unit 10.3: beta-lactam - cephalosporins

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41 Terms

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Cephalosporin
* Derivatives of **7-aminocephalosporanic acid**
* With **2 sites** **of attachment** for various R1 and R2 groups
* More stable to many bacterial β–lactamases, has broader spectrum of activity
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Giuseppe Brotzu
* Isolated Cephalosporin C compound in from the fungus **Acremonium**, previously known as "**Cephalosporium**” in 1945.
* Found in the sea near a sewage outfall in Su Siccu, by Cagliari harbour in Sardinia, Italy
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R group at **7-position**
alters antibacterial activity
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R group at **3-position**
modifies pharmacokinetic profile

* whether they can traverse the blood-brain barrier or not
* hydrophobic or hydrophilic
* biliary or urinary
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* **Cephalexin**
* Cefazolin
* Cefadroxil
* Cephalotin
* Cephradine
* Cephapirin
First generation
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* **Cefuroxime**
* Cefoxitin
* Cefotetan
* Cefamandole
Second generation
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* **Ceftriaxone**
* **Cefotaxime**
* **Cefoperazone**
* **Ceftazidime**
* Cefixime
Third generation
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Cefepime
Fourth generation
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* Ceftaroline
* Ceftolozane
Fifth generation
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Bind to PBPs
### Mechanism of Action

inhibit cell wall synthesis, similar to penicillins
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Structural differences
### Mechanism of Action

___ render them less susceptible to penicillinases produced by staphylococci
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MRSA
### Mechanism of Action

resistant to cephalosporins
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Most are **parenteral**
### Pharmacokinetics

administered or occurring elsewhere in the body than the mouth and alimentary canal.
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renal excretion
### Pharmacokinetics

Major elimination
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hepatic metabolism
### Pharmacokinetics

some with **side chains**
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Cefoperazone and ceftriaxone
### Pharmacokinetics

excreted in the **bile**
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1st- and 2nd-generation
### Pharmacokinetics

Do not enter the CSF when the meninges are inflamed1st- and 2nd-generation
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**1st Gen:** Cefazolin and cephalexin
### Clinical Use

* against G+ cocci, *E coli, K pneumoniae*
* Surgical prophylaxis
* Minimal activity *(Gram (-) cocci, Enterococci. MRSA, Most gram (-) rods)*
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Second Generation
### Clinical Use

* Less activity against gram (+)
* Extended coverage for gram (-)
* Marked differences in activity occur among the drug
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Cefotetan, Cefoxitin
### Clinical Use: *2nd Gen*

* Anaerobic coverage
* B. fragilis
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Cefamandole, cefuroxime, cefaclor
### Clinical Use: *2nd Gen*

H influenzae, M catarrhalis
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Ceftazidime, cefoperazone, cefotaxime

* penetrates BBB except cefoperazone, cefotaxime
### Clinical Use: *3rd Gen*

* Increased activity against **gram (-)** organisms resistant to other beta-lactam drugs
* Ability to **penetrate the blood-brain barrier**
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Ceftriaxone
### Clinical Use: *3rd Gen*

* **gonococcal urethritis** - purulent discharge
* Single injection for acute otitis media
* As effective as 10 days of amoxicillin
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Ceftriaxone (IV) and cefixime
### Clinical Use: *3rd Gen*

Drug of choice for **gonorrhea**
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Cefepime
### Clinical Use: *4th Gen*

* more resistant to beta lactamases
* combines gram positive activity / coverage of 1st gen with wider gram neg
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Ceftaroline
### Clinical Use: *4th Gen*

* active against MRSA that is resistant to Cephalosporins
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rashes to **anaphylactic shock**
### Toxicity

* Allergy
* Complete **cross reactivity** should be assumed
* less frequently than penicillins
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5-10%
### Toxicity: *Allergy*

* **Partial cross reactivity** between penicillin and cephalosporin
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* Pain at **IM injection site**
* **Phlebitis** after IV injection
* Increase **nephrotoxicity** of aminoglycosides
### Toxicity:

Other adverse effects
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Cefamandole, cefoperazone, cefotetan
### Toxicity: *Other adverse effects*

* Drugs containing a **methylthiotetrazole** group
* May cause **hypoprothrombinemia**
* Disulfiram-like reactions with ethanol
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* Listeria
* Atypicals
* Methicillin-resistant staphylococcus aureus (MRSA)- except Ceftaroline
* Enterococcus
Cephalosporins are “**LAME**” because they are inactive against
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Cephalexin
### First Generation:

* effective against **pharyngitis** (above umbilicus infections) which (back then) were mostly gram-positive
* cell wall will be **thicker for gram-positive**
* gram-negative are resistant with beta lactams
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Cefazolin
### First Generation:

* parenteral route (IV)
* longer duration of action, but similar spectrum
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Cefuroxime
### Second Generation:

* given parenterally
* longer half life
* it can cross blood brain barrier
* used for **community-acquired bronchitis & pneumonia**
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Cefuroxime axetil
### **Second** Generation:

* twice daily
* quite resistant even against to beta-lactamase-producing organism
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Ceftriaxone
### **Third** Generation:

* effective against **genital, anal and pharyngeal penicillin-resistant neisseria gonorrhoeae**
* excreted through the **bile**
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Ceftazidine
### **Third** Generation:

* anti-pseudomonal coverage
* **Pseudomonas** are hospital-acquired germ with numerous resistance
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Cefotaxime
### **Third** Generation:

* good choice for infections (bacterial encephalitis & bacterial meningitis)
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Cefepime
### **Fourth** Generation:

* anti-pseudomonal property
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**interstitial nephritis and tubular necrosis**

* if combined with **aminoglycoside** (protein synthesis inhibitor
* cephalosporin don’t go along well w/ aminoglycoside
### Adverse Reactions of Cephalosporins

Renal
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Hypoprothrombinemia and bleeding disorders
### Adverse Reactions of Cephalosporins

Hematologic