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Biomedical subjects

C A Naranjo

Publications and source records attributed to C A Naranjo.

At least 109 records · Page 6Linked to original sources
PubMed1980

Variability in heparin effect on serum drug binding.

Heparinized saline was given to seven men and one woman, aged 21 to 42 yr, after a 14-hr fasting period and 2 hr after breakfast; blood was collected in nonoheparinized tubes. Diazepam (D alpha) and warfarin (W alpha) free fractions were determined in serum by equilibrium dialysis to which radiolabeled drug was added. After 50 U heparin (Harris LO14) intravenously, the maximum effect on D alpha, W alpha, and free fatty acids (FFA) developed in 5 min and lasted 20 to 30 min. D alpha rose and W alpha fell (p < 0.01) at 5 min. Cumulative doses of heparin increased FFAs (F4,16 = 18.29, p < 0.0005). D alpha rises (r = 0.73, p < 0.001) and W alpha falls (r = -0.74, p < 0.001) correlated with changes in FFAs. D alpha rises and W alpha falls were greater postprandially than in the fasted state (p < 0.01). Five subjects were randomly assigned up to 400 U intravenously of each of two different heparin lots (Harris LO14, and Organon LA39.) The FFA rises (reflecting heparin lipolytic activity, F1,32 = 179.62, p < 0.0005), D alpha rises (F1,32 = 34.22, p < 0.0005), and the W alpha falls (F1,32 = 33.20, p < 0.0005) by heparin Harris LO14 were greater than those by heparin Organon LA39. Although small doses of heparin, such as those in heparin locks, can affect drug binding, the extent and variability of the effect depends on the biologic activity of the heparin, and varies with manufacturer and lot, exact time of sampling, and eating.

Adult↗
PubMed1980

Intravenous diazepam and oral ethanol interaction.

The mechanism of the interaction between ethanol and diazepam is not known. Six healthy male subjects (aged 21 to 32 yr) were randomly assigned in a balanced crossover study to each of two treatments, 28 days apart: (1) diazepam 10 mg intravenously over 20 min, preceded by 60 min with ethanol 0.7 gm/kg (diluted to 20% v/v) orally over 15 min and followed for 8 hr by ethanol 0.15 gm/kg/hr to maintain the blood alcohol concentrations between 800 to 1,000 mg/l; (2) diazepam 10 mg intravenously over 20 min. The area under the curve (AUC) for total diazepam increased in all subjects (30.1 +/- 10.7%, mean = SD, p < 0.02) after ethanol. Since AUCfree diazepam also rose in all (mean - 26.5 +/- 17.3%) and AUC of the metabolite N-desmethyldiazepam fell (mean = 50.5 +/- 11.7%, p < 0.01) there had been inhibition of hepatic intrinsic clearance of free drug. The susceptibility of individuals to inhibition of N-desmethylation by ethanol is qualitatively determined by total drug concentrations. Estimation of free diazepam concentration coupled with measurement of metabolite affords a qualitative and quantitative evaluation of the mechanism of this interaction.

Administration, Oral↗
PubMed1980

Diurnal variations in plasma diazepam concentrations associated with reciprocal changes in free fraction.

1 The characteristics and mechanism of fluctuations in diazepam and N-desmethyldiazepam concentrations and diazepam free fraction were studied in six volunteers, who received diazepam (10 mg, i.v. over 20 min) and in five chronic diazepam users. 2 Within a day total diazepam and N-desmethyldiazepam concentrations varied significantly (P less than 0.001) and were lower than predicted between 23.00 and 08.00 h and higher by 09.00 h. In contrast, diazepam free fraction also varied significantly (P less than 0.001) and was highest between 23.00 and 08.00 h and lower by 09.00 h. Coincident increases in total diazepam concentrations (P less than 0.005) and decreases in diazepam free fraction were associated with food intake (P less than 0.05). 3 The coincident diurnal variations in diazepam and N-desmethyldiazepam concentrations and the negative correlation between total diazepam concentration and diazepam free fraction (r = 0.73, P less than 0.001) suggest that the mechanism of the fluctuations is intravascular and tissue redistribution rather than effect on drug biotransformation. 4 These variations may introduce large between and within investigator experimental differences in the determination of kinetic parameters. Free drug concentration varies over the day, and within day variations in clinical effect may be observed.

Adolescent↗
PubMed1980

Differential effects of benzodiazepine disposition by disulfiram and ethanol.

The disposition of chlordiazepoxide, diazepam, oxazepam and lorazepam was studied before and after disulfiram administration to normal subjects and alcoholic patients. Similar studies to determine the effect of ethanol administration on diazepam and oxazepam disposition were also performed. After disulfiram, decreases in the plasma clearance of chlordiazepoxide (54%, p < 0.05; diazepam, 41% p < 0.05) and their active metabolites were observed. Oxazepam and lorazepam have no important active metabolites and the effect of disulfiram on their net disposition was minimal. In normal subjects ethanol (> 800 mg/l maintained for 8 h) increased the AUC free diazepam (26.6 +/- 17.3% mean +/- SD, p < 0.05) and decreased the AUC for N-desmethyldiazepam (50.5 +/- 11.7%, p < 0.05) indicating inhibition of diazepam N-desmethylation. In contrast, there was no significant change in the disposition of oxazepam in four healthy subjects after a single oral dose of ethanol. Thus, disulfiram and ethanol appear not to inhibit the metabolic disposition of oxazepam or lorazepam, benzodiazepine derivatives principally biotransformed by glucuronidation. On pharmacokinetic grounds oxazepam and lorazepam may be the drugs of choice if benzodiazepine therapy is required in chronic alcoholics.

