Summary
In this article, many of the reports which describe the various assay procedures for 8 of the most commonly monitored drugs in plasma (digoxin, gentamicin, phenobarbitone, phenytoin, procainamide, quinidine, salicylates and theophylline) are reviewed, together with studies dealing with interferences of other drugs with these assays. Factors which are evaluated include whether the interference was studied when the drug was taken by a patient or a volunteer or by adding it to serum in vitro, the concentration or dose of the interfering drug (when reported), and the clinical implications of the interference. Suggestions as to how to eliminate some of these potential sources of interference are made.
Similar content being viewed by others
References
Achari, R.G.; Baldridge, J.L.; Koziol, T.R. and Yu, L.: Rapid determination of quinidine in human plasma by high-performance liquid chromatography. Journal of Chromatographie Science 16: 271–273 (1978).
Adams, R.F. and Vandemark, F.L.: Simultaneous high-pressure liquid-chromatographic determination of some anticonvulsants in serum. Clinical Chemistry 22: 25–31 (1976).
Adams, R.F.; Vandemark, F.L. and Schmidt, G.J.: More sensitive high-pressure liquid-chromatographic determination of theophylline in serum. Clinical Chemistry 22: 1903–1906 (1976).
Agdeppa, D.A. and Upton, S.D.: Interference of cephalosporin antibiotics with analysis for theophylline by liquid chromatography. Clinical Chemistry 26: 788–789 (1980).
Ahokas, J.T.; Davies, C. and Ravenscroft, P.J.: Simultaneous analysis of disopyramide and quinidine in plasma by highperformance liquid chromatography. Journal of Chromatography 183: 65–71 (1980).
Al Hakiem, M.H.H.; Nargess, R.D.; Pourfarzaneh, M.; White, G.W.; Smith, D.S. and Hodgkinson, A.J.: Huoroimmunoassay of digoxin in serum. Journal of Clinical Chemistry and Clinical Biochemistry 20: 151–156 (1982).
Anon: Prednisolone; in The bioavailability of Drug Products, pp. 87–90 (American Pharmaceutical Association, Washington D.C. 1978).
Bailey, D.N.: Evaluation of drug interferences in the ultraviolet spectrophotometric analysis of plasma theophylline. Journal of Analytical Toxicology 2: 94–97 (1978).
Banner, A.S.; Berman, E.; Sunderra, E.; Agarmal, M.K.; Kathan, R. and Addington, W.W.: Drug interferences with the spectrophotometric assay of theophylline. New England Journal of Medicine 297: 170–171 (1977).
Boguslaski, R.C. and Denning, CE.: A column radioimmunoassay method for the determination of digoxin. Biochemical Medicine 14: 83–92 (1975).
Boink, A.B.T.J.; Kruyswijk, H.H.; Willebrands, A.F. and Maas, A.H.J.: Some factors affecting a commercial kit for radioimmunoassay of digoxin using tritiated digoxin. Journal of Clinical Chemistry and Clinical Biochemistry 15: 261–266 (1977).
Bond, L.W. and Thornton, D.L.: Trisulfapyrimidine interference with liquid-chromatographic analysis for theophylline and dyphylline. Clinical Chemistry 25: 1186–1187 (1979).
Bowman, D.B.; Aravind, M.K.; Kauffman, R.E. and Miceli, J.N.: Sulfamethoxazole interferes with liquid-chromatographic analysis for theophylline in serum. Clinical Chemistry 26: 1622 (1980).
Brodie, B.B. and Udenfriend, S.: The estimation of quinine in human plasma with a note on the estimation of quinidine. Journal of Pharmacology and Experimental Therapeutics 78: 154–158 (1943).
Burd, J.F.; Wong, R.C; Feeney, J.E.; Carrico, R.J. and Boguslaski, R.C: Homogeneous reactant-labeled fluorescent im-munoassay for therapeutic drugs exemplified by gentamicin determination in human serum. Clinical Chemistry 23:1402–1408 (1977).
