David A. Price Evans

Steady-state plasma levels of nortriptyline in twins: Influence of genetic factors and drug therapy

Nineteen identical (monozygotic) and 20 fraternal (dizygotic) sets of twins between 45 and 51 years of age were given nortriptyline orally in doses of 0·2 mg./kg. body weight three times daily for eight days. The steady-state plasma concentrations of nortriptyline were calculated from the mean of the determinations for days 6, 7, and 8. Identical twins, not treated with other drugs, achieved similar steady-state plasma concentrations of nortriptyline in contrast to fraternal twins who were not given other drugs. The intrapair similarity in steady-state plasma concentrations was not found in identical twins simultaneously treated with various drugs during the experiment. Identical and fraternal twins treated with drugs containing barbiturates had considerably lower steady-state plasma concentrations of nortriptyline compared with untreated twins. It is concluded that most of the variability in nor-triptyline steady-state plasma concentration between persons who have not received drugs is genetically determined. Exposure to other drugs also influences the steady-state plasma concentration of nortriptyline, which in a given patient may therefore be determined by a resultant of genetic and environmental factors.

Frequent occurrence of Cyp2d6 gene duplication in Saudi Arabians

The polymorphic cytochrome P450 2D6 (CYP2D6) causing poor, extensive or ultrarapid metabolism of several clinically important drugs exhibits pronounced interethnic variation. Ultrarapid metabolism is caused by multiple copies of active CYP2D6 genes and recently 29% of an Ethiopian population has been shown to carry duplicated or multiduplicated CYP2D6 genes, whereas the corresponding frequency in other black, Oriental and European populations investigated is 1-2%. In order to characterize the distribution of alleles with multiple CYP2D6 copies in a neighbouring population and to characterize the CYP2D locus in general among Saudi Arabians, the CYP2D6 genotype of a Saudi Arabian population was examined using restriction fragment length polymorphism (RFLP) analysis and allele-specific polymerase chain reaction (PCR) amplification. Of 101 Saudi Arabians studied, 21 subjects had an EcoRI fragment indicative of CYP2D6 gene duplication. In contrast, only two individuals were heterozygous for a deletion of the whole gene (CYP2D6*5). The allele frequency of CYP2D6*4, the most common defective allele among Caucasians, was only 3.5% in the Saudi population. Two other alleles, CYP2D6*10 and *17, common in certain populations and which cause diminished enzyme activity, were found only at low allele frequencies of 3.0% each. These findings are in agreement with earlier Saudi Arabian phenotyping studies which reported a low frequency (1-2%) of poor metabolizers for CYP2D6 probe drugs. In conclusion, the Saudi Arabian population studied exhibited very few defective alleles and a large number of subjects carried duplicated CYP2D6 genes, implying a high conservation on functional CYP2D6 genes possibly due to dietary reasons and reveal the Saudi Arabians as an unique population in comparison with others examined.

Fluconazole improves survival in septic shock: a randomized double-blind prospective study.

ObjectiveTo demonstrate whether fluconazole reduces multiple organ failure and mortality in early septic shock (<24 hrs). DesignA prospective randomized double-blind study. SettingA medical and surgical adult intensive care unit in a tertiary referral center. PatientsValues were obtained from 71 general adult intensive care unit patients. InterventionsDuring a 2.5-yr period, December 1998–June 2001, 71 patients with septic shock attributed to either nosocomial pneumonia (n = 37) or intra-abdominal sepsis (n = 34) were admitted to our intensive care unit and met the criteria of early septic shock and were entered into this study. All patients were randomized by our clinical pharmacist to receive daily either 200 mg of fluconazole in isotonic saline (fluconazole group = 32) or isotonic saline alone (placebo group = 39) intravenously during the course of their septic shock. Measurements and Main ResultsAll patients were closely monitored with pulmonary artery catheters and parameters to calculate daily organ dysfunction and Acute Physiology and Chronic Health Evaluation II scores. There was a highly significant increase in 30-day survival in the fluconazole-treated patients compared with the placebo patients (78% vs. 46%). However, fluconazole was found to be more effective in patients with septic shock attributed to intra-abdominal sepsis than to nosocomial pneumonia. Increased survival in the intra-abdominal sepsis clinical category was mirrored by a significantly lower number of organ failures in the treated group compared with the placebo group whereas the number of organ failures in the fluconazole group attributed to nosocomial pneumonia were not significantly increased compared with the control group. The septic shock state was considered in all cases to be attributed to bacterial and not to disseminated yeast infection with the exception of one patient in the control group who was admitted with candidemia. The mechanisms by which fluconazole exerts its protective effect against septic shock in patients is far from clear. However, fluconazole has been shown to enhance bactericidal activity of neutrophils and also to inhibit transmigration and adhesion of neutrophils in capillaries of distant organs. ConclusionsThe development of organ failure and mortality in septic shock was significantly reduced by fluconazole given intravenously. The mechanism of action of fluconazole in reducing multiple organ dysfunction in this group of patients may be attributed to the ability of fluconazole to increase recruitment, improve bactericidal activity of neutrophils, and to contain microorganisms locally.

Ethnic variation in the HER-2 codon 655 genetic polymorphism previously associated with breast cancer

AbstractHER-2, a protooncogene located on chromosome 17q21, encodes a transmembrane glycoprotein (p185) with tyrosine kinase activity. Alterations of the HER-2 gene have been implicated in the carcinogenesis and prognosis of breast cancer and other solid tumors. It is also a cancer-therapeutic target for antibody-based therapy against the HER-2 protein. A single-nucleotide polymorphism (SNP) at codon 655, resulting in a G-to-A transition (Ile655Val) in the transmembrane domain-coding region of this gene has been associated with an increased risk of breast cancer, particularly among younger women. To understand the importance of this finding throughout the world, we evaluated this polymorphism in Ghanaian, Kenyan, Sudanese, Caucasian, African-American, Saudi, and Filipino subjects using a polymerase chain reaction-restriction fragment length polymorphism assay. The frequency of the Val allele, which is associated with increased breast cancer risk, was highly variable between populations (0%–24%). Continental African populations had a lower frequency of the Val allele than did Saudi, Chinese, Filipino, Caucasian, and African-American subjects. The data suggest that this SNP has variable frequency in different ethnic groups. The findings in this study correspond with the lower incidence and lower risk of breast cancer in African women compared with Caucasian and African-American women.

Evaluation of Spontaneous Reports of Adverse Reactions to Drugs

An adverse drug-reaction monitoring system based on spontaneous reporting to a central register of adverse reactions has been in operation for eight years. As a test of the validity of the reports and of the probability of causal relationship between drug and reaction a random sample of 82 cases were followed up in detail. The sample included 17 deaths, 26 serious reactions, and 39 reactions of moderate or only minor severity. Altogether 78% of the reactions were considered to be “probably” drug related and 13% “possibly” drug related. It is concluded that the reports are of value in the detection and evaluation of drug safety.