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Healthcare Communications

Cefadroxil



Cephalosporins





The basic nucleus of the cephalosporins is 7 amino cephalosporanic acid. This is composed of a ß-lactam ring and a dihydrothiazine ring



Cephalosporins

First
generation
Second generation
Third
generation
Cephalothin
Cefamandole
Cefotaxime
Cefazolin
Cefoxitin
Moxalactam
Cephapirin
Cefuroxime
Cefoperazone
Cephradine
Cefaclor
Ceftizoxime
Cephalexin  
Ceftriaxone
Cefadroxil  
Ceftazidime
   
Cefsulodin
   
Cefmenoxime
   
Cefixime

 

Cephalosporins - Spectrum

Relative antibacterial coverage of cephalosporins by generation

Generation gm +ve gm -ve
First generation +++ +
Second generation ++ ++
Third generation + +++

 

 

The OH group makes the difference!

The addition of the para-hydroxyl group (OH) on the aromatic ring of cephalexin alters the pharmacokinetic properties of cephalexin and creates the new drug, cefadroxil

 

Cefadroxil

Mechanism of Action
- Bactericidal
- Act by inhibition of bacterial cell wall synthesis



Spectrum

Similar to cephalexin

Important organisms
Staph. aureus
Strep. pyogenes
Strep. pneumoniae
E. coli
Proteus mirabilis
Klebsiella pneumoniae
H. influenzae



Pharmacokinetics

Cefadroxil is superior to cephalexin because of better pharmacokinetics.

These include
- Higher serum concentrations
- Better lipid solubility results in better penetration into body tissues and fluids
- Slower excretion, hence longer duration of action - Higher AUC (area under plasma concentration - time curve)



Absorption

Cefadroxil is well absorbed on oral administration; food does not interfere with the absorption

Distribution

- Better lipid solubility than cephalexin facilitates superior penetration into body tissues and fluids. - Good concentrations in tonsils, lungs, bone, muscle, synovial capsule, prostate, gynaecological tissues and body fluids including sputum, pleural fluid, skin blisters and aqueous humour

 

Metabolism & Excretion

- Cefadroxil is not metabolised in the body
- Excreted unchanged in urine
- Plasma half-life 1-1.5 hours; twice that of cephalexin

Indications

1. Lower Respiratory Tract Infections
2. Pharyngitis
3. Otitis media
4. Skin & Soft Tissue Infection
5. Bone & Joint Infection
6. Urinary Tract Infection
7. Prostatitis
8. Biliary Tract Infection



Dosage

Usual dosage for adults
500 mg twice daily

Children
30-50 mg/kg/day in divided doses

Renal Failure
- Creatinine clearance 10-25 ml/min
administer dose every 24 hours

- Creatinine clearance 0-10 ml/min
administer dose every 36 hours


Adverse Effects

- Uncommon
- Nausea, vomiting, diarrhoea, allergic rashes
may occur
- Safe in pregnancy

Contraindications
- Hypersensitivity



Salient Features

- Broad antibacterial spectrum
- Resistant to inactivation by b-lactamases
- Good GI absorption
- High and prolonged concentration in plasma, urine, body tissues and fluids
- Widely distributed; better tissue penetration than cephalexin
- Long plasma half life
- Prolonged duration of action
- Convenient twice daily dosing
- Well tolerated

 




Advantages over Cephalexin

- Similar antibacterial spectrum
- Superior and more prolonged tissue concentrations
- Convenient b.d. dosing compared to q.I.d. dosing with cephalexin
- Better compliance with simpler dosing may result in greater efficacy

 

Advantages over penicillins
(Ampicillin, Amoxycillin)

- Effective against organisms resistant to penicillins
- May be tried in patients who are hypersensitive to penicillins

 


Advantages over fluoroquinolones
(Ciprofloxacin, Norfloxacin)

- Fluoroquinolones are chiefly indicated for gram negative infections; cefadroxil may be preferred for gram positive infections
- Cefadroxil is safe in children and in pregnancy; fluoroquinolones are better avoided here