Butrimovitz, G.P. and Raisys, V.A.: An improved micromethod for theophylline determination by reversed-phase liquid chromatography. Clinical Chemistry 25: 1461–1464 (1979).
Clark, D.R.: Theophylline assay by liquid chromatography: Removal of acetazolamide interference. Clinical Chemistry 25: 1183 (1979).
Collins, C; Hu, M.; Crowl, C; Kabakoff, D.S. and Singh, P.: A homogeneous enzyme immunoassay for quinidine in serum. Clinical Chemistry 25: 1093 (1979).
Conrad, K.A.; Molk, B.L. and Chidsey, CA.: Pharmacokinetic studies of quinidine in patients with arrhythmias. Circulation 55: 1–7 (1977).
Cook, C.E.; Twine, M.E.; Myers, M.; Amerson, E.; Kepler, J.A. and Taylor, G.F.: Theophylline radioimmunoassay: Synthesis of antigen and characterization of antiserum. Research Communications in Chemical Pathology and Pharmacology 13: 497–505 (1976).
Cornbleet, P.J.; Schmitz, J. and Wolgin, A.: Drugs interfering with theophylline. New England Journal of Medicine 297: 669–670 (1977).
Cramer, G. and Isaksson, B.: Quantitative determination of quinidine in plasma. Scandinavian Journal of Clinical Laboratory Investigation 15: 553–556 (1963).
Crouthamel, W.B.; Kowarski, B. and Narag, P.K.: Specific serum quinidine assay by high-performance liquid chromatography. Clinical Chemistry 23: 2030–2033 (1977).
Daigneault, R.; Cagne, M. and Brazeau, M.: A comparison of two methods of gentamicin assay: An enzymatic procedure and an agar diffusion technique. Journal of Infectious Diseases 130: 642–645 (1974).
Dechtiaruk, W.; Crawford, R. and Frye, R.: Theophylline interference in phénobarbital quantitation. Clinical Chemistry 25: 2055 (1979).
DiPiro, J.T.; Cote, J.R.; DiPiro, C.R. and Bustrack, J.A.: Spironolactone interference with digoxin radioimmunoassay in cirrhotic patients. American Journal of Hospital Pharmacy 37: 1518–1521 (1980).
Drost, R.H.; Plomp, T.A.; Teurissen, A.J.; Maas, A.H.J. and Maes, R.A.A.: A comparative study of the homogeneous enzyme immunoassay (EMIT) and two radioimmunoassays (RIA’s) for digoxin. Clinica Chimica Acta 79: 557–567 (1977).
Dutcher, J.S. and Strong, J.M.: Determination of plasma procainamide and N-acetylprocainamide concentration by highpressure liquid chromatography. Clinical Chemistry 23: 1318–1320 (1977).
Eadie, M.J.: Plasma level monitoring of anticonvulsants. Clinical Pharmacokinetics 1: 52–66 (1976).
Flood, J.G.; Bowers, G.N. and McComb, R.B.: Simultaneous liquid-chromatographic determination of three antiarrhythmic drugs; disopyramide, Hdocaine, and quinidine. Clinical Chemistry 26: 197–200 (1980).
Frings, C.S.; Keefer, R.C. and Saloom, J.M.: A rapid and precise method for determining theophylline in serum. Clinical Toxicology 8: 553–561 (1975).
Frutkoff, I.W.; Kidroni, G. and Menczel, J.: Separation of theophylline from sulfamethoxazole and ampicillin by liquid chromatography. Clinical Chemistry 26: 1765–1766 (1980).
Frutkoff, I.W.; Menczel, J. and Kidroni, G.: Monitoring of serum theophylline by high performance liquid chromatography without interference by various coadministered drugs. Israel Journal of Medical Science 18: 639–641 (1982).
Gannon, R.H. and Phillips, L.R.: Metronidazole interference with procainamide HPLC assay. American Journal of Hospital Pharmacy 39: 1966–1967 (1982).
