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Biomedical subjects

J R Koup

Publications and source records attributed to J R Koup.

At least 19 recordsLinked to original sources
PubMed1979

Stability of pulmonary function during periodic intravenous bolus aminophylline therapy.

Peak expiratory flow, forced vital capacity, forced expiratory volume at 1 sec, and midmaximal expiratory flow were measured immediately before and 1 hr after a scheduled intravenous maintenance dose of aminophylline in 12 recently hospitalized asthmatic patients. Serum theophylline concentrations were also determined. No significant improvement was noted in any of these pulmonary function tests despite a significant increase in serum theophylline concentration (10.5 +/- 5.2 to 18.2 +/- 6.3 micrograms/ml, p < 0.001). These results were consistent with previously developed pharmacologic response theory.

Aminophylline↗
PubMed1979

Chloramphenicol pharmacokinetics in hospitalized patients.

The apparent body clearance of chloramphenicol was investigated in 21 hospitalized adult patients on 27 occasions. Apparent body clearance was found to be significantly lower (1.99 +/- 1.49 ml/min per kg) in patients with total serum bilirubin concentrations of >1.5 mg/100 ml than in patients with serum bilirubin concentrations of </=1.5 mg/100 ml (3.57 +/- 1.72 ml/min per kg; P < 0.001). Serum protein binding of chloramphenicol was lower in cirrhotic patients (42.2 +/- 6.8% bound) than in normal adults (53.1 +/- 5.2% bound; P < 0.001). Low binding of chloramphenicol was also found in the serum of premature neonates (32.4 +/- 8.2% bound; P < 0.001). Reduced binding in neonates implies the need for a lower therapeutic range of total chloramphenicol concentration (3.5 to 13.9 mug/ml) compared with the usual adult range (5 to 20 mug/ml). Finally, three case reports are presented which demonstrate marked abnormalities and intrasubject variation in chloramphenicol clearance.

Adolescent↗
PubMed1979

Relationship between serum and saliva chloramphenicol concentrations.

The relationship between serum and saliva chloramphenicol (CAP) concentrations was evaluated in 27 paired specimens collected from 20 hospitalized patients during therapy with the drug. A significant (R = 0.80, P < 0.001) but variable relationship was found to exist. Serum protein binding of CAP was also evaluated (43.7 +/- 5.7% bound; N = 24). Differences in CAP binding did not apparently account for a significant portion of the variability in the observed saliva/serum CAP concentration ratios. The degree of variation observed indicated that saliva CAP concentrations could not be relied upon for the prediction of serum CAP concentrations.

Adult↗
PubMed1979

Single point clearance estimation.

Linear relationships were observed between the log of total body clearance (C1B) and simulated serum concentrations (Cmin) six hours after a test dose of chloramphenicol, as well as between C1B and the reciprocal of Cmin. Correlation coefficients for these relationships were 0.988 and 0.977, respectively. Clearance estimates obtained from a single serum sample following a test dose of a drug may prove to be a useful method of predicting dosage requirements for individual patients.

Chloramphenicol↗
PubMed1978

Interaction of chloramphenicol with phenytoin and phenobarbital. Case report.

The effect of chloramphenicol therapy (48 mg/kg/day) on the serum concentrations of phenytoin and phenobarbital was studied in a patient previously stabilized on anticonvulsant medications. Phenytoin, 12 mg/kg/day, and phenobarbital, 5 mg/kg/day resulted in serum concentrations averaging 10.8 microgram/ml before and 30.5 microgram/ml, after chloramphenicol therapy. A reduction in dose of both phenytoin and phenobarbital was required to minimize adverse effects during the course of chloramphenicol therapy. An average daily dose of phenytoin of 9.1 mg/kg resulted in an average serum concentration of 17.8 microgram/ml. A daily dose of phenobarbital of 4.0 mg/kg resulted in an average serum concentration of 37.1 microgram/ml. These changes indicate 50.5% and 40.4% decreases in clearance of phenytoin and phenobarbital. Multiple-dose nonlinear regression analysis of phenytoin and phenobarbital serum concentration data obtained during chloramphenicol therapy indicated a 62.5% and a 29.5% decrease in clearance. Subsequent serum concentration monitoring demonstrated a similar reduction in phenobarbital clearance when chloramphenicol was added to phenobarbital alone.

Adult↗
PubMed1978

Ethosuximide pharmacokinetics in a pregnant patient and her newborn.

Ethosuximide concentration in serum was monitored during the last trimester of pregnancy in a patient. After delivery, the decline in serum concentration of ethosuximide was observed in the nonnursing neonate. The half-life of elimination of transplacentally acquired ethosuximide in this neonate was 41.3 hr. The ratio of breast milk to maternal serum concentration of ethosuximide was approximately 1. A total daily exposure to ethosuximide of 12.8 to 38.4 mg (3.6 to 11.0 mg/kg) as a result of nursing was predicted.

