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Biomedical subjects

L Hendeles

Publications and source records attributed to L Hendeles.

At least 127 records · Page 7Linked to original sources
PubMed1979

Suppression of seasonal allergic rhinitis symptoms with daily hydroxyzine.

The effectiveness of hydroxyzine in the suppression of allergic rhinitis symptoms was evaluated using a double-blind, parallel study design during the 1977 ragweed season. Forty-three subjects with positive ragweed skin tests and a history of an exacerbation of symptoms during August and September of the previous two years were randomly assigned to receive either hydroxyzine or placebo. Subjects scored the severity and duration of symptoms in a daily diary and adverse effects were evaluated from a structured interview at two-week intervals. Although drowsiness and dry mouth were frequent initially among the hydroxyzine-treated patients, these minor side effects rapidly disappeared as the dose was slowly increased, and all but one subject tolerated 150 mg/day. Subsequently, during the period of the highest ragweek pollen counts, the hydroxyzine-treated group spent significantly more days free of symptoms or with only mild sneezing, rhinorrhea, and eye symptoms than subjects who took placebo (p less than 0.05). Thus, hydroxyzine appeared to be well tolerated on a continuous daily basis and was effective in suppressing most of the symptoms of seasonal allergic rhinitis. Comparison of hydroxyzine with antihistamines more traditionally used for allergic rhinitis appears warranted.

Adult↗
PubMed1978

The relation of product formulation to absorption of oral theophylline.

To assess the potential for therapeutic problems related to the bioavailability of oral theophylline preparations, we examined the rate and extent of absorption for various formulations in adult volunteers. Absorption of theophylline from a solution or from uncoated tablets was rapid and complete. Three of six sustained-release formulations were more slowly, but still completely and consistently, absorbed. Absorption of the other three sustained-release formulations appeared to be more erratic and less complete. Serum concentration-time curves during multiple eight-hour dosing were simulated for the bioavailable preparations. With three sustained-release formulations it was predicted that fluctuations in serum theophylline concentrations between doses would decrease, as compared with uncoated tablets, to a clinically important extent, particularly in children, in whom elimination of theophylline is generally rapid.

Administration, Oral↗
PubMed1978

Oral theophylline dosage for the management of chronic asthma.

Theophylline dosage requirements to maintain serum concentrations of 10 to 20 microgram/ml among asthmatic patients were examined in 156 children, ages 2 1/2 months to 16 years, and 33 otherwise health adults. Using 100% bioavailable preparations, low doses were used initially and increased, if tolerated, at three-day intervals. Final dosage was based on serum theophylline measurements which were subsequently repeated after six or more months of therapy. Dosage standardized by weight averaged 24.1 +/- 5.5 mg/kg/day (mean +/- SD) among the 77 children under age 9 years. Age-related variability of weight-adjusted doses were not observed for younger children, but average dose requirements decreased progressively beyound age 9 years to 13 mg/kg/day for patients beyoung 16 years of age. Although interpatient variability in dosage was confirmed at all ages, intrapatient variability in requirements over an average eight-month interval were small; dosage changes to maintain therapeutic serum concentration were primarily associated with growth. These data allow age-specific guidelines for dosage recommendations based on the likelihood of optimally effective and potentially toxic serum theophylline concentrations.

Administration, Oral↗
PubMed1978

Guide to oral theophylline therapy for the treatment of chronic asthma.

Theophylline, when used appropriately, seems to be the most effective noncorticosteroid prophylactic medication for chronic asthma. Dosage, however, requires consideration of the relationship between serum concentration, efficacy, and toxicity, in addition to the variability in rates of elimination. Therapy is initiated with 16 mg/kg/day or 400 mg/day (whichever is less) in divided doses at appropriate intervals depending on the rate of absorption of the product used. If side effects are absent, the dosage is increased at three-day intervals until the age-related mean dosage necessary to produce a therapeutic level, is reached. Final dosage adjustment is generally based on a single determination of serum concentration; dosage requirements generally then remain constant for six to 12 months depending upon the child's growth rate. Dosage adjustment in this manner optimizes benefit, minimizes risk of toxic effect, and avoids excessive numbers of serum theophylline measurements.

Administration, Oral↗
PubMed1977

Unpredictability of theophylline saliva measurements in chronic obstructive pulmonary disease.

