💊370: Antibiotics Flashcards
What are the shape classifications of bacteria?
- Bacillus/bacilli - Rod shaped
- Coccus/cocci - Spherical
- Spirilla - Spiral
Bactericidal
Kill organism by cell lysis
For infection at sites of poor penetration
Bacteriostatic
Inhibit bacterial replication
Rely on host immune system (thus not immunocompromised)
Speciation
Identify bacterial species
Biochemical tests, PCR, etc
Culture and Sensitivity (C&S) Testing
Sensitive (S)
Intermediate (I)
Resistant (R)
To each antibiotic tested
Which sites do antibiotics generally have poor penetration to?
- Brain
- Bone
- Heart
- Abscesses - require surgical drainage
Need ⬆️ doses to sites of poor penetration
Which antibiotics should be avoided in pregnancy as they cross the placenta?
- Fluoroquinones
- Metronidazole
- Septra (Trimethoprim)
- Tetracyclines
(For Mother’s Safe-T Treatment)
What are the different effects of combination therapy?
- Additive response
- Synergistic response
- Antagonistic response
When is antibiotic combination therapy used?
- Severe infection
- Multiple infections
- Resistance prevention
- Decreasing toxicity (dec doses)
- Synergistic activity
What are factors to consider during antibiotic dosing?
- Weight
- Site of infection
- Route of elimination
- Time- vs concentration-dependent killing
What is the Minimum Inhibitory Concentration (MIC)?
Lowest concentration of antibiotic required to inhibit visible bacterial growth in vitro
Lower MIC = more effective antibiotic against that organism
Time-dependent killing Antibiotics
Determined length of time drug remains above MIC
Ex. Penicillins, cephalosporins, erythromycin
Concentration-dependent killing Antibiotics
Rate and extent of killing improved with high peak drug concentration
Ex. Aminoglycosides, fluoroquinolones
Renal Dose Adjustment
Required for agents with high renal elimination
Time-dependent killing = ⬇️ dose
Concentration-dependent killing = ⬆️ interval
What factors help determine when to stop antibiotic treatment?
- Host defenses
- Site of infection
- Infecting pathogen
- Negative cultures
- Patient response
Patient assessment and monitoring on antibiotic treatments?
- Leukocytes (⬆️WBC, ⬆️neutrophils)
- Metabolism (⬇️ nitrogen, Mg2+, K+, PO4-)
- CV effects (⬆️HR, ⬆️RR, ⬇️BP)
- Renal effects (Proteinuria, dehydration, ⬇️ renal perfusion, ⬇️urine output)
- Site-specific symptoms (UTI, pneumonia, meningitis)
When should a nurse be concerned while evaluating antibiotic efficacy?
- Fever unresolved after 3 days
- Signs and symptoms increased/unresolved
- Continued symptoms after course of therapy complete
What are common indications for antibiotic prophylaxis?
- Surgical procedures
- Bacterial endocarditis
- Neutropenia
- Other (recurrent UTI, HIV+, transplant, immunosuppression)
What are examples of resistant strains (“superbugs”)?
- Enterococcus (VRE)
- Staphylococcus aureus (MRSA)
- Escherichia coli
- Pseudomonas aeruginosa
What is the leading cause of antibiotic resistance?
Misuse and overuse of antibiotics
How do bacteria become resistant?
Adaptive changes:
- Drug metabolizing enzymes
- Decreased uptake of drugs
- Microbial drug receptors
- Synthesis of compounds that antagonize drug action
What is the mechanism of action of Beta-Lactam Antibiotics?
Inhibit bacterial cell wall synthesis
(Bactericidal)
Target penicillin-binding protein (PBP) on cell cytoplasmic membrane (basis of selectivity)
What are drug classes of Beta-Lactam antibiotics?
- Penicillins
- Cephalosporins
- Carbapenems
What are types of penicillins?