Giamarellou, H.; Zimelis, V.M.; Matulionis, D.O. and Jackson, G.G.: Assay of aminoglycoside antibiotics in clinical specimens. Journal of Infectious Diseases 132: 399–406 (1975).
Giegel, J.L.; Brotherton, M.M.; Cronin, P.; D’Aquino, M.; Evans, S.; Heller, Z.H.; Knight, W.S.; Krishnan, K. and Sheiman, M.: Radial partition immunoassay. Clinical Chemistry 28: 1894–1898 (1982).
Gupta, R.C. and Lundberg, G.D.: Quantitative determination of theophylline in blood by differential spectrophotometry. Analytical Chemistry 45: 2403–2405 (1973).
Gupta, R.N.; Eng, F. and Stefanec, M.: Estimation of theophylline in plasma by thin-layer chromatography. Clinical Biochemistry 11: 42–45 (1978).
Habbai, Z.M.: Spectrofluorometric assay of gentamicin in serum. Clinica Chimica Acta 95: 301–309 (1979).
Hahn, E.: Dimenhydrinate interferes with radioimmunoassay of theophylline. Clinical Chemistry 26: 1759–1760 (1980).
Harber, M.J. and Asscher, A.W.: A new method for antibiotic assay based on measurement of bacterial adenosine triphosphale using the firefly bioluminescence system. Journal of Antimicrobial Chemotherapy 3: 35–41 (1977).
Huffman, D.H.: The effect of spironolactone and canrcnonc on the digoxin radioimmunoassay. Research Communications in Chemical Pathology and Pharmacology 9: 787–790 (1974).
Jatlow, P.: Ultraviolet spectrophotometry of theophylline in plasma in the presence of barbiturates. Clinical Chemistry 21: 1518–1520 (1975).
Jeffrey, T.M.L.; Benoric, J.L.; Buckler, R.T. and Bard, J.F.: Homogeneous substrate-labeled fluorescent immunoassay for theophylline in serum. Clinical Chemistry 27: 22–26 (1981).
Jeremic’, V.: An improved UV-spectrophotometric method for routine barbiturate monitoring. Journal of Clinical Chemistry and Clinical Biochemistry 14: 479–483 (1976).
Jonkman, J.H.G.; de Zeeuw, R.A. and Schoenmaker, R.: Interference in the proposed selected method for determination of theophylline by liquid chromatography. Clinical Chemistry 28: 1987–1988 (1982).
Jusko, W.J. and Poliszczuk, A.: High-pressure liquid Chromatographic and spectrophotometric assays for theophylline in biological fluids. American Journal of Hospital Pharmacy 33: 1193–1196 (1976).
Kabra, P.M. and Marton, L.J.: Liquid-chromatographic analysis for serum theophylline in less than 70 seconds. Clinical Chemistry 28: 687–689 (1982).
Kawashima, K.; Ishijima, B.; Yoshimizu, N. and Sato, F.: Determination of dose-plasma concentration relationship of phénobarbital in epileptic patients by a new specific radioimmunoassay. Archives Internationales de Pharmacodynamie 244: 166–176 (1980).
Kelly, R.C; Prentice, D.E. and Hearne, G.M.: Cephalosporin antibiotics interfere with the analysis for theophylline by high-performance liquid chromatography. Clinical Chemistry 24: 838–839 (1978).
Krausz, L.M.; Hitz, J.B.; Buckler, R.T. and Burd, J.F.: Substratelabeled fluorescent immunoassay for phénobarbital. Therapeutic Drug Monitoring 2: 261–272 (1980).
Kubasik, N.P.; Brody, B.B. and Barold, S.S.: Problems in measurement of serum digoxin by commercially available radioimmunoassay kits. American Journal of Cardiology 36: 975–977 (1975).
Kumps, A. and Mardens, Y.: A rapid gas-liquid Chromatographic determination of serum levels of phénobarbital and diphen-ylhydantoin. Clinica Chimica Acta 62: 371–376 (1975).
