Elliot S. Vesell

The antipyrine test in clinical pharmacology: Conceptions and misconceptions

Since its introduction 11 years ago,75, 77 the antipyrine test, devised to determine quantitatively the effect of individual environmental factors on hepatic drug‐metabolizing capacity in normal subjects, has been widely used by clinical pharmacologists, as indicated by the large number of applications listed in Table 1. Yet there have been several technical modifications, new extensions and unresolved problems, and an increasing number of apparently conflicting results. This warrants a fresh look at the antipyrine test and a critical reassessment of its applications and limitations.

Genetic control of drug levels in man: antipyrine.

Antipyrine was administered to identical or monozygotic twins and to fraternal or dizygotic twins. Individuals with identical genotypes (monozygotic twins) exhibited significantly less variability in antipyrine halflife than did genetically different individuals (dizygotic twins). Therefore variations in antipyrine metabolism appear to be determined genetically rather than environmentally. In the 36 twins tested, antipyrine half-lives varied between 5.1 and 16.7 hours. No significant correlation occurred between half-lives for phenylbutazone and antipyrine in the 28 twins who received both drugs.

Quantitative Assessment of Hepatic Function by Breath Analysis after Oral Administration of [14C]aminopyrine

The rate of hepatic metabolism of dimethylaminoantipyrine (aminopyrine), which occurs primarily through N-demethylation, was assessed by measurement of the specific activity of 14CO2 excreted in breath samples obtained 2 hours after oral administration of a trace dose of [14C]aminopyrine. The percentage of administered 14C excreted in 14CO2 in 2 hours was 7.0 +/- 1.3 (SD)% in control patients, and significantly less (P less than 0.01) in patients with portal cirrhosis (2.6 +/- 1.2%), fatty liver (4.7 +/- 1.1%), hepatitis (2.6 +/- 1.4%), and hepatic malignancy (3.5 +/- 1.8%). In 16 of 24 subjects with cholestasis not caused by malignant disease the mean 14CO2 excretion was normal. The 14CO2 excretion in patients with portal cirrhosis correlated highly with aminopyrine metabolic clearance rate (r equals 0.92), serum albumin (r equals 0.75), and retention of bromsulphalein (r equals 0.73). Abnormal 14CO2 excretion returned to normal in patients with hepatitis, when the hepatitis resolved. The data suggest that the aminopyrine breath test is a safe, simple, qualitative and quantitative liver function test.

Assessment of Aminopyrine Metabolism in Man by Breath Analysis after Oral Administration of 14C-Aminopyrine

Abstract To determine whether hepatic drug metabolism might be conveniently assessed by a breath analysis technic, 4-dimethyl-14C-amino-antipyrine (aminopyrine) was administered orally to healthy ambulant and nonambulant volunteers and to patients with portal cirrhosis; some of the volunteers were restudied after pretreatment with either phenobarbital or disulfiram. 14CO2 output was estimated semiquantitatively from interval breath samples. Aminopyrine metabolic clearance rate and 12-hour breath 14CO2 output in the healthy volunteers studied before and after drug pretreatment correlated highly(r = 0.91). The metabolic clearance rate was 46 ± 7 ml per minute (mean ± S.E.) in the patients with portal cirrhosis, and 122 ± 20 ml per minute in the healthy controls (p < 0.01). Twelve-hour breath 14CO2 output was 13.8 ± 1.5 per cent in the patients with portal cirrhosis, and 32.6 ± 2.3 per cent in the nonambulant controls (p < 0.01). The data suggest that in vivo breath analysis after administration of 14C-amino...

From Human Genetics and Genomics to Pharmacogenetics and Pharmacogenomics: Past Lessons, Future Directions

This review is dedicated to the memory of our dear friend and colleague Professor Werner Kalow (1916–2008) A brief history of human genetics and genomics is provided, comparing recent progress in those fields with that in pharmacogenetics and pharmacogenomics, which are subsets of genetics and genomics, respectively. Sequencing of the entire human genome, the mapping of common haplotypes of single-nucleotide polymorphisms (SNPs), and cost-effective genotyping technologies leading to genome-wide association (GWA) studies—have combined convincingly in the past several years to demonstrate the requirements needed to separate true associations from the plethora of false positives. While research in human genetics has moved from monogenic to oligogenic to complex diseases, its pharmacogenetics branch has followed, usually a few years behind. The continuous discoveries, even today, of new surprises about our genome cause us to question reviews declaring that “personalized medicine is almost here” or that “individualized drug therapy will soon be a reality.” As summarized herein, numerous reasons exist to show that an “unequivocal genotype” or even an “unequivocal phenotype” is virtually impossible to achieve in current limited-size studies of human populations. This problem (of insufficiently stringent criteria) leads to a decrease in statistical power and, consequently, equivocal interpretation of most genotype-phenotype association studies. It remains unclear whether personalized medicine or individualized drug therapy will ever be achievable by means of DNA testing alone.

