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Biomedical subjects

L M Lopez

Publications and source records attributed to L M Lopez.

At least 73 records · Page 4Linked to original sources
PubMed1986

Effect of concomitant antacid administration on plasma cimetidine concentrations during repetitive dosing.

Previous research has suggested that concurrent administration of antacid and cimetidine results in lower than expected plasma levels of cimetidine. Because these studies were all of single-dose design, this study was undertaken to determine the nature of the interaction after repeated administration of both drugs. There was no statistically significant difference demonstrated for any of the pharmacokinetic parameters evaluated in the study. Based on these findings, the previous recommendation that administration of antacid and cimetidine be separated in time may not be necessary.

Adult↗
PubMed1986

Evaluating the evidence for nutrition interventions: two algorithms.

Community and clinical dietitians are increasingly involved in choosing interventions to alleviate problems and in evaluating programs for their effectiveness. Two decision trees have been developed to assist program planners in this process. The first addresses whether or not a pilot project should be recommended. It deals with determining whether a sufficient problem exists to warrant an intervention, and whether an appropriate intervention that will make a difference can be provided. The second algorithm is directed at the question of whether an existing program should be continued or expanded. It is concerned not only with the outcome of the program but also with its cost-effectiveness.

Decision Making, Organizational↗
PubMed1985

Improvement in exercise performance with nisoldipine, a new second-generation calcium blocker, in stable angina patients.

Safety and efficacy of a new dihydropyridine calcium antagonist, nisoldipine, were studied in 15 patients with proved coronary artery disease and positive exercise treadmill tests. After withdrawal of current therapy and a 2-week placebo phase, patients were given nisoldipine 10, 20, and 40 mg daily (divided into two daily doses), each dose for a 2-week period. Exercise treadmill testing was performed twice during the placebo and once at the end of each nisoldipine phase. Maximal duration of exercise increased with all doses of nisoldipine. Time to 1 mm ST segment depression also increased with all doses of nisoldipine. Peak time to angina was similarly prolonged. Peak exercise double product (heart rate X systolic blood pressure) was unaffected by all doses of nisoldipine. Angina frequency and nitroglycerin consumption decreased during nisoldipine therapy in all patients. Side effects from therapy were only minor. Twice daily therapy compared to three to four times daily therapy with other calcium blockers is an advantage of nisoldipine.

Adult↗
PubMed1985

Comparison of eight phenytoin dosing methods in institutionalized patients.

Until now, no evaluation of phenytoin dosing methods has been undertaken in a large group of patients, to our knowledge. The goal of this study was to determine which of eight different dosing methods most accurately predicts a phenytoin steady-state concentration. Seventy-six patients were chosen, retrospectively, from a state-funded institution for the mentally retarded. Eligibility criteria included two or more different doses of phenytoin and corresponding plasma concentrations. Relative predictive performance was determined by comparing results of simple linear regression. Also, relative bias and precision were determined by comparing mean prediction errors, root mean squared errors, and respective 95% confidence intervals. Of the methods requiring one dose-concentration pair, Rambeck's nomogram was the best predictor of phenytoin concentrations. The methods requiring two known doses and plasma concentrations were more accurate. Their predictive performance was equivalent, although use of the Tozer equation might be preferred for its convenience. None of the methods tested were sufficiently precise to substitute for confirmatory serum phenytoin concentrations.

Adolescent↗
PubMed1985

Computer prediction of serum theophylline concentrations in ambulatory patients.

This study assessed the ability of a computer program Simulated Kinetics (SIMKIN) to predict serum theophylline concentrations in ambulatory patients receiving oral theophylline. Data were collected by retrospective review of prospectively obtained data. A total of only 20 measured serum theophylline concentrations could be included in the study, although records of 195 patients were reviewed. An estimated patient compliance of 90-110% was required and was computed using prescription refill information. Predicted serum theophylline concentrations were generated for each patient by entering into the SIMKIN program the characteristics pertinent to theophylline disposition and the patient's theophylline dosing regimen. Actual and SIMKIN-predicted theophylline concentrations were compared by using simple linear regression and by constructing a 95% confidence interval around the mean prediction error and root mean squared error. The ability of SIMKIN to predict therapeutic category, i.e., subtherapeutic, therapeutic, or toxic, was assessed using Fisher's exact test. SIMKIN predictions of individual theophylline concentration were insufficiently accurate to replace confirmatory followup monitoring of actual levels. However, SIMKIN was able to predict the therapeutic category with 70% accuracy. We conclude that SIMKIN may be useful for categorizing a dose regimen of theophylline as therapeutic, but that it is of little use in predicting individual concentrations in outpatients when literature-averaged pharmacokinetic parameters are the sole criteria for prediction, and compliance cannot be accurately assessed.

