ANTIMICROBIL AGENTS AND CHEMOTHERAPY, Apr. 197, p. 358-36 Copyright 197 Aerican Society for Microbiology Vol. 1, No. 4 Printed in U.S.A. Aoxicillin: In Vitro and Pharacological Studies GERALD P. BODEY AND JANE NANCE Departent ofdevelopental Therapeutics, The University of Texas M. D. Anderson Hospital and Tuor Institute at Houston, Houston, Texas 7705 (Received for publication 4 January 197) Aoxicillin is a new seisynthetic penicillin which is active in vitro against grapositive cocci (except penicillin G-resistant Staphylococcus aureus) and ost isolates of Proteus irabilis and Escherichia coli. Its in vitro activity is quite siilar to apicillin, but it produces higher seru levels after oral adinistration. The ean peak seru levels of aoxicillin in 11 noral volunteers were.30 pag/l after 15 g, 3.43 JAg/l after 50 g, 6.75 jug/l after 500 g, and 9.90 ;&g/l after 1 g. About 70% of the drug was excreted in the urine during the first 6 hr. The ability to synthesize derivatives of penicillin Beecha, Inc., Clifton, N.J.), apicillin (supplied by G was a ajor advance in antibiotic therapy. The Bristol Laboratories Syracuse, N.Y.), and cephalothin discovery of apicillin broadened the spectru (supplied by Eli Lilly & Co., Indianapolis, Ind.). The of activity of penicillins to include soe granegative bacilli. Recently, attepts have been antibiotics were diluted in either tryptose phosphate or Mueller-Hinton broth to a final concentration of 00,Ag/l. Twofold serial dilutions of the antibiotics ade to iprove the absorption of apicillin by were ade with broth, using 50-,Aliter saples, and odifying its structure. Aoxicillin (a-aino-phydroxybenzylpenicillin, BRL-333) is a new terined after incubation at 37 C for 18 hr. All studies the inial inhibitory concentration (MIC) was de- seisynthetic penicillin with antibacterial activity were perfored in triplicate. siilar to apicillin (Fig. 1; see references 7 and The organiss used in this study were cultured fro 10). However, the drug is ore effective than speciens obtained fro patients between January apicillin for the treatent of experiental infections in ice and results in substantially higher group A beta-heolytic streptococci, 19 isolates of 1967 and Noveber 1971. A total of 58 isolates of seru levels in huans (1,, 8). This report describes the results of in vitro susceptibility testing coli, and 5 isolates each of Serratia arcescens, Diplococcus pneuoniae, 49 isolates of S. aureus, 50 isolates of Proteus spp., 100 isolates of Escherichia with aoxicillin and the seru levels achieved in Pseudoonas aeruginosa, Klebsiella spp. and Enterobacter spp. were studied. noral volunteers after oral adinistration of this drug. Clinical pharacological studies were conducted in 11 noral volunteers ranging in age fro 0 to 36 MATERIALS AND METHODS years old and weighing fro 106 to 18 lb. Infored Susceptibility tests were perfored with 376 clinical consent was obtained fro each subject according to isolates of gra-positive cocci and gra-negative institutional policies. All of the subjects had noral bacilli using a icro-dilutor (5). Isolates of Staphylococcus aureus were inoculated into tryptose phosphate pyruvic transainases, alkaline phosphatase, and values of seru creatinine, glutaic oxaloacetic and broth, and isolates of group A beta-heolytic streptococci and pneuococci were inoculated into tryp- days between studies in the sae individual. blood-urea nitrogen. There was an interval of at least tose phosphate broth containing % huan blood Studies were conducted with aoxicillin (supplied by (9). After incubation at 37 C for 18 hr, a 0.1-l saple of this broth containing organiss was added to Beecha, Inc., Clifton, N.J.) and apicillin (supplied Beecha-Massengill Pharaceuticals, Division of 9.9 l of tryptose phosphate broth, and a 50-,uliter by Bristol