Diarrhoea ampicillin

Amoxycillin is a semisynthetic penicillin, a close congener of ampicillin and active against gram positive and negative organisms. Its absorption is more complete than ampicillin. Food does not interfere with its absorption. Its absorption after oral administration is complete hence less incidence of diarrhoea. It is eliminated in urine in unchanged form. 

Amoxicillin (t) 1 h previously known as amoxycillin) is a structural analogue of ampicillin (below) and is better absorbed from the gut (especially after food), and for the same dose achieves approximately double the plasma concentration. Diarrhoea is less frequent with amoxicillin than with ampicillin. The oral dose is 250 mg 8-hourly a parenteral form is available but offers no advantage over ampicillin. For oral use, however, amoxicillin is preferred because of its greater bioavailability and fewer adverse effects. 

Adverse effects. Ampicillin may cause diarrhoea but the incidence (12%) is less with amoxicillin. Ampicillin and amoxicillin are the commonest antibiotics to be associated with Clostridium difficile diarrhoea, although this is related to the frequency... 

Amoxycillin differs only in one hydroxyl group from ampicillin. It is absorbed about twice as efficiently as the latter antibiotic. Evidence is accumulating that the incidence of skin eruptions is about half that reported for ampicillin (28 —31 ). The overall incidence of skin rash and/or urticaria reported in studies involving over 4000 patients has been 3% (29 ). It is also obvious from the literature cited here that the incidence of diarrhoea with amoxycillin (2—4%) is lower than with ampicillin (11%) (SED VllI, p. 563). However, a very recent report does describe a case in which a typical (and histologically verified) pseudomembranous colitis occurred in a boy aged 10 shortly after a brief course of treatment with amoxycillin (250 mg 3 times daily). No other apparent causal factor was in evidence (80 ). Two cases have been described of rash after amoxycillin in patients with infectious mononucleosis (32 ). 

Pivampicillin, the pivaloylester of ampicillin, relatively often gives rise to upper gastrointestinal intolerance, especially when not taken with food an incidence of 11% is reported (31, 33 ). The frequency of diarrhoea is, however, less than with ampicillin, probably due to better resorption. 

Talampicillin is the phthalidylester of ampicillin (83 " ). It has been designed, as was pivampicillin, to obtain enhanced resorption. The ester is rapidly hydrolyzed in vivo. The serum levels are reported to be twice as high as those after equivalent dosages of ampicillin. In comparative trials the frequency of talampicillin-associated diarrhoea was approximately half that observed... 

Ampicillin has also been thought to reduce the effect of oral contraceptives. Here, however, the evidence is much weaker than with the other drugs mentioned above. Pregnancies were reported (122 ) to have occurred in 3 patients taking oral contraceptives while on ampicillin. In no case was there any failure of compliance to the regimen, nor did any patient suffer from diarrhoea or vomiting as a result of the ampicillin treatment. 

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