Adolescent↗
PubMed1985

Long-term experience with lofexidine in the treatment of mild-to-moderate essential hypertension.

This study describes sustained efficacy and safety of lofexidine in hypertensive patients. Twenty-one male patients (mean age 55 +/- 9 yr) who had previously completed a short-term trial of lofexidine entered this open-label trial. The daily dose of lofexidine was titrated over three months to a maximum of 1.6 mg or an erect diastolic blood pressure less than 90 mm Hg. Hydrochlorothiazide was added when necessary. Thereafter, each patient was evaluated for blood pressure (BP) response, compliance, side effects, hepatic, renal, or hematological abnormalities every three months for two years. Sustained BP reduction with lofexidine was achieved but not without concomitant diuretic therapy. There were no clinically important changes in heart rate or hepatic, renal, or hematological profiles. Side effects were frequent but severe enough to warrant discontinuation in only four patients. The side-effect profile was similar to that of clonidine. We recommend concurrent diuretic use to maximize effectiveness of lofexidine.

Adolescent↗
PubMed1984

Comparative efficacy and safety of lofexidine and clonidine in mild to moderately severe systemic hypertension.

The comparative efficacy and safety of lofexidine and clonidine in patients with mild to moderate systemic hypertension were evaluated. Patients who met established criteria were administered lofexidine or clonidine in a double-blind manner. The dose of either drug, along with hydrochlorothiazide if necessary, was titrated to blood pressure response or to the occurrence of side effects. Treatment with the dose established during titration was continued for 12 weeks. Blood pressure and the occurrence of side effects were evaluated during weekly clinic visits. Twenty-six patients completed all portions of the study. The decrease in blood pressure compared with that with the placebo was significant for both drugs (p less than 0.05). The daily dose of clonidine required for blood pressure control was less than that of lofexidine (p less than 0.05). Concomitant diuretic therapy was required equally as often for both drugs. Clonidine caused adverse effects more frequently than did lofexidine. The effectiveness of lofexidine is comparable to that of clonidine, but lofexidine has a lower incidence of toxicity.

Adolescent↗
PubMed1984

Effect of antacids on predicted steady-state cimetidine concentrations.

The purpose of this study was to evaluate effects of antacids on predicted steady-state concentrations of cimetidine. Ten healthy volunteers received in random order one week apart, cimetidine and cimetidine and antacid suspension. Blood was obtained at specified times and analyzed for cimetidine. Bioavailability was assessed by comparison of peak concentration, time to peak concentration, area under the curve, and time spent over 0.5 micrograms/ml. Single-dose data were extrapolated to steady-state using computer simulation. Concurrent administration of antacid suspension reduced parameters of bioavailability approximately 30%. When steady-state conditions were simulated, concentrations of cimetidine greater than or equal to 0.5 micrograms/ml were maintained for the entire dosing interval in seven of 10 subjects. These data suggest that temporal separation of cimetidine and antacid suspension may be unnecessary.

Adult↗
PubMed1984

Effects of nitrendipine and hydralazine on plasma catecholamines in essential hypertension.

We compared the efficacy and safety of nitrendipine with that of hydralazine in 21 subjects with essential hypertension. Nitrendipine or hydralazine was given in a double-blind manner after a placebo period. Dose was titrated to diastolic blood pressure (BP) less than or equal to 90 mm Hg and the dose established during titration was continued for 5 to 7 wk. Both supine and erect BP were decreased by both drugs, but heart rate was affected only minimally. Myocardial oxygen demand decreased only with nitrendipine (P less than 0.05), although the change may have been the result of somewhat higher systolic BP while on placebo. Hydralazine induced minimal changes in levels of plasma catecholamines, but plasma norepinephrine levels rose in subjects on nitrendipine. Side effects encountered with both drugs were much the same, although nitrendipine was more often associated with mild fatigue. There were mild elevations in liver function parameters in two subjects on nitrendipine. There was little difference between the effects of nitrendipine and hydralazine in hypertension.

Adult↗
PubMed1984

Once-daily propranolol for hypertension.