Lam, G.; Huang, S.M.; Lee, M.G.; Nation, R.L. and Chiou, W.L.: Obviating interference with liquid Chromatographie assay of theophylline. Clinical Chemistry 25: 1862–1863 (1979).
Langone, J.J. and Van Vunakis, H.: Immunochemical techniques. Methods in Enzymology 84: 558–577 (1982).
Latham, A.N. and Varlow, G.: Simultaneous quantitative gas-chromatographic analysis of ethosuximide, phenobarbitone, primidone and diphenylhydantoin. British Journal of Clinical Pharmacology 3: 145–150 (1976).
Leslie, J. and Miller, A.K.: Interference in a high pressure liquid Chromatographie assay of theophylline. Therapeutic Drug Monitoring 4: 323–324 (1982).
Lichey, J.; Schroder, R. and Rietbrock, R: The effect of oral spironolactone and intravenous canrenoate-K. on the digoxin radioimmunoassay. International Journal of Clinical Pharmacology 15: 557–559 (1977).
Mahon, W.A.; Ezer, J. and Wilson, T.W.: Radioimmunoassay for measurement of gentamicin in blood. Antimicrobial Agents and Chemotherapy 3: 585–589 (1973).
Manos, J.P. and Jacobs, P.F.: Evaluation of the Bactec serum gentamicin assay. Antimicrobial Agents and Chemotherapy 16: 631–634 (1979).
Marion, A.; Lesko, L.J. and Oliver, G: Procainamide interference with liquid chromatography of theophylline in serum. Therapeutic Drug Monitoring 3: 107–108 (1981).
Mark, L.C.; Kayden, H.J.; Steele, J.M.; Cooper, J.R.; Berlin, I.; Rovenstine, E.A. and Brodie, B.B.: The physiological disposition and cardiac effects of procaine amide. Journal of Pharmacology and Experimental Therapeutics 102: 5–15 (1951).
Matheson, L.E.; Bighley, L. and Hendeles, L.: Drug interference with the Schack and Waxier plasma theophylline assay. American Journal of Hospital Pharmacy 34: 496–499 (1977).
McClean, S.W.; Young, D.S. and Yonekawa, W.: Anticonvulsants in serum, determined with a fully mechanized enzyme analyzer. Clinical Chemistry 23: 116–118 (1977).
McKenzie, S.A.; Edmunds, A.T.; Baillie, E. and Meek, J.H.: Clinical applications of serum theophylline measurement by high pressure liquid chromatography. Archives of Disease in Childhood 53: 322–325 (1978).
Miceli, J.N.; Aravind, M.K.; Cohen, S.N. and Done, A.K.: Simultaneous measurements of acetaminophen and salicylate in plasma by liquid chromatography. Clinical Chemistry 25: 1002–1004 (1979).
Michel, J.; Jacobs, J.Y. and Sacks, T.: Bactericidal effect of combinations of antimicrobial drugs and antineoplastic antibiotics against Gram-negative bacilli. Antimicrobial Agents and Chemotherapy 16: 761–766 (1979).
Miksic, J.R. and Hodes, B.: Theophylline analysis by reversedphase high-pressure liquid chromatography: Elimination of interferences. Journal of Pharmaceutical Sciences 68: 1200–1202 (1979).
Minshew, B.H.; Holmes, R.K. and Baxter, C.R.: Comparison of radioimmunoassay with an enzymatic assay for gentamicin. Antimicrobial Agents and Chemotherapy 7: 107–109 (1975).
Muir, K.T.; Kunitani, M. and Riegelman, S.: Improved high-performance liquid Chromatographie assay for theophylline in plasma and saliva in the presence of caffeine and its metabolites and comparisons with three other assays. Journal of Chromatography 231: 73–82 (1982).
Mulgrave, L. and Rajanayagam, A.: Antagonism in gentamicin bioassay. Medical Journal of Australia 4: 403–404 (1980).
