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Biomedical subjects

R L Yost

Publications and source records attributed to R L Yost.

At least 19 recordsLinked to original sources
PubMed1989

Pharmacokinetics of ranitidine in critically ill infants.

The pharmacokinetic parameters of ranitidine were studied following administration of a single intravenous dose in 9 critically ill infants. Ranitidine disposition was best described by a biphasic elimination curve. For 8 patients, the mean values for T1/2, apparent volume of distribution, and total body clearance were 2.09 h, 1.61 l/kg, and 13.93 ml/min/kg, respectively. Based on simulated steady-state concentration profiles, a dose of 0.7 mg/kg administered intravenously every 6 h should maintain serum levels above 40 ng/ml for 4.7 h of the dosing interval with a wide degree of variability.

Child, Preschool↗
PubMed1987

Cefotaxime stability during in vitro microbiological testing.

Cefotaxime is a broad-spectrum cephalosporin which is metabolized or degraded to less active or inactive metabolites by serum esterases, elevated temperatures, or a pH outside of its stability range. Cefotaxime instability during in vitro microbiological susceptibility tests may lead to an underestimation of the antibacterial activity of the compound. Cefotaxime and desacetylcefotaxime solutions were studied under MIC and serum inhibitory titer testing conditions. Cefotaxime concentrations, as measured by high-performance liquid chromatography, decreased 20 to 30% over the incubation period in various systems tested; the greatest decline occurred in systems containing serum in the media. Changes in the results of microbiological susceptibility tests interpreted after 6 and 18 h of incubation were consistent with changes observed in the high-performance liquid chromatography analysis. This study demonstrates cefotaxime instability under conditions of in vitro microbiological testing.

Cefotaxime↗
PubMed1986

Disposition of cefotaxime and its desacetyl metabolite in morbidly obese male and female subjects.

Cefotaxime sodium (1 g) was injected intravenously in 12 normal (90-110% ideal body weight) and 11 obese (190-210% ideal body weight) male and female subjects. Plasma and urine levels were measured for cefotaxime and its active metabolite desacetylcefotaxime. Kinetic parameters were calculated. Results indicate that a dose adjustment for body weight in obese subjects is not needed, whereas a dose adjustment on the basis of body surface area is reasonable. Metabolite plasma levels in female subjects were significantly higher than in male subjects in both the normal and the obese populations.

Body Surface Area↗
PubMed1985

Rapid chromatographic determination of cefotaxime and its metabolite in biological fluids.

A reversed-phase high-performance liquid chromatographic assay for the simultaneous determination of cefotaxime and its metabolite desacetylcefotaxime in plasma and urine was developed. Plasma was deproteinized with small amounts of acetonitrile. After separation of the proteins the supernatant was extracted with a mixture of chloroform and 1-butanol. A phase separation was obtained leaving the cephalosporin and its metabolite in the aqueous part and extracting most of the interfering endogenous material. The aqueous phase was injected directly into the chromatograph. As part of the plasma water was dissolved in the acetonitrile--1-butanol--chloroform layer, the concentration of the cephalosporin in the aqueous phase was significantly higher than in the original plasma sample. Therefore, the usual diluting effect of the deproteinization could be avoided. In a similar way the assay was applicable to measure cefotaxime and its metabolite in urine. Calibration curves were set up and were linear up to 25 micrograms/ml for desacetylcefotaxime and 250 micrograms/ml for cefotaxime. The assay was applied to study the pharmacokinetics of cefotaxime and its metabolite in a healthy volunteer. In a similar way this deproteinization and extraction method was also applied to assay for ceftazidime, cephalexin, cephazolin and cefoxitin.

Adult↗
PubMed1985

Diurnal variation of alpha 1-acid glycoprotein concentration in normal volunteers.

The serum concentration of alpha 1-acid glycoprotein (AAG) was determined hourly for 25 h in male and female volunteers. Subjects were carefully selected to control for age, weight, health status, smoking history, medication use, and, for females, estrus cycle and oral contraceptive use. Studies were performed under conditions closely controlled for sleep, daytime environment, and diet. All mean concentrations were within the range reported as normal, but the deviation around individual means varied from 6.4 to 48.9%. Males had higher mean AAG concentrations than females, 59.9 versus 52.4 mg/dL, but the difference was not statistically significant. Studies which compare changes in AAG concentration or the degree of basic drug protein binding over time within individuals or between groups should consider intrasubject variability in AAG for accurate interpretation of results.

Adult↗
PubMed1985

Obesity and post-operative pain.

