Cefazolin

Absorption

Not absorbed from GI tract. Must be administered parenterally. Peak serum concentrations attained 1-2 hours post intramuscular injection.

Description

Cefazolin has the natural acetyl side chain at C-3 replaced by a thio-linked thiadiazole ring. Although this group is an activating leaving group, the moiety is not subject to the inactivating host hydrolysis reaction that characterizes cephapirin. At C-7, it possesses a tetrazoylmethylene unit. Cefazolin is less irritating on injection than its cohort in this generation of drugs and has a longer half-life than cephapirin. Its dosing should be reduced in the presence of renal impairment. It is comparatively unstable and should be protected from heat and light.

Chemical properties

needles

Originator

Cefamedin,Fujisawa,Japan,1971

The Uses of Cefazolin

Cefazolin is an antibacterial compound derived from 7-amino-cephalosporanic acid.

The Uses of Cefazolin

Antibacterial (systemic).

Background

A semisynthetic cephalosporin analog with broad-spectrum antibiotic action due to inhibition of bacterial cell wall synthesis. It attains high serum levels and is excreted quickly via the urine.

Indications

Mainly used to treat bacterial infections of the skin. It can also be used to treat moderately severe bacterial infections involving the lung, bone, joint, stomach, blood, heart valve, and urinary tract. It is clinically effective against infections caused by staphylococci and streptococci species of Gram positive bacteria. May be used for surgical prophylaxis; if required metronidazole may be added to cover B. fragilis.

What are the applications of Application

Cefazolin is a semisyntheti cephalosporin analogue

Definition

ChEBI: A cephalosporin compound having [(5-methyl-1,3,4-thiadiazol-2-yl)sulfanyl]methyl and (1H-tetrazol-1-ylacetyl)amino side-groups.

Manufacturing Process

7-Aminocephalosporanic acid is converted to its sodium salt and acylated with 1H-tetrazole-1-acetyl chloride. The acetoxy group is then displaced by reaction with 5-methyl-1,3,4-thiadiazole-2-thiol in buffer solution. The product acid is converted to the sodium salt by NaHCO3.

Therapeutic Function

Antibacterial

Antimicrobial activity

Enterobacter, Klebsiella, Providencia, Serratia spp. and Pr. vulgaris are all resistant. B. fragilis is resistant, but other anaerobes are susceptible.

Pharmacokinetics

Cefazolin (also known as cefazoline or cephazolin) is a semi-synthetic first generation cephalosporin for parenteral administration. Cefazolin has broad-spectrum antibiotic action due to inhibition of bacterial cell wall synthesis. It attains high serum levels and is excreted quickly via the urine.

Pharmacokinetics

Distribution
The volume of distribution is the smallest of the cephalosporins in group 1, perhaps an indication of relative confinement to the plasma space. It crosses inflamed synovial membranes, but the levels achieved are well below those of the simultaneous serum levels and entry to the CSF is poor. In patients receiving 10 mg/kg by intravenous bolus, mean concentrations in cancellous bone were 3.0 mg/kg when the mean serum concentration was 33 mg/L, giving a bone:serum ratio of 0.09. Some crosses the placenta, but the concentrations found in the fetus and membranes are low.
Metabolism and excretion
It is not metabolized. Around 60% of the dose is excreted in the urine within the first 6 h, producing concentrations in excess of 1 g/L. Excretion is depressed by probenecid. The renal clearance is around 65 mL/min and declines in renal failure, when the half-life may rise to 40 h, although levels in the urine sufficient to inhibit most urinary pathogens are still found. It is moderately well removed by hemodialysis and less well by peritoneal dialysis.
Levels sufficient to inhibit a number of enteric organisms likely to infect the biliary tract are found in T-tube bile (17–31 mg/L after a 1 g intravenous dose), but this is principally due to the high serum levels of the drug and the total amounts excreted via the bile are small.

Clinical Use

Cefazolin has been widely used in surgical prophylaxis, especially in biliary tract (because of the moderately high concentrations achieved in bile), orthopedic, cardiac and gynecological surgery.

Side Effects

Side effects are those common to other cephalosporins ,including rare bleeding disorders and encephalopathy in patients in whom impaired excretion or direct instillation leads to very high CSF levels. Neutropenia has been described and hypoprothrombinemic bleeding has been attributed to the side chain.

Synthesis

Cefazolin, (6R-trans)-3[[(5-methyl-1,3,4-thiadiazol-2-yl)thio]methyl]-8-oxo- 7-[(1H-tetrazol-1-ylacetyl)amino]-5-thia-1-azabycyclo[4.2.0]oct-2-en-2-carboxylic acid (32.1.2.7), is synthesized by reacting 7-aminocephalosporanic acid with a mixed anhydride (32.1.2.6), which is the result of a reaction of tetrazolylacetic acid with pivalic (trimethylacetic) acid chloride. Further reaction with 2-mercapto-5-methyl-1,3,4-thiadiazole results in a substitution of the 3-acetoxy group with a mercaptothiadiazol group, giving cefazolin (32.1.2.7).

Metabolism

Not metabolized.