Adult↗
PubMed1978

High-performance liquid chromatographic assay of chloramphenicol in serum.

A new method for the analysis of serum chloramphenicol by reversed-phase, high-performance liquid chromatography (HPLC) is described. The method involves a preliminary extraction of 0.1 ml of serum with ethyl acetate containing an internal standard, chromatography with a reversed-phase C18 microparticulate column with an acetonitrile-acetate buffer mobile phase, and detection by measuring UV absorbance at 270 nm. Assay performance was compared with an existing microbiological assay. The HPLC method demonstrated both increased precision and increased sensitivity. The specificity of the HPLC method was also evaluated. The new method presents an alternative approach to the analysis of clinical specimens.

Chloramphenicol↗
PubMed1978

Comparison of homogeneous enzyme immunoassay and high-pressure liquid chromatography for the determination of theophylline concentration in serum.

A comparison of the new homogeneous enzyme-multiplied immunoassay technique (EMIT, Syva) with a high-pressure liquid chromatographic technique for the determination of theophylline concentration is presented. The accuracy, precision, and specificity of the methods were compared. In addition, 100 samples from 61 pediatric patients receiving theophylline were assayed by both methods. The accuracy, precision, and specificity of the enzyme immunoassay support the use of this method for the quantification of theophylline concentration in clinical specimens. A significant correlation (R = 0.981, P less than 0.001) was found between results generated by enzyme immunoassay and high-pressure liquid chromatography for patient samples. The regression line relating these results had an intercept of 0.22 microgram per ml, a slope of 1.05, and a standard error of the estimate of 1.36 microgram per ml.

Caffeine↗
PubMed1978

A useful method for predicting creatinine clearance in children.

A practical method for predicting creatinine clearance for pediatric patients from serum creatinine concentration and patient age is presented. Creatinine excretion rate (ER) can be predicted from the patient's age, in years, by the formula: ER = (0.035 X age) + 0.236. Using the predicted excretion rate and serum creatinine concentration, creatinine clearance can be predicted. There was good correlation (r = 0.90) between predicted and observed creatinine clearances in 101 subjects with various degrees of renal impairment. This method allows renal function to be rapidly estimated.

Adolescent↗
PubMed1977

Paradoxical behavior of serum digoxin concentrations in an anuric neonate.

Serum digoxin values were determined in a newborn infant with severe heart failure and renal failure. The half-life of digoxin in the serum appeared to change, possibly the result of prolonged distribution and/or absorption owing to circulatory insufficiency, or to the accumulation of cross-reacting metabolites of digoxin in the serum. No clinical toxicity was apparent, and no cardiac arrhythmia was observed. The need for monitoring serum digoxin concentration and clinical effect in newborn infants is emphasized.

Anuria↗
PubMed1977

Intravenous theophylline therapy: nomogram guidelines.

We evolved a nomogram for guiding and standardizing intravenous theophylline therapy in hospitalized patients. It provides rapid calculation of a loading dose based on body weight and previous therapy and a maintenance infusion rate related to three categories of expected metabolic activity. The guidelines were prospectively used in the treatment of 72 patients, mainly in a respiratory care unit. The nomogram was successfully used to attain near-steady-state serum concentrations in the therapeutic range of 8 to 20 mg/litre in 72% of patients, with only two patients outside of the range of 5 to 25 mg/litre. These guidelines facilitate initial theophylline dosage in older patients with liver and cardiac disease and provide a rational basis for interpreting serum concentration measurements and adjustment of drug therapy.

Adult↗
PubMed1976

Theophylline pharmacokinetics in premature infants with apnea.

The pharmacokinetics of theophylline were examined in eight low-birth-weight infants (gestation: 26-32 weeks: birth-weight: 887-1,480 gm), who received the drug for treatment of primary apnea. The drug was assayed by high pressure liquid chromatography. The final dosage was 1 to 3 mg/kg/6 hour at 25 to 37 days of age. At the time, theophylline had a prolonged half-life ranging from 13 to 29 hours, a relatively large volume of distribution of 0.65 to 2.86 1/kg, and a small body clearance of 23 to 68 ml/hr/kg. The extremely slow and variable elimination of theophylline must be considered in treatment of apneic infants. The initial dosage regimen suggested is a loading dose of 6 mg/kg and a maintenance dose of 2 mg/kg/ 12 hours, with adjustments made based on monitoring of the serum concentration and on an increased biotransformation capability as maturation occurs.

Apnea↗