Patients underwent elective abdominal surgery for morbid obesity (mean = 154 kgs, n = 55) or cholecystectomy (mean = 71 kgs, n = 54). Post-operative narcotics were transformed into morphine equivalent units (ME). Morbidly obese patients received significantly fewer total doses than cholecystectomy patients and less total mg ME/kg over a five-day period. Sedative use for both groups was comparable. In the morbidly obese patients, preoperative psychiatric and drug usage data predicted 67% of the variance in number of doses and 69% of the variance in total mg ME/kg.

Adult↗
PubMed1985

Effect of a lactobacillus preparation on the absorption of oral ampicillin.

Lactobacillus preparations have been demonstrated to be beneficial in the prevention of antibiotic-associated diarrhea resulting from ampicillin. Since the bioavailability of oral ampicillin is known to be affected by food and fluid volume, a study to evaluate the influence of a lactobacillus product on ampicillin bioavailability was performed. Twelve healthy volunteers, male and female, were studied in a randomized three-way cross-over study. Each received ampicillin alone, ampicillin with a lactobacillus preparation, and ampicillin followed 1 h later by the lactobacillus preparation. Blood was sampled over a 6-h time period. Ampicillin content was determined by high-pressure liquid chromatography. Area under the concentration-time curve, area under the first moment of the concentration-time curve, maximum concentration of drug in plasma, time to maximum concentration of drug in plasma, and mean residence time were determined for each study interval. No differences in maximum concentration of drug in plasma, time to maximum concentration of drug in plasma, area under the concentration-time curve, or mean residence time were seen for either males or females or the combined group. The lactobacillus preparation as used in this study did not appear to interfere with the bioavailability of oral ampicillin.

Administration, Oral↗
PubMed1983

Evaluation of hypertensive therapy in a skilled nursing facility.

Treatment of hypertension in the elderly has recently received increased attention. Both systolic and systolic plus diastolic hypertension are risk factors for cardiovascular and cerebrovascular diseases in patients older than age 65, but the value of antihypertensive therapy in reducing morbidity and mortality has not been adequately studied. The authors evaluated the appropriateness of antihypertensive therapy prescribed for elderly patients in a skilled nursing home and determined the effect reductions in antihypertensive therapy had upon the function and mental status of these patients. Of the 120 patients surveyed, 26.7 percent were found to have a diagnosis of hypertension, and 1/3 of these patients were not receiving any medications at the time of the study. Assessment of the remaining treated patients resulted in a recommendation to alter therapy in 43 percent of the cases. Results from this study suggest that periodic assessment of antihypertensive therapy in long-term care facilities should be considered.

Aged↗
PubMed1982

Investigation of a dosage regimen for intravenous theophylline.

A study was designed to evaluate the validity of the dosage guidelines for theophylline recommended by Hendeles and Weinberger. A total of seven asthmatic smokers and non-smokers were entered and studied. Theophylline serum concentrations were determined prior to the start of therapy and at intervals following initiation of an infusion. The mean theophylline concentration attained for all subjects was 10 micrograms/ml, however, five of the six patients completing the study did not achieve the predicted serum theophylline concentration. Further study of higher dosage designed to achieve a concentration of 12 micrograms/ml is suggested.

Adult↗
PubMed1981

Selected physiologic and drug effects on serum uric acid levels in an elderly population.

A total of 2,923 elderly subjects were studied to determine the relationship between obesity, hypertension, thyroid disease, renal function, alcohol consumption, selected drugs, and the serum uric acid level. Comparison of the serum uric acid levels with indices of obesity demonstrated a strong correlation in normotensive (p less than .0001) and hypertensive (p less than .001) subjects. The serum creatinine level, when used alone, was not a reliable indicator of renal function. Of the drugs evaluated, diuretics had the most pronounced effect upon the serum uric acid level.

Aged↗
PubMed1981

Practicality of a lithium dosing guide.

A method of dosing lithium based on a 24-hour serum lithium level obtained after a single 600-mg oral dose of lithium carbonate has been reported to provide a steady-state lithium concentration of 0.6--1.2 mEq/liter. Since this regimen is widely used in clinical practice, the authors designed a study to determine the practicality of the dosing guide. Of 13 patients who followed this dosing protocol, 4 (30.7%) failed to achieve the defined steady-state range. The authors discuss factors that may affect the reliability of the dosing guide.

Administration, Oral↗
PubMed1981

Rapid infusion of phenytoin sodium loading doses.