Twenty patients with essential hypertension, who were receiving a diuretic plus propranolol qid, were instructed to take their entire daily requirement of propranolol as a single morning dose. Blood pressure was measured in standing and supine positions at the end of a dosing interval. Patients were questioned about the occurrence of specific propranolol side effects during each of four bi-weekly evaluations. Mean blood pressure on once-daily propranolol did not differ significantly from that observed on propranolol qid. Daily doses of propranolol ranged from 80-320 mg. Side effects were infrequent and mild. We conclude that propranolol may be administered as a single daily dose to patients with hypertension whose blood pressure already has been controlled on a qid regimen.

Adult↗
PubMed1984

Inadequacy of FDA dosing guidelines for intravenous theophylline.

The ability of a dosing regimen of intravenous theophylline to achieve therapeutic serum theophylline concentrations was evaluated. Intravenous theophylline was administered to 25 adult patients with acute bronchospasm using dosing guidelines 20 percent higher than FDA recommendations. The dose of theophylline was determined by assignment to one of four clinical categories. Blood samples for determination of serum theophylline concentrations were collected 12 and 24 hours after initiation of a constant infusion. Differences between mean observed and target theophylline concentrations did not achieve statistical significance. All patients in categories 1 and 2 achieved therapeutic concentrations of theophylline. Most of those with subtherapeutic levels were smokers suffering from multiple diseases. We conclude that current FDA recommendations for dosing intravenous theophylline are unreliable for routine use in category 3 and 4 patients. Further work is necessary to evaluate these recommendations in pediatric and category 1 and 2 patients.

Adult↗
PubMed1984

Comparison of standard and modified enzyme immunoassay of phenytoin.

A modified method for the enzyme immunoassay (EMIT, Syva Company) of phenytoin is presented and compared with the standard method. Serum samples from 14 patients were analyzed for phenytoin content using both methods. All assays were performed by the same individual. Within-day and between-day variations of the modified method were determined. A carry-over study was done to determine if a sample with a high phenytoin concentration might contaminate subsequent samples with lower concentrations or whether samples with low concentrations could dilute subsequent samples with higher concentrations. Within-day and between-day variations of the modified method were 7.5% and 9.9%, respectively. These values are less than the 10% coefficient of variation limit claimed by the manufacturer of the standard method. The carry-over study revealed no significant carry-over with the modified method. An excellent correlation was observed between the values obtained from the two methods. The modified method can reduce assay costs by up to 40%. The modified method was found to provide accuracy and precision equivalent to the standard EMIT method at a substantial cost savings.

Costs and Cost Analysis↗
PubMed1984

How to establish a pharmacokinetics consulting service for ambulatory patients.

Guidelines on establishing a pharmacokinetics consultation service are presented with emphasis on outpatient services. Need for the service must first be demonstrated, using the literature and local data on frequency of serum drug concentration monitoring for particular drugs and patient subgroups. Physician interest in the program must be determined. The pharmacist intervention may be restricted to technical interpretation of serum drug concentration data, or it can include advice based on the patient's disease process, drug effects, and the interaction between the two. In the service described, a patient interview, a chart review, drug analysis, and a written consultation were provided. A flow chart showing movement of the patient through the service was used, and the pharmacist documented the consultation in the patient's medical record, including recommendations for dosage change and follow-up. Cost items to consider in establishing the service include equipment and supplies, space, and personnel. Staff members who are responsible for serum drug analyses must meet state-specific requirements. In estimating revenues, the current number of requests for serum drug concentrations should be doubled and the institution's estimated rate of collection should be used. After the service is established, the cost of a computerized system for pharmacokinetic predictions may be justified by the increased efficiency of such a system.

Cost-Benefit Analysis↗
PubMed1983

Evaluation of the "condition correction factor" method of estimating theophylline clearance.

The predictive ability of the "condition correction factor" method of estimating total body theophylline clearance as proposed by Powell et al. was evaluated in 22 acutely ill hospitalized patients. Actual theophylline clearance was calculated while the patient was on a constant infusion of aminophylline with serum theophylline concentrations obtained at steady-state conditions. Independently, theophylline clearance was estimated for each patient using condition correction factors. The relationship between actual and estimated total body theophylline clearance was evaluated using multiple regression analysis and correlation testing. The data failed to demonstrate any significant positive correlation between actual and estimated theophylline clearance data. Because of this poor correlation, the use of one of the clearance estimation methods incorporating two serum theophylline concentrations obtained early in therapy is preferable, although less convenient. All estimates of clearance must be considered only as guides for individualization of therapy. Serum concentration monitoring and clinical response of the patient must be considered prior to adjustment of dosage.

Adult↗