Müller, H.; Brauer, H. and Resch, B.: Cross reactivity of digitoxin and spironolactone in two radioimmunoassays for serum digoxin. Clinical Chemistry 24: 706–709 (1978).
Munro, A.J.; Smith, D.S. and Shaw, E.J.: A simplified quenching fluoroimmunoassay for gentamicin and the effects of some potential interfering factors. Journal of Antimicrobial Chemotherapy 9: 47–51 (1982).
Nelson, J.W.; Cordry, A.L.; Aron, CG. and Barteil, R.A.: Simplified micro-scale procedure for preparing samples for theophylline determination by liquid chromatography. Clinical Chemistry 23: 124–126 (1977).
Nilsson, L.: Factors affecting gentamicin assay. Antimicrobial Agents and Chemotherapy 17: 918–921 (1980).
Oellerich, M.; Külpmann, W.R.; Haeckel, R. and Heyer, R.: Determination of phénobarbital and phenytoin in serum by a mechanized enzyme immunoassay (EMIT) in comparison with a gas-liquid Chromatographie method. Journal of Clinical Chemistry and Clinical Biochemistry 15: 353–358 (1977).
O’Leary, T.D.; Ratcliff, R.M. and Geary, T.D.: Evaluation of an enzyme immunoassay for serum gentamicin. Antimicrobial Agents and Chemotherapy 17: 776–778 (1980).
Osinga, A. and De Wolff, F.A.: Determination of quinidine in human serum in the presence of diuretics. Clinica Chimica Acta 73: 505–512 (1976).
Park, H.M.; Chen, I.W.; Maritasas, G.T.; Lowey, A. and Saenger, E.L.: Clinical evaluation of radioimmunoassay of digoxin. Journal of Nuclear Medicine 14: 531–533 (1973).
Peat, M.A. and Jennison, T.A.: High-performance liquid chromatography of quinidine in plasma with use of a microparticulate silica column. Clinical Chemistry 24: 2166–2168 (1978).
Peng, G.W.; Gadalla, M.A.F. and Chiou, W.L.: High-performance liquid-chromatographic determination of theophylline in plasma. Clinical Chemistry 24: 357–360 (1978).
Peng, G.W.; Gadalla, M.A.F.; Peng, A.; Smith, V. and Chiou, W.L.: High-pressure liquid-chromatographic method for determination of gentamicin in plasma. Clinical Chemistry 23: 1838–1844 (1977).
Phillips, A.P.: The improvement of specificity in radioimmunoassays. Clinica Chimica Acta 44: 333–340 (1973).
Phillips, I. and Shannon, K.: Gentamicin assay in the presence of chloramphenicol. Journal of Antimicrobial Chemotherapy 3: 624–625 (1977).
Powers, J.L. and Sadee, W.: Determination of quinidine by highperformance liquid chromatography. Clinical Chemistry 24: 299–302 (1978).
Pruitt, A.W.; Winkel, J.S. and Dayton, P.G.: Variation in the fate of triamterene. Clinical Pharmacology and Therapeutics 21: 610–619 (1977).
Quattrone, A.J. and Putnam, R.S.: A single liquid-chromatographic procedure for therapeutic monitoring of theophylline, acetaminophen, or ethosuximide. Clinical Chemistry 27: 129–132 (1981).
Ravel, R.: Negligible interference by spironolactone and prednisone in digoxin radioimmunoassay. Clinical Chemistry 21: 1801–1803 (1975).
Reece, P.A. and Peikert, M.: Simple and selective high-performance liquid Chromatographic method for estimating plasma quinidine levels. Journal of Chromatography 181: 207–217 (1980).
Regamey, C; Schaberg, D. and Kirby, W.M.M.: Inhibitory effect of heparin on gentamicin concentrations in blood. Antimicrobial Agents and Chemotherapy 1: 329–332 (1972).
Robinson, C.A. and Dobbs, J.: Acetazolamide interference with theophylline analysis by high-performance liquid chromatography. Clinical Chemistry 24: 2208–2209 (1978).