Laboratories, Syracuse, N.Y.). The drugs saple was used as the inoculu for susceptibility were adinistered orally after an overnight fast. testing. The tryptose phosphate broth used for streptococci and pneuococci contained 1.5% huan tion of the antibiotic, and at 30 in and 1,, 3, 4, and Blood speciens were obtained prior to adinistra- blood. All gra-negative bacilli were inoculated into 6 hr after adinistration of the antibiotic. Urine was Mueller-Hinton broth. After incubation at 37 C for collected before adinistration of the antibiotic and 18 hr, a 10-5 dilution was ade in Mueller-Hinton during the study period. In the study of the effect of broth, and a 50-pliter saple was used as the inoculu for susceptibility testing. The total volue in each dose was given 1 hr before aoxicillin and every 6 hr probenecid on the seru levels of aoxicillin, a 0.5-g well was 100,Aiters. for a total of three doses. The antibiotics studied were aoxicillin (supplied Antibiotic concentrations were deterined by using by Beecha-Massengill Pharaceuticals, Division of an agar well ethod with Sarcina luiea NCTC 8340 358
VOL. l, 197 AMOXICILLIN 359 as the test organis. The organis was inoculated on a slant of antibiotic ediu % 1 (Difco) and incubated at 37 C for 18 hr. A suspension of the organis was ade by washing the slant with 5 l of noral saline, and additional saline was added so that the suspension had an absorbance of 1.96 at a wavelength of 650 n. A 0.1-l saple was added to 65 l of antibiotic ediu # 1 (Difco), and the edia was poured into plates. Wells (0.75- diaeter by 0.75- deep) were cut into the agar. The wells were filled with 0.1 l of the speciens, and the plates were incubated at 37 C for 18 hr. Dilutions of the speciens were ade Cheical Structure Of Aoxicillin Copared To Apicillin O s CH3 HO CH -C-NH -CH -CH C -. CH3 NH N CH -COOH AMOXICILLIN (a aino-p-hydroxybenzylpenici llin) *1 C 0 II s -CH3 CH -C--NH- CH-CH C I CH3 NH C-N CH -COOH 0O AMPICILLIN FIG. 1. Cheical structure of aoxicillin o apicillin. copared Eci : Cf) LLI.:x -j C) In LL. l--.m LU C-> cr- LU CL -CZ -i 100 / I 80 60 40 0 in pooled huan seru or urine so that zone sizes fell within the standard curve. Zones of inhibition were easured and copared to a standard curve. The standard curve was deterined by dissolving aoxicillin standard in pooled huan seru or urine to final concentrations of 0.1, 0.5, 0.50, and 1.0,Ag/l and easuring zones of inhibition after incubation at 37 C for 18 hr. All deterinations were perfored in triplicate. The standard error of the ean was calculated by the ethod of Mantel (6). The 95% confidence liits were deterined as twice the standard error of the ean. RESULTS The antibacterial activity of aoxicillin is illustrated in Fig.. The drug was especially active against group A beta-heolytic streptococci, pneuococci, and penicillin G-susceptible S. aureus. Only 8% of isolates of S. aureus resistant to 50 M4g of penicillin G per l were susceptible to aoxicillin at this concentration or less, and none were susceptible to less than 1.5,g/l. Seventy-six per cent of P. irabilis isolates were susceptible to 1.56,ug or less of aoxicillin per l, but 0% were resistant to 1.5 Ag/l or ore. Fifty-seven per cent of E. coli isolates were susceptible to 6.5,ug/l or less, but ost of the reaining isolates were resistant to 50,ug/l or ore. Only a few of the other gra-negative bacilli were sensitive to aoxicillin. The activity of aoxicillin was copared to that of apicillin and cephalothin (Fig. 3). Aoxicillin was slightly ore active than apicil- ACTIVITY OF *AMOXICILLIN IN VITRO 0.003 0.013 0.05 0.0 0.78 3.1 1.5 50 00 MINIMUM INHIBITORY CONCENTRATION (g/l) FIG.. Activity of aoxicillin in vitro against clinical isolates ofgra-positive cocci and gra-negative bacilli. The nuber in parentheses refers to the nuber of isolates tested.
