Penicillin phenoxymethylpenicillin

The only penicillins used in their natural form are benzylpenicillin (penicillin G) and phenoxymethylpenicillin (penicillin V). The remainder of penicillins in clinical use are derived from 6-APA and most penicillins having useful biological properties have resulted from acylation of 6-APA using standard procedures. 

The chemical structures of phenoxymethylpenicillin (penicillin V) and flucloxacillin are shown in Figure A12.1. 

Figure A12.1 Phenoxymethylpenicillin (penicillin V) (left) and flucloxacillin (right).

In 1954, however, Brandi and Margreiter (65) reported that biosynthetic phenoxymethylpenicillin (penicillin V) was superior to benzyl-penicillin in terms of acid stability. Since this compound retains good activity against penicillin-sensitive gram-positive bacteria penicillin V quickly gained acceptance as the only reliable penicillin for oral administration. 

Guar gum 5 g (Guarem, 95% guar gum) reduced the absorption of a single 1980-mg dose of phenoxymethylpenicillin (penicillin V) in 10 healthy subjects. Peak serum penicillin levels were reduced by 25% and the AUCo 6 was reduced by 28%. The reasons are not understood. 

The absorption of amoxicillin may be significantly reduced when given with or 2 hours after acacia. Guar gum causes a small reduction in the absorption of phenoxymethylpenicillin (penicillin V). 

In one analysis of patients taking warfarin with antibacterials, there was no association between use of penicillins (phenoxymethylpenicillin (penicillin V) and broad-spectrum penicillins) and an increase in DSTR. The estimated change in DSTR was 0.117 in 109 patients given the combination. ... 

The penicillins and cephalosporins, collectively known as beta-lactam antibiotics, are among the most widely used and valuable antibiotics currently available. Ben-zylpenicilhn (penicillin G) and phenoxymethylpenicillin (penicillin V) are derived from Penicillium molds by fermentation, while half-synthetic penicillins are derived by chemical modification of the penicillin nucleus, 6-aminopenicillanic acid (6-APA), itself obtained either by splitting the side chain from benzylpenicillin through an enzymatic process or via a chemical deacylation reaction. 

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