Beta Lactam Antibiotics Flashcards
What does the main structure of the beta lactam consist of?
How do they work?
consist of the beta-lactam ring, essential for the activity of the antibiotic against a pathogen.
Most β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism.
Struture of penicillins?
3
thiazolidine ring,
beta-lactam ring,
a secondary amino group on the beta-lactam ring where substituents can attach to form different compounds
MOA of Penicillin?
3
- Bactericidal to growing bacteria
- Interferes with transpeptidation of cell wall synthesis
- cell wall is destroyed and the bacterial cell dies
What do beta lactam bacteria bind to?
bind to a family of related enzymes that are called—penicillin binding proteins (PBPs)
What do beta lactam antibiotics bind to?
the PBPs and inhibit transpeptidation which stops the cross-linking of polysaccharides
What step is inhibited by beta-lactam antibiotics?
the linear
polymers are being
cross-linked by
transpeptidation
HOw do Bacteria often develop resistance to β-lactam antibiotics ?
synthesizing β-lactamase (penicillinase), an enzyme that breaks down the beta-lactam ring and inactivates the antibiotic (essentially this is metabolism of the drug)
How do we overcome Beta-lactam resistance?
β-lactam antibiotics are often given with β-lactamase inhibitors such as clavulanic acid.
What are the Beta-Lactam Compound classes?
3
Penicillins
Cephalosporins
Beta-Lactamase Inhibitors- combined w/ PCN’s
Penicillin classifications?
3
Penicillin G
Antistaphlococcal PCNs
Broad Spectrum PCNs
NAme the types of Antistaphlococcal PCNs?
4
nafcillin,
dicloxacillin,
oxacillin,
cloxacillin
What are the types of broad spectrum PCNs?
Second generation
Third generation
Fourht generation
What are some second generaton broad spectrum pcns?
2
ampicillin, amoxicillin
What are some of the third generation broad spectrum pcns?
2
carbenicillin, ticarcillin
Fourth generation broad spectrum pcns?
piperacillin
Combinations w/ beta-lactamase inhibitors?
4
- amoxacillin/potassium clavulanate (Augmentin)
- ampicillin/sulbactam (Unasyn) -broader coverage-sicker pts
- Ticarcillin/potassium clavulanate (Timentin)
- Piperacillin & tazobactam sodium (Zosyn)
All PCNs should be given on an empty stomach except which one?
oral amoxacillin
Giving PCNs with probenecid (500mg q 6 hrs) does what?
increases blood levels of all PCNs
Allergic reactions to one PCN will be what to others?
What can these reactions range from?
cross reactive to others,
reactions can be urticarial to anaphylaxis to serum sickness
PCNs can cause what complications?5
These are rare but mainly seen with what?
encephalopathy: somnolence, stupor, coma, seizures; (NEUROTOXICITY) rare, mainly seen with high doses
What side effect is the most frequent complaint with PCNs?
GI reactions, especially diarrhea
What GI complication do we have to worry about with all antibiotics?
C.Diff
What is the use of Penicillin G?
6
Treatment of infections (including 1. sepsis, 2. pneumonia, 3. pericarditis, 4. endocarditis, 5. meningitis, 6. anthrax caused by susceptible organisms
What groups of bacteria is Penicillin G active against?
4
Penicillin VK/oral form is the drug of choice for which infections?
- Gram-positive cocci (streptococci, staphylococci)
- Gram-positive rods (Listeria, actinomyces)
- Gram-negative cocci (Neisseria)
- Most anaerobes (clostridium)
strep pharyngitis
What are the dosage form of Penicillin G?
Which ones do we want to use the most?
IM
IV
PCN VK is oral form (has poor bioavailability, narrow spectrum)
What are the IM forms of Penicillin G?
How long does one injection last?
Name two infections that its used for and one that is now resistant?
Name two infections that the IV form of penicillin G is used to treat?
PCN G benzathine & *PCN G procaine
10-12 days
strep and sometimes syphilis
(gonorrhea is now resistant)
IV form used to treat meningitis and endocarditis
How would we treat Erysipelas with penecillin G?
How would we treat Neurosyphilis with penicillin G?
In general IV penecillin G?
(how much and how often)
IV: 1-2 million units every 4-6 hours x 7-10 days
IV: 18-24 million units/day in divided doses every 4 hours (or by continuous infusion) for 10-14 days
1-24 million units/day divided every 4-6 hours
Pregnancy category for Penicillin G?
Safe for lactation?
Renal dosing?
Hepatic dose?
B (presumed safety based on animal studies)
Yes
Adjust dose for creatinine clearance
Local adverse rxn for penicillin G?
Significant adverse reactions to penicillin G?
Local: Injection site reaction
- Cardiovascular: Localized phlebitis, local thrombophlebitis
- Central nervous system (high doses): Coma, hyperreflexia, myoclonus, seizure
- Dermatologic: Contact dermatitis, skin rash
Endocrine & metabolic: Electrolyte disturbance (high doses) - Gastrointestinal: Pseudomembranous colitis
- Hematologic & oncologic: Neutropenia, positive direct Coombs test (rare, high doses)
- Hypersensitivity: Anaphylaxis, hypersensitivity reaction (immediate and delayed), serum sickness
- Immunologic: Jarisch-Herxheimer reaction
- Renal (high doses): Acute interstitial nephritis, renal tubular disease
Cardiovascular CNS Dermatologic Endocrine and metabolic GI Hematologic Hypersensitivity Immunologic Renal
Contraindications for Penicillin G?
Hypersensitivity to penicillin or any component of the formulation
Warnings and precautions for Penicllin G?
6
- Anaphylactoid/hypersensitivity reactions
- Superinfection
- Disease-related concerns
- Seizure disorders
- Special populations: 6. Pediatrics/Neonates will have decreased renal clearance of PCN
Drug interactions with Penicillin G?
7
BCG : Causes Dimish Effect Risk X: Avoid combination
Methotrexate: Increase Effect. Risk C: Monitor therapy
Probenecid: Increase Effect. Risk C: Monitor therapy
Sodium Picosulfate: Dimish Effect. Management: Consider using an alternative product for bowel cleansing prior to a colonoscopy in patients who have recently used or are concurrently using an antibiotic. Risk D: Consider therapy modification
Tetracycline Derivatives: Dimish Effect. Risk D: Consider therapy modification
Vitamin K Antagonists (eg, warfarin): May enhance effect. (monitor INR)
OBCP’s: pcn may decrease contraceptive efficacy
BCG Methotrexate Probenecid Sodium Picosulfate Tetracycline Derivatives Vitamin K Antagonists (eg, warfarin) OBCP’s
Antistaphylococcal PCNs
use and activity?
2
WHo is it inactive against? 2
Name the three exmaples given of Antistaphylococcal PCNs?
semisynthetic PCNs used for infection with
- beta-lactamase-producing staph, also used against
- PCN susceptible strains strep & pneumococci
Inactive against Enterococci &; methicilliin resistant strains (MRSA)
Dicloxacillin,
oxacillin, and
nafcillin
(antibiotics that are not affected by beta-lactamase enzyme)