Adult↗
PubMed1980

Sex-related variations in the frequency and characteristics of adverse drug reactions.

Sex-related variations in the clinical effects of drugs may be observed. In an intensive prospective drug surveillance study of 1920 patients hospitalized at the Department of Medicine of the J. J. Aguirre Hospital in Santiago, Chile, the frequency of adverse drug reactions (ADR) was significantly higher in females than in males (p < 0.0005). Women presented more commonly gastrointestinal and cutaneous allergic reactions. In males electrolyte disturbances were more frequent. Drugs inducing ADR were very similar in both sexes. Eighty-three per cent of ADR in males and 93% in females were dose-related effects. Hospitalization was lengthened by a significantly higher proportion of ADR in men than in women. Other ADR's risk fators such as age, number of drugs administered and duration of hospitalization did not account for the differences observed. In males with ADR there was a higher proportion of patients with cirrhosis and renal insufficiency. These findings suggest that sex is a determinant of the frequency and characteristics of ADR.

Adolescent↗
PubMed1979

Furosemide-induced adverse reactions in cirrhosis of the liver.

Furosemide is frequently used for ascites and causes adverse reactions (AR). In an intensive prospective drug monitoring study of 1,920 patients, 172 (8.9%) had cirrhosis of the liver and received furosemide. Mean age was 53 years, and 66.3% were male; and 87% had alcoholic cirrhosis. Eighty-eight (51.2%) had 221 events that by consensus of the monitoring team and attending physicians were either definitely of probably related to furosemide. No AR was fatal but 24% of patients had severe reactions. Almost all reactions were dose-related (96%). The most common were electrolyte disturbances (23.3% of patients) and volume depletion (14%). Furosemide-induced coma occurred in 20 (11.6%) patients and was more frequent in patients with prior hepatic encephalopathy (p less than 0.0005). Higher total doses (p less than 0.001), hyerbilirubinemia (p less than 0.05), prolonged prothrombin time (p less than 0.02), and longer hospital stay (p less than 0.001) were associated with higher frequencies of AR to furosemide. The frequency of hypokalemia did not decrease when potassium chloride or potassium-sparing diuretics were added to furosemide therapy. Frequdncy of AR did not correlate with age, sex, renal impairment, serum albumin, transaminase, or alkaline phosphatase.

Administration, Oral↗
PubMed1979

Chlordiazepoxide and oxazepam disposition in cirrhosis.

When disease impairs clearance of drugs, multiple-dose therapy may result in cumulation. The disposition of chlordiazepoxide (CDX), 50 mg infused intravenously over 10 min, was studied in 14 normal subjects and in 11 patients with biopsy-proven cirrhosis. In the normal subjects, mean (+/- SE) kinetic parameters were: t 1/2 beta, 10.0 (+/- 0.9) hr; Vd, 0.38 (+/- 0.04) l/kg; clearance, 0.54 (+/- 0.13) ml/min/kg. Clearance of total drug correlated inversely with serum albumin concentration in normal subjects (r = -0.63). Values in cirrhotic patients were: t 1/2 beta, 34.9 (+/- 8.7) hr; Vd, 0.34 (+/- 0.024) 1/kg; and clearance, 0.185 (+/- 0.34) ml/min/kg. Desmethylchlordiazepoxide (DMCDX), the major metabolite of CDX, appeared in blood of cirrhotic patients less rapidly than in normal subjects. Severity of liver disease did not indicate the impairment of CDX clearance. In 5 of the same cirrhotic patients, mean t 1/2 beta for oxazepam (7.1 +/- 1.0 hr) was 27% longer than in control subjects (5.6 +/- 0.7 hr); the difference is not significant. On kinetic grounds oxazepam may be preferable to chlordiazepoxide in cirrhotic patients since its elimination kinetics are not greatly altered in cirrhosis.

Adult↗
PubMed1979

Inter- and intrasubject variation in diazepam free fraction.

The extent of intersubject variation in diazepam free fraction was measured in fasting plasma of 74 unrelated subjects. Free fraction differences between subjects were significant and ranged from 0.97% to 1.99%. Diazepam free fraction in 29 males was normally distributed about a mean of 1.25% (range, 1.05% to 1.47%), but the distribution in females was skewed to higher free fractions and 40% had values above the highest in males. Albumin concentration (r = -0.27, p less than 0.002) and age (r = 0.44, p less than 0.001) only accounted for a small part of the variation. Within-pair variances were not greater in 11 dizygotic than in 18 monozygotic twin pairs, indicating a greater contribution of environmental than of genetic factors to diazepam binding. The prehemodialysis free fractions of diazepam in 9 uremic patients ranged from 3.44% to 6.69%, and decreased (p less than 0.005) in 7 after 6 hr of hemodialysis. In 10 subjects determination of intrasubject variation in diazepam free fraction between 14-hr fasting and 2-hr postprandial plasma samples indicated that because subjects differ in their pattern of change in free fraction (p less than 0.001), the overall decrease in mean free fraction did not achieve statistical significance (p = 0.10). The mean relative percent change in free fraction within subjects after feeding was 15.2%.

Adult↗