Pharmacology - ID 1

What is the principle behind infectious disease pharmacology?

Selective toxicity

What is empiric therapy?

Immediate administration of therapy prior to bacterial identification; based on most likely organism

What is prophylactic therapy?

Prevention of infection in cases of recurrent infections, immunocompromised states, or surgical prophylaxis

What does a bacteriostatic antibiotic do?

Arrests growth and replication of bacteria so immune system can eliminate it

What does a bactericidal antibiotic do?

Directly kills bacteria

What is the Minimum Inhibitory Concentration (MIC)?

The lowest concentration of an antibiotic that inhibits bacterial growth

How much antibiotic concentration is needed to effectively treat infections?

Typically 10x the MIC

Name key patient factors influencing antibiotic choice.

Immune status, renal/hepatic dysfunction, perfusion, age, pregnancy

Which antibiotics use concentration-dependent killing?

Aminoglycosides and fluoroquinolones

What is characteristic of time-dependent killing antibiotics?

Maximal kill based on time above MIC; multiple daily doses

Give examples of time-dependent killing antibiotics.

β-lactams, macrolides, clindamycin, vancomycin

What is the post-antibiotic effect?

Continued bacterial suppression after antibiotic levels drop below MIC

Define narrow-spectrum antibiotics.

Effective against a small group of microorganisms

Define extended-spectrum antibiotics.

Effective against Gram+ and significant Gram- bacteria

Define broad-spectrum antibiotics.

Effective against a wide range of organisms; may disrupt normal flora

Which microbes are Gram-positive cocci?

Staphylococcus (skin infections), Streptococcus (pneumonia, tonsillitis)

What is synergism in antibiotic therapy?

When two antibiotics work better together, e.g., β-lactams + aminoglycosides

Name two genetic causes of antibiotic resistance.

Genetic alterations and altered protein expression

List 3 complications of antibiotic therapy.

Hypersensitivity, direct toxicity, superinfections

What are the three main antibiotic mechanisms?

Cell wall inhibition, protein synthesis inhibition, metabolism inhibition

How do cell wall inhibitors work?

Prevent synthesis or repair of bacterial cell wall

Why are human cells unaffected by cell wall inhibitors?

Human cells lack cell walls

What is the mechanism of action of penicillin?

Interferes with bacterial cell wall synthesis by binding PBPs, inhibiting transpeptidase, and promoting autolysins

What is the antibacterial spectrum of penicillin?

Mainly Gram+ bacteria

What are natural penicillins?

Penicillin G (IV), Penicillin V (PO, more acid-stable)

What are the drugs of choice for gangrene and syphilis?

Natural penicillins

Which penicillins are β-lactamase resistant?

Methicillin, Nafcillin, Oxacillin, Dicloxacillin (Antistaphylococcal PCNs)

What are extended-spectrum penicillins?

Ampicillin, amoxicillin (DOC for Listeria monocytogenes)

Which agents protect amoxicillin from β-lactamase degradation?

Clavulanic acid or sulbactam

Which penicillin has the most potent activity against Pseudomonas?

Piperacillin

Why combine β-lactams with aminoglycosides?

Synergistic killing

Name 3 mechanisms of acquired resistance to penicillin.

β-lactamase production, decreased permeability, altered PBPs

How are most penicillins excreted?

Urinary excretion (dose adjust for renal function)

Are penicillins safe in pregnancy?

Yes, cross placenta but not teratogenic

List 3 adverse effects of penicillin.

Hypersensitivity (rash to anaphylaxis), GI upset (diarrhea), nephritis

Which penicillins may affect coagulation?

Antipseudomonal penicillins

Name a toxicity associated with penicillin salts.

Cation toxicity from Na+ or K+ salts

Which cephalosporins are active against PEcK organisms?

1st gen: Cephalexin (Keflex)

What organisms are added in 2nd gen cephalosporins?

HEN: H. influenza, Enterobacter, Neisseria

Which 3rd gen cephalosporin is given IV/IM?

Ceftriaxone (Rocephin)

Which oral 3rd gen cephalosporin is commonly used?

Cefdinir (Omnicef)

Which generation covers Pseudomonas and Gram+ organisms broadly?

4th gen: Cefepime (Maxipime)

What is unique about ceftaroline?

Only β-lactam effective against MRSA

Which cephalosporin is used for surgical prophylaxis?

Cefazolin

Which cephalosporin has non-renal elimination?

Ceftriaxone (bile and feces)

What is the rate of cross-allergenicity between penicillins and cephalosporins?

3-5%

Which β-lactams are considered to have the broadest spectrum?

Carbapenems (e.g., Imipenem)

What is cilastatin used for?

Prevents nephrotoxic metabolite formation with imipenem

Name a major adverse effect of carbapenems at high doses.

Seizures

Which β-lactam is safe for penicillin-allergic patients?

Aztreonam (monobactam)

What is the spectrum of aztreonam?

Aerobic Gram-negative rods

How do β-lactamase inhibitors work?

Bind and inactivate β-lactamase without intrinsic antimicrobial activity

Give two β-lactam/β-lactamase inhibitor combinations.

Amoxicillin/Clavulanic Acid (Augmentin); Piperacillin/Tazobactam (Zosyn)

What is the MoA of vancomycin?

Inhibits Gram+ bacterial cell wall phospholipid synthesis; bactericidal

What organisms does vancomycin treat?

MRSA, MRSE, Enterococcus (Gram+ only)

What is the oral indication for vancomycin?

C. difficile (PO form stays in GI tract)

How is vancomycin administered?

Slow IV infusion

What are the key adverse effects of vancomycin?

Red man syndrome, ototoxicity, nephrotoxicity

What is daptomycin used for?

Resistant Gram+ infections (MRSA, VRE); not for pneumonia

What are the side effects of daptomycin?

Myalgias, elevated liver enzymes

What is telavancin?

Vancomycin derivative; inhibits Gram+ bacterial cell wall synthesis

What infection is fosfomycin indicated for?

UTIs caused by E. coli or E. faecalis (single-dose treatment)

What is the mechanism of action of polymyxins?

Disrupts Gram- bacterial membranes by acting like a detergent

Which organisms are resistant to polymyxins?

Proteus and Serratia