- Natural penicillins (narrow spectrum)
- Penicillinase-resistant penicillins
- Aminopenicillins
- Extended-spectrum penicillins
- Penicillins + beta-lactamase inhibitor
Why does penicillin resistance arise?
Penicillinase
Gram negative cell envelope
What are natural penicillins?
Penicillin G = IV form
Penicillin V = oral form
Narrow spectrum
Sensitive gram positive cocci
What is the mechanism of action of bacteria resistance to penicillin?
Bacteria produce enzyme beta-lactamase (penicillinase) that cleaves the Beta-lactam ring to inactivate penicillin
What is a prototype of penicillinase-resistant penicillins?
Cloxacillin
Only agent effective against staphylococcus
Not effective against MRSA
What are the main agents of aminopenicillins?
Ampicillin (IV/PO)
Amoxicillin (PO)
Broader spectrum
Penetrate gram negative cell envelope
What are common therapeutic uses for aminopenicillins?
UTI
Respiratory tract infection
Otitis media
What is the main agent of antipseudomonal penicillins?
Piperacillin (IV)
Broad spectrum (penetrated gram negative cell envelope)
Active against pseudomonas
What are common therapeutic uses for antipseudomonal penicillins?
Serious infections (ie sepsis) due to Pseudomonas
What is the use for penicillins + Beta-Lactamase inhibitors?
Broadens spectrum of activity
Amoxicillin + clauvinic Acid (Clavulin) (PO)
Piperacillin + tazobactam (Tazocin)(IV)
Cephalosporins
- More resistant to beta-lactamases
- ⬆️ gram negative, ⬇️ gram positive
- ⬆️ CSF penetration
4 generations in Canada
What are examples and common therapeutic uses of First generation cephalosporins?
Cefazolin IV, cephalexin PO
- Skin and soft tissue infections
- Surgical site infection prophylaxis
What are examples and common therapeutic uses of Second generation cephalosporins?
Cefaclor PO, cefuroxime PO/IV
Respiratory tract infections
What are examples and common therapeutic uses of Third and Fourth generation cephalosporins?
3rd: ceftriaxone, ceftazidime
4th: cefepime IV
Severe infections (meningitis, febrile neutropenia)
**3rd gen can lead to C-diff
What are examples and therapeutic uses of Carbapenems?
Ex. Imipenem, meropenem
Broadest spectrum agents
Resistant to penicillinases
Parenteral forms ONLY
What are side effects of Beta-Lactams?
GI: n/v, diarrhea
Neuro: seizures (penicillins; impenem at high IV doses)
Dermatologic: thrombophlebitis (minimize by diluting dilution and slowing infusión time)
Allergic reactions
Antibiotic allergy
Symptoms: itching, rash, face swelling, urticaria, flushing, dizziness, syncope, wheezing, throat tightness, trouble breathing
Management: antihistamines, corticosteroids, epinephrine
What are the pharmakinetics and drug interactions of Beta-Lactams?
Short half-lives
Better absorption on empty stomach (ex. Cloxacillin)
What is the mechanism of action of Vancomycin?
Inhibits cell wall synthesis (bactericidal)
Large molecule, not orally absorbed
What are common therapeutic uses for Vancomycin?
- MRSA
- Serious infections in penicillin-allergic pts
- C. difficile (only orally)
Which antibiotic induces Red Man Syndrome?
Vancomycin
What is Red Man Syndrome?
Histamine-mediated reaction
- flushing of trunk, neck and face
- hypotension
Management: slow infusion rate, antihistamines
What are side effects of Vancomycin?
- Red Man Syndrome
2. Nephrotoxicity (avoid high trough levels)
What are dosing and administration requirements of Vancomycin?
IV and PO forms
Renal dose adjustment required (IV only)
What is a prototype of aminoglycosides?
Tobramycin
What is the mechanism of action of aminoglycosides?
Disrupt bacterial protein synthesis (bactericidal)
Large, positively charged molecules
Not orally absorbed
What are common therapeutic uses of aminoglycosides?