The use of saliva as an indirect, non-invasive method of theophylline plasma level measurement was evaluated in 23 older men with chronic obstructive pulmonary disease and numerous concurrent medical problems. Simultaneously collected plasma and saliva samples were obtained on two or more occasions and analyzed for theophylline concentration by the Schack and Waxler spectrophotometric method. The mean (+/- SD) plasma:saliva ratio for 84 sample sets was 1.6 (+/- 0.5) with the saliva concentration averaging 64.8% (+/- 20.8%) of the plasma concentration. Multiplying a randomly chosen plasma:saliva ratio from each patient by the saliva concentration of a second randomly selected observation resulted in a predicted plasma concentration that differed by more than 20% of the measured concentrations for 16 of the 23 patients. Thus, use of saliva theophylline measurements obtained by the Schack and Waxler method to adjust dosage regimens cannot be recommended in these patients.

Chronic Disease↗
PubMed1977

Management of asthma. 1. Approach.

Management of asthma requires confirmation of the diagnosis; characterization of the severity, chronicity, and precipitating factors; and development of an appropriate treatment plan based on the established efficacy of the various pharmacologic and nonpharmacologic modes of therapy.

Adrenal Cortex Hormones↗
PubMed1977

Management of asthma. 2. Antiasthmatic drugs.

Asthma is a complex disease characterized by hyperreactive airways, with a wide spectrum of severity and presentation. Management requires confirmation of the diagnosis; characterization of the severity, chronicity, and precipitating factors; and development of an appropriate treatment plan based on the established efficacy of the various pharmacologic and nonpharmacologic modes of therapy. For acute symptoms, treatment with sympathomimetic amines appears to be the most appropriate initial measure. Corticosteroids are the most potent drugs available for dealing with acute symptoms that are unresponsive to bronchodilators. For the control of chronic asthma, either theophylline or cromolyn can be used initially. Chronic therapy may also require corticosteroids, in which case toxic effects of long-term therapy can be minimized by use of alternate-day dosage of prednisone or daily inhalation of beclomethasone dipropionate. Concurrent with drug therapy, environmental control measures can be used to minimize exposure to avoidable precipitants, and injection therapy with allergenic extracts can be considered if inhalant allergy can be convincingly demonstrated to play a major role. Failure of airway obstruction to respond to corticosteroids and the other measures should raise serious questions regarding the diagnosis.

Adrenal Cortex Hormones↗
PubMed1977

Drug interference with the Schack and Waxler plasma theophylline assay.

Drug-induced modification of the spectrophotometric theophylline plasma measurement was investigated in vitro using 14 drugs which coextract with theophylline and absorb ultraviolet light in the same wavelength region. Plasma samples spiked with 15 microng/ml theophylline and other potentially interfering drugs in therapeutic concentrations were analyzed according to the Schack and Waxler procedure. The absorbance of the alkalinized aqueous layer was read on a scanning spectrophotometer at 275 and 310 nm. Allopurinol, caffeine, phenobarbital, ampicillin and phenytoin did not appear to interfere with the measurement of theophylline. In contrast, furosemide, sulfathiazole, phenylbutazone, probenecid and theobromine produced potentially clinically significant false positive elevations of the theophylline plasma concentration. Warfarin, bishydroxycoumarin and salicylic acid produced an underestimation in the theophylline plasma concentration. The Schack and Waxler sectrophotometric method of measuring theophylline plasma concentration should be used with caution when patients are taking drugs which are weak acids which absorb in the 250-350 nm range.

Drug Interactions↗
PubMed1977

Absolute bioavailability of oral theophylline.

The absolute bioavailability of theophylline was investigated by comparing the areas under concentration-time curves for intravenous theophylline with a plain uncoated anhydrous theophylline tablet and a theophylline solution. Twenty asthmatic adults received approximately 7.5 mg/kg theophylline intravenously over 30 minutes; either seven days before or after the i.v. dose, 10 of these patients received tablets and the remainder solution in a similar dose. Blood samples were obtained at 0, 10, 20, 30, 45, 60, 90, 120, 180 and 240 minutes and then every two hours for at least 12 hours. Theophylline concentration was measured in serum by high-pressure cation exchange chromatography. The fraction of the dose absorbed averaged 0.96 +/- 0.03 for the tablet while the value for the solution was 0.99 +/- 0.02. The time of peak absorption averaged 2 +/- 0.3 hours for the tablets and 1.4 +/- 0.3 hours for the solution. The maximum serum concentration attained was 15.3 +/- 0.7 microng/ml after a dose of 7.6 +/- 0.4 mg/kg of the tablet, and 14.6 +/- 0.6 microng/ml after a dose of 7.3 +/- 0.2 mg/kg of the solution. Absorption of the tested theophylline tablets and solution approached 100% of the available drug.

Administration, Oral↗