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Biomedical subjects

R K Roberts

Publications and source records attributed to R K Roberts.

34 records · Page 2Linked to original sources
PubMed1979

Plasma binding of benzodiazepines in humans.

Plasma binding of chlordiazepoxide, diazepam, loraxepam, and oxazepam was determined by equilibrium dialysis in 20 male, healthy volunteers, 25-86 years old. A wide range of binding was observed, with the free fraction varying twofold for lorazepam, fourfold for chlordiazepoxide and diazepam, and over 20-fold for oxazepam. Statistically significant linear relationships were not observed between the degree of binding and age, serum albumin, or total protein for any of the drugs. There was, however, a correlation between the extent of binding for the four drugs. Because of the importance of unbound benzodiazepine levels in eliciting any pharmacological response and also in disposition, consideration of the wide interindividual variability in plasma binding must be made in interpreting pharmacodynamic and pharmacokinetic data.

Adult↗
PubMed1979

Drug prescribing in hepatobiliary disease.

Liver disease in man is associated with a variety of pathophysiological processes which may influence the disposition of drugs in several ways. Interpretation of the observed pharmacokinetic changes in liver disease requires an understanding of the relationship between systemic drug clearance (Cls), volume of distribution (Vd) and the elimination half-life [t1/2(beta)], i.e. t1/2(beta) = 0.693 . Vd/Cls. Half-life will be a measure of the fluctuation in drug level one may expect with continued administration of a drug while clearance will determine the dose required to achieve a particular steady state level. Liver disease may affect clearance and volume of distribution and so produce changes in half-life; in addition, alterations in plasma binding of drugs may occur and so influence free (unbound) drug levels. It is also possible that the end organ response, particularly in the case of sedative drugs, may be affected by liver disease. Other factors such as age, nutrition, smoking, and concomitant drug therapy may also influence drug elimination in patients with liver disease. At the present time, caution should be exercised in prescribing drugs to patients with liver disease and the dose should be titrated to the clinical response. The development of liver 'function' tests using model or marker drugs may offer some help to the prescriber in the future and enable a less empirical approach.

Adrenal Cortex Hormones↗
PubMed1978

Effect of age and parenchymal liver disease on the disposition and elimination of chlordiazepoxide (librium).

There is an increased incidence of unwanted sedation associated with chlordiazepoxide usage in the elderly and in patients with liver disease. To determine whether pharmacokinetic alterations could account in part for these observations we studied the disposition and elimination of intravenously administered chlordiazepoxide in 27 healthy controls aged 16 to 86 years, 8 patients with cirrhosis, and 5 patients with acute viral hepatitis. Both increasing age and parenchymal liver disease led to similar changes in chlordiazepoxide pharmacokinetics. Over the age range 20 to 80 years, elimination half-life (t1/2(beta)) increased from 7 to 40 hr (r, 0.67; P less than 0.001) attributable to a decrease in plasma clearance from 30 ml per min to 10 ml per min (r, -0.71; P less than 0.001) and an increase in volume of distribution from 0.26 to 0.38 liters per kg (r, 0.60; P less than 0.05). Similarly, a decrease in plasma clearance in cirrhosis (7.7 +/- 2.1 compared to 15.3 +/- 4.4 ml per min, P less than 0.01) and acute viral hepatitis (6.1 +/- 4.3 compared to 18.1 +/- 7.1 ml per min, P less than 0.01) relative to age-matched controls and an increase in the volume of distribution resulted in a prolongation of the elimination half-life in both forms of liver disease. Impaired elimination of chlordiazepoxide may account in part for the increased incidence of oversedation seen in the elderly and in patients with liver disease.

Adolescent↗
PubMed1977

The changing clinical presentation of coeliac disease in adults.

A diagnosis of coeliac disease was confirmed in 57 patients referred to a gastroenterology clinic over a 5 1/2-year period. Although diarrhoea was present in two-thirds of the patients, this was the major symptom leading to referral in less than half of them. When present, diarrhoea was usually intermittent and frequently not typical of steatorrhoea. Symptoms were of less than six months' duration in half the patients, but a review of the past and family history strongly indicated the possibility of coeliac disease in 39 of the 57 patients. A high spontaneous abortion rate during pregnancy was noted. The frequent absence of the classical features of malabsorption, diarrhoea with typical steatorrhoea and chronic debility was noted. All screening tests for malabsorption were found to be unreliable and their routine use was rarely justified. A random serum folate and carotene assay proved as valuable as more expensive and troublesome tests. It is stressed that in any case in which there is a clinical suspicion of this diagnosis, a small intestinal biopsy should be undertaken.

Abortion, Spontaneous↗
PubMed1976

Xylose-1-14C absorption test: the use of urine, serum and breath analysis, and comparison with a colorimetric assay.

The xylose absorption and excretion test has been reassessed in controls and patients with coeliac disease. Xylose has been assayed in both serum and urine colorimetrically and by liquid scintillation counting using xylose-1-14C. The excretion of 14CO2 in breath following administration of xylose-1-14C has been measured. Liquid scintillation counting is a simple and reliable method for the measurement of xylose absorption. Serum xylose levels, urinary xylose excretion, or breath 14CO2 in isolation were poor screening tests for mucosal disease. The use of serum levels and urinary excretion in combination improved the discriminatory value of the test though small gut biopsy was more reliable.

Carbon Dioxide↗
PubMedDate not supplied

Supplemental low flow oxygen prevents hypoxia during endoscopic cholangiopancreatography.

Administration of continuous oxygen during ERCP may prevent hypoxia. Oxygen saturation was recorded using pulse oximetry in 50 consecutive patients undergoing ERCP. Patients were randomly allocated to receive no oxygen or low flow oxygen (2 liters/min) via nasal prongs or nasopharyngeal cannula. Oxygen saturation fell below 90% in 47% of patients not receiving oxygen compared with 0% in those administered oxygen (p less than 0.001). No difference existed in oxygen saturations between those groups receiving supplemental oxygen via nasal prongs or nasopharyngeal cannula. Continuous administration of low flow oxygen is recommended during ERCP.

Aged↗