Penicillin physicochemical properties

Specialized antibiotic formulations have been developed for DCT, with physicochemical properties chosen to confer prolonged retention in the mammary secretions (21,, ). Ziv ( ) has summarized the desirable kinetic and other properties of such a product. The following antibiotic formulations are presently approved by the U.S. Center for Veterinary Medicine, FDA for infusion into the dry mammary gland erythromycin (300 mg), oxytetracycline-HCl (426 mg), benzathine cloxacillin (500 mg), cephapirin benzathine (300 mg), novobiocin (400 penicillin (200,000 lU) novobiocin (400 mg), penicil-... 

Until 1944, it was assumed that the active principle in penicillin was a single substance and that variation in activity of different products was due to the amount of inert materials in the samples. Now we know that during the biological elaboration of the antibiotic, several closely related compounds may be pnxtuced. These compounds differ chemically in the acid moiety of the amide. side chain. Variations in this moiety produce differences in antibiotic effect and in physicochemical properties, including stability. Thus, one can speak of penicillins as a group of compounds and identify each penicillin specincally. As each of the different penicillins was first isolated, letter designations were used in the United States the British used Roman numerals. 

The chemical nature and related physicochemical properties largely govern the distribution and elimination, which refers to biotransformation (metabolism) and excretion, of antimicrobial agents. The majority of antimicrobial agents are weak organic electrolytes, either weak acids (penicillins, cephalosporins, sulphonamides) or weak bases (aminoglycosides, lincosamides, macrolides, diaminopyrimidines, metronidazole), while fluoroquinolones, tetracyclines and rifampin are amphoteric compounds, and chloramphenicol and its... 

Rollo IM, Physicochemical properties of some semisynthetic penicillins. Can. /. Physiol. Pharmacol., 50,976-985 (1972) cited in N K. 

These and other physicochemical properties of cephalosporins and penicillins have been adeptly reviewed (Sweet, 1973 Gorman and Ryan, 1973 Demarco and Nagarajan, 1973). The present chapter will concentrate mainly on subsequent literature and, in particular, dwell on the role of theoretical calculations in elucidating the properties of the p-lactams. 

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