360 BODEY AND NANCE ANTIMICROB. AG. CHEMOTHER. Activity Of Aoxicillin Copared To Apicillin And Cepholothin K,eF s e' -Grre-r~bbuer 5errot (75),1 Stoph oureus (49! Pneurnc cc C s5o() / C- r, C) LJ <1 z 0 ir z n 60 4 v1 0 0-100 - 80 60-40 - 0 - n I /,1 Eco,,10) 00 078 31 1 5 50 00 / ii1 /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I -i "I I''= 1,' I / 1 / I,. Proteus Spp (50) _ji / 0.013 0 05 0.0 0.78 3.1 15 5C 00 0003 0013 005 00 MINIMUM INHIBITORY CONCENTRATION (jug/l) FIG. 3. Coparison of the in vitro activity of aoxicillin, apicillini, anid cephalothini. Seru Levels Following The Oral Adinistration Of 15g. And 50g. Of Aoxicillin FIG. 4. Mean seru levels following the oral adinistration of 15-g and 50-g doses of aoxicillin to 11 noral volunteers. The bars indicate the 95% confidence liits. -E -3..:I P-' U.j I C.) cr V)ui 8-7- 6-5- 4 3- -71 O Streptococcus (58) / >,, Cepholothin ' Apici!" n - Aoxc Seru Levels Following The Oral Adinistration Of 500g. Of Apicillin And Aoxicillin lin and considerably ore active than cephalothin against group A beta-heolytic streptococci and pneuococci. Cephalothin was the ost active antibiotic against S. aureus, and inhibited all penicillin G-susceptible and -resistant isolates at a concentration of 0.78 Ag/l or less. Aoxicillin FIG. 5. Mean serui levels following the oral adinistration of 500 g of aoxicillin and 500 g of ainpicillin.
VOL. I1, 197 AMOXICILLIN 361 and apicillin were siilar in activity against Proteus spp. and ore active than cephalothin. Apicillin was slightly ore active than aoxicillin against E. coli and considerably ore active against ebers of the Klebsiella-Enterobacter- Serratia group. Seru levels obtained after oral adinistration of 15 g and 50 g of aoxicillin are shown in Fig. 4. The ean peak seru level after the 15-g dose was achieved at 1 hl and was.30,tg/l. A ean seru level of 0.47,tg/l was present at 4 hr. The ean peak seru level after the 50-g dose occurred between 1 and hr and was 3.43,ug/l. A ean seru level of 1.45 jig/l was present at 4 hr. A coparison was ade between seru levels FIG. 6. 1-B 18 16 14 z 1 0 o t z 0 (-' 8 Un 6 4 achieved after oral adinistration of 500 g of aoxicillin and 500 g of apicillin (Fig. 5). With aoxicillin, the ean peak seru level occurred at hr and was 6.75 jug/l. With apicillin, the ean peak seru level occurred at 3 hr and was.8,ug/l. Between 1 and 3 hr, the differences in the seru levels were statistically significant. Mean seru levels obtained after the oral adinistration of 1 g of aoxicillin with and without probenecid are shown in Fig. 6. The ean peak seru level obtained when the drug was given alone was 9.90 ug/l, and a ean seru level of 1.11,ug/l was still present at 6 hr. When aoxicillin was given with probenecid, the ean peak seru level obtained was 16.04,ug/l. The Seru Levels Following the Oral Adinistration of Gra of Aoxicillin With and Without Probenecid 1. Mean seru levels following the oral adinistration of I g ofaoxkillin with and without probenecid. TABLE 1. - With Probenecid - Without Probenecid Urinary excretion during 6 hr after adinistration of aoxicillin Mean urinary excretion Drug Dose (g) Mean urinary concn (Cg /J) g % Aoxicillin 15 98 (67-11)a 78 48 (137-950) 50 175 (15-50) 70 843 (376-1,359) 500 349 (16-495) 70 1579 (590-,00) 1,000 77 (300-1,000) 73 3313 (880-6,400) Apicillin 500 31 (31-443) 64 1041 (610-1,650) a Nubers in parentheses indicate range of values.