Robinson, C.A.; Mitchell, B.; Vasiliades, J. and Siegel, A.L.: Cephalosporin antibiotic interference with analysis for theophylline by high-performance liquid chromatography. Clinical Chemistry 24: 1847 (1978).
Rutherford, D.M. and Flanagan, R.J.: Rapid micro-method for the measurement of phenobarbitone, primidone and phenytoin in blood plasma or serum by gas-liquid chromatography. Journal of Chromatography 157: 311–320 (1978).
Schack, J.A. and Waxier, S.H.: An ultraviolet spectrophotometric method for the determination of theophylline and theobromine in blood and tissues. Journal of Pharmacology and Experimental Therapeutics 97: 283–291 (1949).
Scherrmann, J.M. and Bourdon, R.: Cross reactivity of digitoxin in radioimmunoassay and enzyme-linked immunoassay for digoxin in plasma. Clinical Chemistry 26: 670–671 (1980).
Schier, G.M. and Gan, I.E.T.: Interference of theophylline and caffeine in the gas-chromatographic estimation of phénobarbital. Clinical Chemistry 25: 1191 (1979).
Schwertner, H.A.: Analysis for underivatized theophylline by gaschromatography on a silicone stationary phase, SP-2510-DA. Clinical Chemistry 25: 212–214 (1979).
Schwertner, H.A.; Wallace, J.E. and Blum, K.: Improved ultraviolet spectrophotometry of serum theophylline. Clinical Chemistry 24: 360–361 (1978).
Shannon, K..; Warren, C. and Phillips, I.: Interfecence with gentamicin assays by gallium-67. Journal of Antimicrobial Chemotherapy 6: 285 (1980).
Shanson, D.C. and Hince, C.J.: Factors affecting plate assay of gentamicin. HI. Klebsiella assay strains. Journal of Antimicrobial Chemotherapy 3: 563–570 (1977).
Sheehan, M. and Haythorn, P.: Rapid gas Chromatographic determination of underivatized theophylline in whole blood. Journal of Chromatography 117: 393–398 (1976).
Shukur, L.R.; Powers, J.L.; Marques, R.A.; Winter, M.E. and Sadee, W.: Measurement of procainamide and N-acetylprocain-amide in serum by high-performance liquid chromatography. Clinical Chemistry 23: 636–638 (1977).
Silber, B.; Sheiner, L.B.; Powers, J.L.; Winter, M.E. and Sadee, W.: Spironolactone-associated digoxin radioimmunoassay interference. Clinical Chemistry 25: 48–50 (1979).
Sitar, D.S.; Graham, D.N.; Rangno, R.E.; Dusfresne, L.R. and Ogilvie, R.I.: Modified colorimetric method for procainamide in plasma. Clinical Chemistry 22: 379–380 (1976).
Slonek, J.E.; Peng, G.W. and Chiou, W.L.: Rapid and micro high-pressure liquid Chromatographie determination of plasma phenytoin levels. Journal of Pharmaceutical Sciences 67: 1462–1464 (1978).
Soldin, S.J. and Hill, J.G.: A rapid micromethod for measuring theophylline serum by reverse-phase high-performance liquid chromatography. Clinical Biochemistry 10: 74–77 (1977a).
Soldin, S.J. and Hill, J.G.: Routine dual-wavelength analysis of anticonvulsant drugs by high-performance liquid chromatography. Clinical Chemistry 23: 2352–2353 (1977b).
Spiehler, V.; Sun, L.; Miyada, D.S.; Sarandis, S.G.; Walwick, E.R.; Klein, M.W.; Jordan, D.B. and Jessen, B.: Radioimmunoassay, enzyme immunoassay, spectrophotometry, and gas-liquid chromatography compared for determination of phénobarbital and diphenylhydantoin. Clinical Chemistry 22: 749–753 (1976).
