Penicillins- drugs, indications, adverse effects, drug interactions,
contraindications, patient teaching, cross-sensitivity.
Beta-Lactam: PCN
Pharmacodynamics
- Inhibit the biosynthesis of peptidoglycan bacterial cel
...
Penicillins- drugs, indications, adverse effects, drug interactions,
contraindications, patient teaching, cross-sensitivity.
Beta-Lactam: PCN
Pharmacodynamics
- Inhibit the biosynthesis of peptidoglycan bacterial cell wall
- Sensitivity
- Natural PCNs: Streptococcus, some Enterococcus strains, some
non–penicillinase-producing Staphylococcus
- Aminopenicillins: greater activity against gram-negative bacteria because of
enhanced ability to penetrate the outer-membrane organisms
- Used for gram-negative urinary and gastrointestinal (GI) pathogens – Escherichia
coli, Proteus mirabilis, Salmonella, some Shigella species, and Enterococcus
faecalis; active against the common gram-negative respiratory pathogens
Moraxella catarrhalis (and Haemophilus influenzae type B)
- Combination with beta-lactamase inhibitors to broaden their spectrum: clavulanate,
sulbactam, tazobactam
Pharmacokinetics
- Well-absorbed from GI tract, but several are unstable in acid: dicloxacillin and amoxicillin
better absorbed than ampicillin
- Bound to proteins with good distribution to most tissues
- Small amount is metabolized; most are excreted as unchanged drug in urine.
- Probenecid prolongs half-life and increases risk for toxicity.
ADR
- May cause serious immediate allergic reactions
- Reactions occur within 2 to 30 minutes of administration.
- Patients may be given desensitization therapy.
- Rash: maculopapular rash occurs 9% of time, is not allergic in origin, and appears 7 to
10 days into treatment.
- GI: diarrhea, nausea/vomiting (n/v); addition of clavulanate increases risk of diarrhea
- Fungal overgrowth
- Clostridium difficile colitis
- Most are pregnancy category B
Clinical use and dosing
- Commonly prescribed for infections seen in primary care
- Amoxicillin: first-line therapy for acute otitis media (AOM) and sinusitis
- PCN: used for streptococcal pharyngitis
- Amoxicillin/clavulanate: first-line therapy for infection following bites, including human
bites
Rational drug selection
- Defining tests (rapid strep) vs empiric method
- Cost
Monitoring
- Patients should return to the office for evaluation of symptom relief.
- Are symptoms getting better?
Patient education Resistance, ADRs, completing course
Cephalosporins- drugs, indications, adverse effects, drug interactions,
contraindications, patient teaching, cross-sensitivity.
Beta-Lactams: Cephalosporins
Pharmacodynamics:
- Structurally and chemically similar to PCNs
- Inhibit mucopeptide synthesis in the bacterial cell wall
Four generations
- First generation
- Used for skin and soft tissue infections
- Primarily active against gram-positive bacteria, S. aureus and S. epidermidis
- Second generation
- Active against same as first generation, plus Klebsiella, Proteus, E. coli
- Third generation
- Used for broader indications
- More active against gram-negative bacteria
- Fourth generation
- Resistant to beta-lactamase
- Primarily active against gram-positive bacteria
- Fifth generation Ceftaroline
- Similar to third generation, except active against methicillin-resistant S. aureus
(MRSA)
Pharmacokinetics: oral formulations absorbed from GI tract, widely distributed to most tissues,
some highly bound to proteins, some are metabolized to less active compounds, most excreted
via kidneys in various degrees as unchanged drug
ADR: allergies, skin rashes, arthralgia, coagulation abnormalities, anemia, neutropenia,
leukopenia, thrombocytosis, fever, seizures, renal/hepatic failure
Clinical use and dosing
- Used for therapeutic failure in AOM
- First generation: streptococcal pharyngitis, skin infections
- Cephalexin, cefpodoxime, cefixime: can be prescribed as second-line drugs for urinary
tract infection (UTI)
- Ceftriaxone and cefixime: used for general condition in Gonococcus (GC)/Chlamydia
infection
- Cefpodoxime, cefuroxime, or parenteral ceftriaxone fol
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