36 BODEY AND NANCE ANTIMICROB. AG. CHEMOTHER. ean seru levels at 8 and 1 hr were 1.30,ug/l and 0.30,ug/l, respectively. The peak seru level in different individuals occurred fro 30 in to 4 hr after drug adinistration. Considering the highest seru level achieved in each subject with the different doses of aoxicillin, the eans were.40,g/l with 15 g, 4.69,ug/l with 50 g, 7.34,ug/l with 500 g, 10.74,ug/l with 1 g, 17.41 Ag/l with 1 g of aoxicillin plus probenecid, and.68 Ag/l with 500 g of apicillin. The urinary excretion of the antibiotics was deterined during the first 6 hr of each study (Table 1). The urinary concentrations varied considerably depending on the aount of urine excreted. The ean proportion of aoxicillin excreted in the urine with each dose varied between 70 and 78%. DISCUSSION Aoxicillin is a new seisynthetic penicillin with an antibacterial spectru siilar to apicillin. The results of our in vitro susceptibility studies are siilar to those of other investigators (7, 10). However, only 60% of our isolates of E. coli wereinhibitedby 1.5 ug or less of aoxicillin per l copared to 80% of isolates in other studies. Most of our patients are exposed to ultiple antibiotics which ay account for this difference. Interestingly, 40% of our isolates of nonpigented S. arcescens were inhibited by 5 jig or less of this drug per l copared, to less than 10% of isolates in other series. Seru levels in this study were lower than those obtained by Croyden and Sutherland, although a siilar assay ethod was used (). Our results agreed ore closely with those of Neu et al. (8), but we obtained lower seru levels with apicillin. Our seru levels of apicillin were siilar to those of Klein et al. (3) in their earlier studies of this drug. All of the studies of aoxicillin have deonstrated that this drug produces substantially higher seru levels than the sae dose of apicillin. Recent studies have suggested that a single oral dose of 3.5 g of apicillin plus probenecid is effective for the treatent of gonorrhea in ales (4). The ean highest seru level of apicillin achieved with this regien was 35.7 jg/l. By substituting 1 g of aoxicillin, we achieved a ean highest seru level of 17.41,ug/l with a ean seru level of 0.30 Ag/l present at 1 hr. It sees probable that equally good clinical results could be achieved with lower doses of aoxicillin. The ajor advantage of aoxicillin over apicillin is that it produces substantially higher seru levels after oral adinistration. Clinical trials are in progress to deterine its effectiveness for the treatent of infections. ACKNOWLEDGMENTS This investigation was supported in part by a Grant-in-Aid fro Beecha-Massengill Pharaceuticals, Division of Beecha, Inc., Clifton, N.J. G.P.B. is a Scholar of The Leukeia Society of Aerica, Inc. LITERATURE CITED 1. Acred, P., P. A. Hunter, L. Mizen, and G. N. Rolinson. 1971. a-aino-p-hydroxybenzylpenicillin (BRL-333), a new broad-spectru seisynthetic penicillin: in vivo evaluation. Antiicrob. Ag. Cheother. 1970, p. 416-4.. Croydon, E. A. P., and R. Sutherland. 1971. a-aino-phydroxybenzylpenicillin (BRL-333), a new seisynthetic penicillin: absorption and excretion in an. Antiicrob. Ag. Cheother. 1970. p. 47-430. 3. Klein, J. O., M. Finland, and C. Wilcox. 1963. Apicillin activity in vitro and absorption and excretion in noral young en. Aer. J. Med. Sci. 45:544-555. 4. Kvale, P. A., T. F. Keys, D. W. Johnson, and K. K. Holes. 1971. Single oral dose apicillin-probenecid treatent of gonorrhea in the ale. J. Aer. Med. Ass. 15:1449-1453. 5. MacLowry, J. D., and H. H. March. 1968. Seiautoatic icrotechnique for serial dilution-antibiotic sensitivity testing in the clinical laboratory. J. Lab. Clin. Med. 7: 685-687. 6. Mantel, N. 1961. Rapid estiation of standard errors o eans for sall saples. Aer. Statistician 5:1-. 7. Neu, H. C., and E. B. Winishell. 1971. In vitro antiicrobial activity of 6[D(-)ca-aino-p-hydroxyphenylacetaido] penicillanic acid, a new seisynthetic penicillin. Antiicrob. Ag. Cheother. 1970, p. 407-410. 8. Neu, H. C., and E. B. Winshell. 1971. Pharacological studies of 6[D( -)ac-aino-p-hydroxyphenylacetaido] penicillanic acid in huans. Antiicrob. Ag. Cheother. 1970, p. 43-46. 9. Sidell, S., R. E. Burdick, J. Brodie, R. J. Bulger, and W. M. M. Kirby. 1963. New antistaphylococcal antibiotics. Arch. Int. Med. 11:1-8. 10. Sutherland, R., and G. N. Rolinson. 1971. a-aino-p-hydroxybenzyl penicillin (BRL-333), a new seisynthetic penicillin: in vitro evaluation. Antiicrob. Ag. Cheother. 1970, p. 411-415.