The use of rapid intravenous infusions of phenytoin sodium to achieve prompt plasma therapeutic concentrations of phenytoin was studied in adult epileptic patients. Six adult patients who experienced recent tonic-clonic seizures were selected for study. Four of them had not been treated with phenytoin before the study; two were on chronic phenytoin therapy but had subtherapeutic serum levels. A leading dose of phenytoin sodium (15 mg/kg in 100 ml of 0.9% sodium chloride injection) was infused at 30-50 mg/min. Blood samples were drawn before phenytoin administration, every five minutes during the infusion, and at 1, 2, 4, 8, 12, 18, and 24 hours after completion of the infusion. Adverse effects were monitored during the infusion. Pharmacokinetic variables were calculated. Patients received from 750 to 1500 mg phenytoin sodium (mean +/- S.D. = 1040.8 +/- 297.3 mg). From 5 to 30 minutes were required to reach therapeutic (10-20 micrograms/ml) serum phenytoin concentrations; concentrations peaked at 31.1 +/- 10.0 micrograms/ml. Four of the six patients had therapeutic serum concentrations at 18 hours after completion of the infusion. Adverse effects were minimal and not severe; no cardiotoxicities were noted. Phenytoin half-life was 31.2 +/- 8.4 hours, total plasma clearance was 47.2 +/- 10.7 ml/kg/hr, and volume of distribution was 1.96 +/- 0.46 liters/kg. It is concluded that rapid intravenous infusion of phenytoin appears to be a reasonably safe and effective method of rapidly reaching therapeutic phenytoin concentrations.

Blood Pressure↗
PubMed1980

Evaluation of an educational program on compliance with medication regimens in pediatric patients with renal transplants.

An educational program was initiated in an attempt to improve compliance in taking medications among pediatric renal transplant patients. Compliance was assessed by pill counts and by knowledge about medications by interview and questionnaire before, during, and after a six-month study period. Forty-three percent of the population was initially found to be in some way noncompliant with medication regimens, and 19% remained so after extensive counseling and instruction. Factors associated with noncompliance were adolescence, female sex, and family instability. Compliance was associated with direct parental involvement and voluntary maintenance of medication calendars. Although knowledge about drugs significantly improved, there was no correlation with compliance; motivational factors appeared to be of greater importance.

Adolescent↗
PubMed1979

Doxycycline in the prevention of hepatic dysfunction: an evaluation of its use following jejunoileal bypass in humans.

A prospective randomized study was carried out to evaluate doxycycline hyclate in the prevention of hepatic dysfunction following jejunoileal bypass for morbid obesity. Forty-five patients were entered into the study and were observed for a year or more. Patients received either 100 mg of doxycycline hyclate twice daily on postoperative days 5 through 10 and then 100 mg daily for six weeks, or no drug. At six weeks, 12 weeks, and 12 months after the operation, biochemical levels were measured. After one year all patients had a liver biopsy. Doxycycline, in the regimen, was not demonstrated to be of value in the prevention of hepatic dysfunction in these patients. A lack of correlation was demonstrated between the biochemical definition of hepatic dysfunction and liver histopathology.

Adolescent↗
PubMed1979

Epidemiology of hyperuricemia in an ambulatory elderly population.

The relationship of serum uric acid concentration to age and sex was assessed in 1,701 participants in a geriatric multiphasic screening clinic. Included were 1,067 women and 634 men. The mean uric acid level for men was 6.35 mg/100 ml compared to 5.44 mg/100 ml for women. No statistically significant increases in serum uric acid between age groups were apparent, except for women over 84 years of age. The mean serum urate concentrations found in this geriatric study are higher than those reported for other population groups, suggesting a higher normal value for the elderly.

Age Factors↗
PubMed1979

ASHP Midyear Clinical Meeting papers: 1967--1978.

Trends in the types of topics of papers presented at the American Society of Hospital Pharmacists' Midyear Clinical Meetings from 1967 to 1978 are reviewed. A total of 1,210 abstracts of papers presented at the 12 meetings were reviewed. Twenty-three subject categories were identified. Papers were subdivided into four different study types--review, case report, report, and study. Topics such as general hospital pharmacy, management and administration, and drug distribution were emphasized more during the early years of the meeting. Papers on role evaluation, adverse drug reactions and drug use review were presented more frequently in the early 1970s. Therapeutics and general clinical pharmacy were topics consistently emphasized. Case reports increased from 0% in 1967, to 2% in 1972, to 6% in 1978. Review papers decreased from 72% in 1967, to 11% in 1972, to 3% in 1978. Studies increased from 4% in 1967, to 28% in 1972, to 43% in 1978. Concentration on increasing the number of studies presented at the meeting will advance hospital pharmacy and thus improve patient care.

Congresses as Topic↗