- Serious gram negative infections (ex. Pseudomonas)
- Gram positive infections (combined with bets-lactam)
- Ophthalmic/optic infections (eye or ear drops)
What are drug interactions with aminoglycosides?
- Aminoglycosides + beata-lactams or Vancomycin can increase effectiveness BUT can’t be mixed in IV bag d/t chemical rxn
- Nephrotoxic drugs increase renal damage (ex. Vancomycin, NSAIDs)
What are side effects of aminoglycosides?
- Nephrotoxicity (unreversible)
- Ototoxicity (tinnitus, headache, vertigo)
- Parasthesias, seizures
Increased risk if high trough levels and prolonged duration
What is the dosing and administration of aminoglycosides?
Higher peak = more effective (concentration-dependent killing)
Post-antibiotic effect = washout period = safer
Renal dose adjustment required
PARENTAL, eye/ear drops
What are types of macrolides?
Erythro-
Clarithro-
Azithromycin
What is the mechanism of action for macrolides?
Inhibit bacterial protein synthesis (bacteriostatic)
What are common therapeutic uses for macrolides?
- Respiratory tract infections (ex. Pneumonia)
- Chlamydia, diphtheria
- Alternative to penicillin-allergic pts
What are side effects of Macrolides?
- GI: n/v, diarrhea
- Erythro- and clarithro- inhibit CYP450 enzymes
- Azithro- do not take with Aluminum, Mg2+, Ca2+
- Antagonize effects of clindamycin
What are therapeutic uses for Flourquinolones?
- UTIs
- Pneumonia
- Infection of bones/joints/soft tissue
- Gut infection (travellers diarrhea)
- Opth/optic infections
What are specific drug interactions with Flourquinolones?
Bioavailability decreases with Dairy, antacids, minerals (Ca/Mg/Iron)
What are side effects of Flourquinolones?
- N/v, diarrhea
- Headache, dizziness
- Peripheral neuropathy
- MSK pain
- Tendinitis, tendon rupture
- Cartilage growth suppression
**could lead to c.diff
What is a prototype of Flourquinolones?
Ciprofloxin
“-floxin”
(IV, PO, ear/eye drops)
What is a prototype of Metronidazoles?
Flagyl
PO, IV
What are common therapeutic uses for Metronidazoles?
- C. difficile
- Anaerobic infections of CNS/abdomen/bone/joint/soft tissue/pelvis
- Surgical prophylaxis
- Protazoal infections (the tail- Flagyl!)
What are common side effects of Metronidazoles?
- N/v, diarrhea
- Metallic taste
- Dizziness, vertigo
- Brown urine
What are specific drug interactions with Metronidazoles?
ALCOHOL
Inhibits aldehyde dehydrogenase, leads to build up of acetaldehyde
- headache, n/v, flushing, SOB
What is the mechanism of action for Sulfonamides?
Disrupt folate synthesis do bacteria cannot make DNA/RNA/proteins
What are 2 prototypes of Sulfonamides?
- Sulfamethoxazole
- Trimethoprim (Septra)
(PO, IV)
What are therapeutic uses for Sulfonamides?
- UTIs
2. PCP (pneumocystis carnii pneumonia, AKA Pneumoncystis jiroveci)
What are specific drug interactions with Sulfonamides?
Highly protein bound - displace other drugs
(Warfarin, phenytoin, Sulfonylureas)
**Sulfa allergy
What are side effects of Sulfonamides?
- Hypertensitivity rxn (mild rash fever, photosensitivity)
- Low WBC/platelets
- Hemolytic anemia (rare)
- N/v, diarrhea
- STEVENS-JOHNSON Syndrome
What is the mechanism of action for Clindamycins?
Inhibit bacterial protein synthesis
BACTERIOSTATIC
What are therapeutic uses for Clindamycins?
- Mixed infections
- Skin/soft tissue
- Aspiration pneumonia
- Abdominal/pelvic infections
- Alternative to penicillin
What are common side effects of Clindamycins?
DIARRHEA (lead to C.diff)