ANTIacmaiAL AozN9s AND CHEMOTHmAPY, Dec. 1977, p. 7484750 Copyright 0 1977 American Society for Microbiology

Vol. 12, No. 6 Printed in U.S.A.

Methadone: Antimicrobial Activity and Interaction with Antibiotics JOHN N. SHEAGREN, IBRAHIM S. BARSOUM, AND MELODY Y. C. LIN* Department of Medicine, The George Washington University Medical Center, Washington, D.C. 20037 Received for publication 11 March 1977

We studied the effect of methadone, alone and in combination with antimicrobial agents, on two strains each of Staphylococcus aureus, Pseudomonas aeruginosa, and Serratia marcescens isolated from blood streams of parenteral drug abusers with bacterial endocarditis. Methadone has its own antibacterial effect, although at supraphysiological concentrations, and is even synergistic with antimicrobial agents against some organisms. Thus, methadone does not interfere with the antibacterial effects of antibiotics in vitro. Bacterial infections occur frequently in parenteral drug abusers, many of whom are on therapy with methadone either at the time they initially become infected or later during hospitalization. Not only are patients on methadone maintenance apparently more susceptible to infection (1), but methadone has also been shown to interact with antimicrobial agents (2, 3). Thus, we decided to assess the direct effect of methadone, as well as its interaction with antimicrobial agents, against bacteria commonly involved in infections in parenteral drug abusers (5, 6, 8). Two strains each of Staphylococcus aureus, Pseudomonas aeruginosa (supplied by Milagros Reyes, Detroit, Mich.), and Serratia marcescens (supplied by John Mills, San Francisco, Calif.), all isolated from the blood streams of parenteral drug abusers with bacterial endocarditis, were studied. Stock solutions of antibiotics were stored at -70°C and thawed immediately before use. Trypticase soy broth was used for growing the test organisms, and blood agar base plates were used for streaking out organisms. Minimal bactericidal concentrations (MBC) of drugs, alone and in combination, were determined in vitro by a microtiter checkerboard broth dilution method (4). Tests were perforned in a microtiter plate containing 96 wells arranged in 8 horizontal rows of 12 wells each (Cooke Co.). An inoculum of 50 ul of an overnight broth culture of the particular bacterium being tested was adjusted to contain approximately 5 x 106 organisms per ml (colony-forming units per milliliter) and was added to each appropriate well. Plates were examined for evidence of growth the next morning with an autotray viewer (Cooke Co.). The MBC was determined by plating a sample from each well showing no visible turbidity on blood agar base.

The lowest drug concentration in which there was no growth of the test organism after plating and incubation at 37°C for 18 to 24 h was the MBC in micrograms per milliliter. The MBC of each drug alone and in combination, was recorded and plotted as an isobologram on an arithmetic scale (7). Full synergism was considered present if bactericidal activity occurred at a fourfold or greater reduction of the MBC of each drug. Partial synergism was defined as a fourfold or greater reduction in concentration of one drug and only a twofold reduction of the other. Additivity was judged to have occurred if only twofold reductions took place in the concentrations of each drug. If the MBC of either drug was not exceeded, the result was felt to be indifferent. Antagonism would have occurred if the concentration of the MBC of one drug alone was exceeded after addition of any quantity of a second drug. The MBC values of methadone and the several antimicrobial agents alone and in combination are shown in Table 1. The MBC of methadone was 625 ,ug/ml for S. aureus, >1,250 ug/ml for P. aeruginosa, and 1,250 pug/ml for S. marcescens. In no instance was true antagonism demonstrated between any of the antimicrobial agents and methadone. In fact, full synergy was demonstrated between nafcillin and methadone for one of the two strains of S. aureus, and partial synergy was demonstrated against a number of the other isolates (see Table 1). Though not reported in the accompanying table, minimal inhibitory concentrations were always within one tube dilution of the MBC of each drug and combination. Thus, methadone has a distinct antibacterial effect, slightly more so against S. aureus than against the two gram-negative organisms tested. Supraphysiological concentrations, never 748

VOL. 12, 1977

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obtainable clinically in patients on methadone maintenance, were required to show an effect. Because no antagonism was found, it seems unlikely that methadone would interfere with therapy of serious bacterial infections in patients on maintenance programs. Of course, methadone could still adversely effect antibacterial host-defense mechanisms and in vivo studies to explore that possibility are presently underway. Carmelita U. Tuazon offered helpful criticism, and Margaret Mattila provided excellent administrative support for this project. Grant support was under the aegis of the National Institute of Drug Abuse (Public Health Service grant 7RO1-DA-01582). LITERATURE CITED 1. Badden, M. M. 1975. Pathology of the addictive states, p. 189-211. In R. W. Richter (ed.), Medical aspects of drug abuse. Harper and Row, Hagerstown, Md. 2. Grispen, W. H., W. A. Krivoy, D. de Wied, and E. Zimmerman. 1975. Effect of rifampicin on develop-

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ment of tolerance to analgesic actions. Life Sci. 17:247-251. Kreek, M. J., J. W. Garfield, C. L. Gutjahr, and L. M. Gusti. 1976. Rifampin-induced methadone withdrawal. N. Engl. J. Med. 294:1104-1106. MacLowry, J. D., M. J. Jaqua, and S. T. Sclepak. 1970. Detailed methodology and implementation of a semiautomated serial dilution microtechnique for antimicrobial susceptibility testing. Appl. Microbiol. 20:46-53. Mille, J., and D. Denis. 1976. Serratia marcescens endocarditis: a regional illness associated with intravenous drug abuse. Ann. Intern. Med. 84:29-35. Reyes, M. D., W. A. Palutke, R. F. Wylin, and A. M. Lerner. 1973. Pseudomonas endocarditis in the Detroit Medical Center 1969-1972. Medicine 52:173-194. Sabath, L. D., and V. M. Lorian. 1977. In vitro tests for antibacterial activity of antibiotics in combination, p. 131-144. In A Bondi, J. T. Bartola, and J. E. Pier (ed.), The clinical laboratory as an aide in chemotherapy of infectious diseases. University Park Press, Baltimore. Tuazon, C. U., T. A. Cardella, and J. N. Sheagren. 1975. Staphylococcal endocarditis in drug users: clinical and microbiologic aspects. J. Am. Med. Assoc. 135:1555-1561.

Methadone: antimicrobial activity and interaction with antibiotics.

ANTIacmaiAL AozN9s AND CHEMOTHmAPY, Dec. 1977, p. 7484750 Copyright 0 1977 American Society for Microbiology Vol. 12, No. 6 Printed in U.S.A. Methad...
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