First-generation cephalosporins

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Chapter: Medicinal Chemistry : Antibiotics

i. Cephalexin (Keflex, Keforal) ii. Cefadroxil (Cefadrox, Droxyl, Codroxil) iii. Cephalothin (Keflin) iv. Cefsulodin v. Cephradine


Cephalosporins - Synthesis and Drug Profile

First-generation cephalosporins

 

i. Cephalexin (Keflex, Keforal)


Synthesis


Properties and uses: Cephalexin monohydrate is a white crystalline powder, sparingly soluble in water, and practically insoluble in alcohol. The α-amino group of cephalexin renders it acid stable. The 3-methyl group is responsible for the metabolic stability. It is particularly recommended for urinary tract infection.

Dose: The oral dose for adults is 250–500 mg every 6 h, for children, the dose is 18–25mg/kg every 6 h.

Assay: It is assayed by adopting liquid chromatography technique.

Dosage forms: Cefalexin capsules I.P., B.P., Cefalexin oral suspension I.P., B.P., Cefalexin tablets I.P., B.P.

 

ii. Cefadroxil (Cefadrox, Droxyl, Codroxil)


Synthesis


Properties and uses: Cefadroxil monohydrate is a white or almost white powder, slightly soluble in water, and sparingly soluble in ethanol. The antibacterial spectrum of action and therapeutic indications of cefadroxil are very similar to those of cephalexin and cephradine. The D-p-hydroxyphenylglycyl isomer is much more active than the L-isomer.

Assay: It is assayed by adopting liquid chromatography technique.

Dosage forms: Cefadroxil capsules I.P., B.P., Cefadroxil oral suspension I.P., B.P. Cefadroxil tablets I.P.

Dose: In the case of uncomplicated lower urinary tract infections: For adults, the dose is 1–2 g daily as a single or 2 divided doses. For children more than 6 years, the dose is 500 mg twice a day, that is, 1–6 years, 250 mg twice a day; for children less than 1 year, the dose is 25 mg/kg daily in divided doses. In the case of skin and skin structure infections: For adults, the dose is 1g per day in single or divided doses. For children, the dose is 30 mg/kg per day in equally divided doses every 12 h. In the case of pharyngitis and tonsilitis: For adults in the treatment of group A beta-haemolytic streptococcal pharyngitis and tonsilitis, the dose  is 1 g per day in single or divided doses for 10 days. In the case of children, 30 mg/kg per day in equally divided doses every 12 h for at least 10 days.

 

iii. Cephalothin (Keflin)


Synthesis


Properties: Cephalothin is a white, odourless, crystalline powder, insoluble in most organic solvents, soluble in organic solvents and it is acid stable. It is hygroscopic and decomposes on heating, and it has been described as broad-spectrum antibacterial compound, it is not in the same class as the tetracyclines. Its spectrum of activity is broader than that of penicillin G and more similar to that of ampicillin.

Dose: The dose for adults given IM or IV is equivalent to 500 mg–1 g every 4 to 6 h; children the dose is 13–26 mg/kg of body weight every 4 h.

 

iv. Cefsulodin


Synthesis


Properties and uses: It is indicated for use in staphylococcal and pseudomonal infections.

 

v. Cephradine


Synthesis

Route-I.


Route-II. From: 2-Amino-2-phenylacetic acid


Properties and uses: Cephradine exists as colourless crystals, soluble in propylene glycol, but slightly soluble in acetone or alcohol. Used as an antibacterial agent.

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