Anti-infectives

What type of characteristics do beta lactam antibiotics have?

Time-dependent kill characteristics

(maximize duration of time antibiotic concentration remains above MIC to enhance bactericidal effect)

What is the most common and important mechanism of resistance to beta lactam antibiotics?

Bacteria become resistant to β-lactams though the production of β-lactamase enzymes

Function of beta lactamase inhibitors?

β-lactamase inhibitors (clavulanic acid, tazobactam, sulbactam) bind to and inactivate β-lactamase enzymes, which would otherwise destroy β-lactam antibiotics. This allows the antibiotic to remain active and to kill the bacteria.

- Sacrificial substrates only; Do not have an antimicrobial effect

Penicillin ADR and CI (type of beta lactam)?

ADRs: Severe skin reactions (TEN, SJS); renal dysfunction; anemias; numbness/weakness; seizures (high dose) in patients with renal dysfunction

CIs: Hx anaphylaxis; hypersensitivity to PCN/ CEPH

Characteristics of cephalosporins?

- Potential cross-allergenicity w/ PCNs

(likely ~ 1-10%; Lowest in later generation cephs)

- More resistant to β-lactamases enzymes

(Penicillinases - enzyme that inactivates penicillins; Cephalosporinases - enzyme that inactivates cephalosporins)

Adverse effects of Cephalosporin?

Superinfection (C. difficile), Pseudomembranous colitis (Antibiotic-Associated Colitis)

Cephalosporin activity by generation

1st generation Cephalosporins do not have activity against?

Enterococci, MRSA, Bacteroides fragilis, Pseudomonas, Acinetobacter, Enterobacter, Proteus vulgaris, Serratia marcescens

2nd generation Cephalosporins do not cover?

Enterococci, Pseudomonas, MRSA

3rd generation Cephalosporins do not cover?

Enterococci, Anaerobes, MRSA

4th generation Cephalosporins do not cover?

Enterococci, anaerobes, MRSA

4th generation Cephalosporins cause an increase in mortality in patients w/?

Carbapenem resistant gram negative infections

5th generation Cephalosporins are the 1st cephalosporin with activity against?

Multidrug-resistant gram positive organisms - MRSA, vancomycin-resistant S. aureus (VRSA)

Indications for Clindamycin?

Commonly: skin and soft tissue infections: caused by Streptococci, Staphylococci, and anaerobes (used in β-lactam allergy)

Drug to drug interactions of clindamycin?

Erythromycin and Clindamycin (In-vitro

ANTAGONISM)

Do not use in combo

Clindamycin is a class of antibiotics very likely to cause?

C. difficile colitis

Primary use of sulfonamides?

Sulfonamides are used most frequently used with?

Uncomplicated lower UTIs

Trimethoprim (TMP)

How are Carbapenems eliminated?

MOA?

All renally eliminated

(adjusted in renal dysfunction, history of seizure, elderly - seizures)

Vancomycin is the drug of choice for?

How is this administered?

Methicillin-resistant (beta-lactam-resistant) staphylococci (MRSA)

IV - orally (PO) no significant systemic absorption

Adverse drug reactions for Vancomycin?

Too rapid infusion - Red Neck Syndrome (flushing over chest/face, +/- hypotension, and pruritus)

Daptomycin is not to be used for a prescription of?

ADR?

Pneumonia

ADRs: Myopathy/Rhabdomyolysis

Adverse effects of tetracyclines and fluoroquinolones?

ADR: Photosensitivity

Linezolid indications? DDIs?

Hospital-acquired MRSA, MSSA, S.pneumoniae

Tyramine rich foods, adrenergic, SSRI drugs should be avoided due to potential interactions resulting in restlessness, myoclonus, mental status changes

Precautions with fluoroquinolones?

- Direct toxic effects on cartilage and tendon matrix (increased risk in elderly)

- May exacerbate signs of myasthenia gravis, lead to life threatening weakness of respiratory muscles

- Superinfection/Pseudomembranous colitis

Nitrofurantoin indication? ADRs?

Uncomplicated UTI

CrCL < 50 mL/min: AVOID due to inadequate urinary level and potential for toxic serum level

Rare: methemoglobinemia and hemolytic anemia (with G6PD deficiency)

What antibiotics should be prescribed for pharyngitis/tonsillitis?

No PCN allergy – Penicillin or Amoxicillin

Mild PCN allergy - Cephalexin, Cefpodoxime, Cefdinir

What antibiotics should be prescribed for sinusitis?

No PCN allergy – amoxicillin-clavulanate

PCN allergy - Levofloxacin or Doxycycline

What antibiotics should be prescribed for acute otitis media?

No ABX w/in 30 days - Amoxicillin or Amoxicillin Clavulanate

If ABX within 30 days - Amoxicillin Clavulanate

What antibiotics should be prescribed for acute uncomplicated cystitis?

Nitrofurantoin or TMPSMX

What antibiotics should be prescribed for cat and dog bites?

Amoxicillin Clavulanate