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Biomedical subjects

R Menendez

Publications and source records attributed to R Menendez.

29 records · Page 2Linked to original sources
PubMed1986

Comparison of the effects of intravenously administered aminophylline and inhaled isoproterenol on normal airways.

Although beta-agonists and anticholinergics have been well documented to alter the resting tone in normal airways, the effects of aminophylline on normal airway function is controversial. We therefore studied the effects of intravenously administered placebo and aminophylline, inhaled isoproterenol, and intravenously administered aminophylline plus inhaled isoproterenol in 8 nonasthmatic subjects using full and partial flow-volume curves, plethysmography, and respiratory resistance as measured by forced oscillation. Isoproterenol, as has been demonstrated previously, caused improvement in FEV1 FEF50, and the flow of a partial flow-volume curve at 75% of the VC (PFEF75). Intravenously administered aminophylline at therapeutic concentrations (17.0 to 22.4 mg/L) resulted in improvement in FEV1, PFEF75, and the total respiratory resistance. Aminophylline and isoproterenol administered together produced additive effects. Thus, contrary to other studies, intravenously administered aminophylline produced a small but significant effect on normal basal airway tone that was less than that seen after an adrenergic agent but proportionally similar to the effects seen in asthmatic subjects.

Adult↗
PubMed1985

Lack of significant arrhythmogenicity from chronic theophylline and beta-2-adrenergic combination therapy in asthmatic subjects.

We monitored 14 asthmatic subjects (aged 18 to 60 years), with multiple 24-hour electrocardiogram (Holter) recordings, who were taking continuous sustained-release theophylline and beta-2-adrenergic therapy for control of their symptoms. All of the patients were enrolled in an efficacy study for the antiasthmatic drug lodoxamide. No patient demonstrated intrinsic cardiac disease by history or by a standard 12-lead electrocardiogram recording prior to entry into the study. All of the patients were stable at the beginning of the study while on therapeutic theophylline concentrations and inhaled and oral beta-2-adrenergics. Attempts were made to decrease the theophylline dosage by sequentially reducing the dose each week to one-half, one-quarter, and discontinuation. Holter monitoring was repeated at the end of each week of a new dose level. Five patients were able to reduce dosage and eight were able to discontinue theophylline completely. Theophylline therapy was associated with a higher mean heart rate (85.4 vs 79.9 bpm). The combination of theophylline and beta-2-adrenergics therapy was not associated with quantitative or qualitative changes in atrial or ventricular ectopic activity over beta-2-adrenergic therapy alone.

Adolescent↗
PubMed1984

Effects of theophylline on inhaled methacholine and histamine in asthmatic children.

The effects of a therapeutic serum theophylline concentration on inhaled methacholine and histamine were studied in 8 stable, moderately severe asthmatic children 8 to 15 yr of age. Placebo or theophylline in a hydroalcoholic solution was administered in a double-blind fashion, and standard histamine and methacholine challenges were performed following both placebo and theophylline. Serum theophylline concentration averaged 13 mg/L (range 4.0 to 22.1). Theophylline caused a significant increase (p less than 0.01, paired t test) in provocative dose for a 20% drop in FEV1 (PD20 FEV1) for both methacholine (from a mean of 19.1 to 57.5) and histamine (75.9 to 144.5). This effect did not correlate with the small (7.6% increase in FEV1) but significant bronchodilatation produced by theophylline. We conclude that theophylline in doses that achieve serum concentrations in the usual therapeutic range produces significant attenuation of the bronchoconstrictor response to methacholine and histamine challenges in asthmatic children. The mechanism and therapeutic implications of this remain undefined.

Adolescent↗
PubMed1983

Sustained-release theophylline. Pharmacokinetic and therapeutic comparison of two preparations.

The serum theophylline concentration profiles and clinical efficacy of two sustained-release theophylline tablets (Quibron-T/SR and Theo-Dur) were compared in 13 asthmatic children requiring continuous theophylline therapy. Quibron-T/SR and Theo-Dur, administered every 12 hours in the same dose for one week, were evaluated in a multiple-dose randomized crossover study. At the end of each week, serial serum theophylline concentrations were measured and spirometry and body plethysmography were performed. No significant differences between treatments were found in bioavailability, adverse effects, clinical symptom scores, or pulmonary function in spite of the fact that Quibron-T/SR and Theo-Dur produced significantly different serum theophylline concentration profiles as measured by a mean percent of fluctuation in serum theophylline levels of 143 for Quibron-T/SR and 65.7 for Theo-Dur. Over the short term of the study the pharmacokinetic differences did not produce significant differences in clinical efficacy.

Adolescent↗
PubMedDate not supplied

Metaproterenol sulfate for asthmatic children with therapeutic serum theophylline concentrations.

The effects of oral metaproterenol sulfate in asthmatic children maintained chronically on therapeutic doses of theophylline were investigated. Metaproterenol sulfate tablets were compared with placebo in a double-blind, cross-over study with 17 asthmatic children (aged 6-11 years) maintained on a sustained-release preparation of theophylline. Spirometric measurements were made to determine the forced expiratory volume in one second (FEV1), and a forced oscillation technique was used to measure total respiratory conductance (TRC). Differences in the variables from baseline studies following the test drug or placebo were recorded at 0.5, 1, 2, 3, and 4 hours after the test dose. Metaproterenol led to a statistically significant improvement in FEV1 and TRC over placebo with a peak difference at three hours (p less than 0.05). The children with a resting FEV1 below 80% predicted experienced the greatest improvement. No serious side effects from metaproterenol were encountered. The forced oscillation technique provided a reproducible noninvasive means of measuring the bronchodilator response in young children. In the recommended doses, metaproterenol can improve pulmonary function in asthmatic children who have abnormal pulmonary function while being maintained on theophylline.

Asthma↗