |
| Max | Maximum dose — not to be exceeded regardless of weight |
| PO/IV | Switch from IV to oral — possible with linezolid (100% bioavailability) |
This reference guide — every drug, every dose, every mnemonic — was crafted with hundreds of hours of clinical knowledge by Dr. Muhammad Zain Abbas to help medical students and doctors learn faster and save lives.
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