Genetic Control of Drug Levels in Man: Phenylbutazone

Phenylbutazone was administered to seven pairs of identical (monozygotic) twins and to seven pairs of fraternal (dizygotic) twins. Individual half-lives ranged from 1.2 to 7.3 days. Subjects with identical genotypes (monozygotic twins) exhibited very similar phenylbutazone half-lives; significantly greater differences in half-life occurred in dizygotic twins. The previously established large variations among individuals in phenylbutazone metabolism appear to be genetically, rather than environmentally, determined.

Localization of Lactic Acid Dehydrogenase Activity in Serum Fractions

Summary 1. Using the method of Wroblewski and LaDue the LDH activity in serum has been localized to 3 electrophoretic regions. In 6 control subjects approximately 48% of the LDH activity in serum was present in the α2-globulin, 33% between the α1-globulin and albumin and 19% in the β-globulin. 2. Three peaks corresponding approximately to those found in serum were observed in the hemolysate from human red cells. In the 2 cases of myocardial infarction in which the total LDH activity was increased the α1 activity peak was differentially raised while in 3 cases of leukemia, although the total activity was increased in only one instance, the percentage of the total LDH activity in the α2 peak was uniformly increased. 3. The results obtained suggest that an examination of the LDH activity in the different serum fractions may provide a more sensitive index of alterations of LDH activity than examination of the total serum concentration of the enzyme. 4. The distinguishing chemical and physical properties of the enzymes in the three peaks, in addition to the observed electrophoretic difference, remain to be studied.

Impairment of Drug Metabolism in Man by Allopurinol and Nortriptyline

Abstract Normal medical students received either allopurinol or nortriptyline. To quantitate changes in rates of drug metabolism produced by allopurinol or nortriptyline administration, the plasma half-lives of antipyrine or bishydroxycoumarin were determined both before and 24 hours after the last dose of allopurinol or nortriptyline. Allopurinol and nortriptyline each markedly prolonged the plasma half-lives of antipyrine and bishydroxycoumarin; large individual variations in prolongation times were observed. In rats, allopurinol and nortriptyline each reduced the activity of hepatic microsomal drug-metabolizing enzymes and slightly lowered the level of cytochrome P-450. These results in rats support the interpretation that in man prolongation of antipyrine and bishydroxycoumarin half-lives after allopurinol or nortriptyline pretreatment is produced by reduced rates of drug biotransformation in liver microsomes. Lowering of the usual dose and close monitoring of blood levels of drugs given simultaneousl...

Pharmacogenomics and “Individualized Drug Therapy”

Since 1965 there have been more than 800 pharmacogenetics/genomics reviews — most suggesting that we are on the verge of offering individualized drug therapy to everyone. However, there are numerous reasons why this approach will be extremely difficult to achieve in the foreseeable future. Drug treatment outcome represents a complex phenotype, encoded by dozens, if not hundreds, of genes, and affected by many environmental factors; therefore, we will almost always see a gradient of response. Phenotyping assays of blood enzyme activities (if feasible) are generally more successful than DNA genotyping for predicting unequivocal outcomes of drug therapy in each and every patient. Phenotyping with probe drugs has generally not succeeded, because of the overlapping substrate specificities not only of drug-metabolizing enzymes but also transporters, receptors, ion channels, transcription factors, and other drug targets; drug-drug interactions, enzyme induction and inhibition, and multiple (enzyme, transporter, second-messenger, signal transduction) pathways also present enormous problems. Genotyping to predict drug disposition, efficacy, toxicity, and clinical outcome has been proposed, but the success of genotyping in individualized drug therapy currently appears unlikely because of the many shortcomings (frequency of DNA variant sites, ethnic differences, admixture) and complexities (plasticity of the genome, multiple mechanisms for determining sizes and locations of haplotype blocks) of this approach.Genomics is an important tool in basic research; yet, it is unrealistic to include genotyping within the realm of tests available to the practicing clinician in the foreseeable future. The same can be said for transcriptomics and proteomics, which also rely on available sources (tumors, biopsies, excreta). The newly emerging fields of metabonomics and phenomics might offer solutions to anticipating and decreasing individual risk for adverse drug reactions in each individual patient; however, tests based on these approaches are not expected to become available to the practicing clinician for at least the next 5–10 years.

Genetic control of dicumarol levels in man

The mean half-life of dicumarol in the plasma of seven sets of identical and seven sets of fraternal twins after a single oral dose of 4 mg/kg was 43.6+/-SD 17.9 hr. Half-lives ranged from 7 to 74 hr in these 28 normal adults not receiving other drugs for 2 wk preceding dicumarol administration. Large differences among unrelated individuals in dicumarol half-life disappeared almost completely in identical twins, but persisted to some extent in most sets of fraternal twins. These results indicate that marked differences among subjects in dicumarol half-life are under genetic rather than environmental control. Reproducibility of values for dicumarol half-life was demonstrated. A direct relationship between the dose and the half-life of dicumarol occurred in unrelated volunteers administered progressively larger doses at 10-day intervals. Dose dependence of the half-life of a drug results in increased variability of half-life and hence in greater risks of toxicity on long-term therapy. Risks of toxicity on the one hand and of failure to anticoagulate adequately on the other can be reduced by determining dicumarol half-life before starting long-term therapy. Half-lives for dicumarol and phenylbutzone tended to be correlated in the 28 twins, but no correlation occurred between dicumarol and antipyrine half-lives.