Stanley, P.E. and Peikert, M.R.: Determination of phenytoin in plasma: A comparison of procedures using a new radioimmunoassay, gas chromatography, and enzyme immunoassay. Epilepsia 19: 265–272 (1978).
Stearns, F.M.: Determination of procainamide and N-acetylpro-cainamide by high-performance liquid chromatography. Clinical Chemistry 27: 2064–2067 (1981).
Sterling, J.; Cox, S. and Haney, W.G.: Comparison of procainamide analyses in plasma by spectrophotofluorometry, color-imetry and GLC. Journal of Pharmaceutical Sciences 63: 1744–1747 (1974).
Stevenson, G.W.: Rapid ultraviolet spectrophotometric determination of salicylate in blood. Analytical Chemistry 32: 1522–1525 (1960).
Steyn, J.M. and Hundt, H.K.L.: Probenecid, a possible interferent in the gas Chromatographie determination of diphenylhydantoin. Journal of Chromatography 143: 207–209 (1977).
St Onge, L.M.; Dolar, E.; Anglim, M.A. and Least, C.J.: Improved determination of phénobarbital, primidone, and phenytoin by use of a preparative instrument for extraction, followed by gas chromatography. Clinical Chemistry 25: 1373–1376 (1979).
Svensmark, O. and Kristensen, P.: Determination of diphenylhydantoin and phénobarbital in small amounts of serum. Journal of Laboratory and Clinical Medicine 61: 501–507 (1963).
Syva Co.: Procainamide — too much or too little? (Syva Company, Palo Alto, California).
Trinder, P.: Rapid determination of salicylate in biological fluids. Biochemical Journal 57: 301–303 (1954).
Tsay, Y.; Wilson, L. and Keefe, E.: Quantitation of serum gentamicin concentration by a solid-phase immunofluorescence method. Clinical Chemistry 26: 1610–1612 (1980).
Valentine, J.L.; Driscoll, P.; Hamburg, E.L. and Thompson, E.D.: GLC determination of quinidine in human plasma. Journal of Pharmaceutical Sciences 65: 96–98 (1976).
Vandemark, F.L. and Adams, R.F.: Ultramicro gas-chromatographic analysis for anticonvulsants, with use of a nitrogen-selective detector. Clinical Chemistry 22: 1062–1065 (1976).
Vasiliades, J. and Turner, T.: A modified ultraviolet spectro-photometric method for the determination of theophylline in serum in the presence of barbiturates. Clinica Chimica Acta 69: 491–495 (1976).
Walsh, P.R.; Crawford, J.F. and Hawker, CD.: Measurement of digoxin by radioimmunoassay. Annals of Clinical and Laboratory Science 7: 79–87 (1977).
Weidner, N.; Dietzler, D.N.; Ladenson, J.H.; Kessler, G.; Larson, L.; Smith, C.H.; James, T. and McDonald, J.M.: A clinically applicable high-pressure liquid Chromatographic method for measurement of serum theophylline, with detailed evaluation of interferences. American Journal of Clinical Pathology 73: 79–86 (1980).
Weiss, P.; Hersey, R.M.; Dujorne, C.A. and Bianchine, J.R.: The metabolism of amiloride hydrochloride in man. Clinical Pharmacology and Therapeutics 10: 401–406 (1969).
Woodman, T.F.; Canada, A.T. and Seidman, J.: Interference of allopurinol and alloxanthine in ultraviolet theophylline assay. American Journal of Hospital Pharmacy 34: 984–985 (1977).
Zeegers, J.J.W.; Maas, A.H.J.; Willebrands, A.F.; Kruyswijk, H.H. and Jambroes, G.: The radioimmunoassay of plasma digoxin. Clinica Chimica Acta 44: 109–117 (1973).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Yosselson-Superstine, S. Drug Interferences with Plasma Assays in Therapeutic Drug Monitoring. Clin Pharmacokinet 9, 67–87 (1984). https://doi.org/10.2165/00003088-198409010-00004
Published:
Issue Date:
DOI: https://doi.org/10.2165/00003088-198409010-00004