Pharmacodynamics (lung function tests, tremor measurements and cAMP determinations) of a single dose of 0.5 mg terbutaline subcutaneously during sustained-release theophylline medication in patients with asthmatic bronchitis

A group of 10 patients with chronic asthmatic bronchitis was titrated with slow-release theophylline (Theolin Retard) to a steady state plasma theophylline level of 10 mg/l. After one week of this treatment a single s.c. dose of 0.5 mg terbutaline (Bricanyl) at 10:30 a.m was administered. Lung function at 8:15 a.m. on this day was better than on the reference day without any medication, but the differences were not statistically significant. At 11:00 p.m., 30 min after s.c. administration of terbutaline all lung function parameters (VC, FEV1, MMEF and sGaw) were significantly raised compared to the values of 8:15 p.m. cAMP levels and tremor were significantly higher after the combined medication (30, as well as 150 min after s.c. administration of terbutaline) than on the reference day. This observation implies that we have to be careful with the administration of terbutaline s.c. to patients on theophylline treatment in the daily practice of the lung function laboratory.

Steady-state pharmacokinetics and effects of a new once-daily, slow-release theophylline capsule preparation in asthma

Plasma and saliva theophylline concentrations were measured in 21 asthmatic subjects receiving chronic oral therapy with a new sustained-release theophylline capsule (K1B Riker) given as a once daily dose, after titration to achieve a before-dose concentration of 8 mg l-1 or greater, or to the maximum dose of 1200 mg of theophylline daily. Plasma concentrations rose from a mean +/- s.d. minimum concentration (Cmin) of 7.9 +/- 2.3 mg l-1 to a mean maximum of 13.6 +/- 3.3 mg l-1 at a median time of 10 h after dosing. Saliva theophylline concentrations were closely related to the plasma theophylline concentration both between and within subjects with a mean saliva to plasma concentration ratio between subjects (S/P ratio) of 0.62 (+/- 0.05) and a mean within subject coefficient of variation of 8.2% (+/- 4.5%). There was a significant but small (10%) change in the mean S/P ratio during the dosing interval. Peak expiratory flow rate (PEFR) changed slightly but significantly during the dosing interval but forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) did not. The drug was well tolerated at the dose used (600-1200 mg once daily).

The use of a single daily theophylline dose and metered-dose albuterol in asthma treatment

Sustained-release, 24-hour theophylline preparations have been formulated and may provide for convenient once-a-day dosing, although the use of such products in clinical asthma has yet to be fully established. This study compared single daily versus twice daily dosing with a 24-hour theophylline, Uniphyl, in asthma and further evaluated for the additional effect of metered-dose albuterol on each theophylline regimen. Twenty-eight patients with asthma were enrolled in this randomized crossover trial. Before enrollment, all demonstrated at least a 15% improvement in FEV1 after a beta-adrenergic aerosol and had serum theophylline levels ranging from 5 to 20 micrograms/ml with a predetermined 800 mg daily dose of Uniphyl. The patients were then randomly entered into four treatment regimens for one week each: Uniphyl, 800 mg four times a day (qd); metered-dose albuterol, active, 180 micrograms four times a day (qid); Uniphyl, 400 mg twice daily; metered-dose albuterol, active, 180 micrograms qid; Uniphyl, 800 mg qd; placebo, two puffs qid; and Uniphyl, 400 mg twice daily; placebo, two puffs qid. On the morning of the seventh day of each treatment regimen, pulmonary functions and a trough serum theophylline level were measured. The patient then received the same medication that he had taken for the preceding week. Spirometry was measured hourly, and a serum theophylline level was measured 6 hours later. The daily symptom scores, peak flow values, and pulmonary functions on the test day were similar with either single or twice daily Uniphyl dosing. Routine administration of albuterol by metered dose did not enhance asthma control in an unequivocal fashion.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of theophylline in beagle dogs and asthmatic patients after multiple oral doses of sustained-release theophylline tablet formulation

The bioavailability and pharmacokinetics of theophylline after a single intravenous administration of theophylline and multiple oral administration of a sustained-release theophylline tablet formation were studied in dogs. In addition, the pharmacokinetics of theophylline after multiple oral doses of the drug was also studied in asthmatic patients. In the intravenous administration of theophylline (5 mg/kg) to dogs, the theophylline half-life was 4.0 +/- 0.2 h. The apparent volume of distribution (Vd) and plasma theophylline clearance (CL) were 0.734 +/- 0.019 l/kg and 126.7 +/- 3.4 ml/kg/h, respectively. In the multiple oral doses of the drug in amounts ranging from 7.52 to 9.09 mg/kg, the Vd and CL were 0.765 +/- 0.021 l/kg and 111.0 +/- 2.4 ml/kg/h, respectively. The mean oral absorption rate constant (ka) was calculated to be 0.355 +/- 0.035 h-1 and the mean elimination rate constant (kel) was 0.146 +/- 0.007 h-1. The absolute bioavailability of the drug calculated by a computer fitting method was 1.08 +/- 0.07. The result suggests that the drug has complete absorption. On the other hand, the pharmacokinetic parameters in the asthmatic patients were 0.337 +/- 0.055 l/kg for the Vd, 32.55 +/- 3.48 ml/kg/h for the CL, 0.222 +/- 0.058 h-1 for the ka and 0.105 +/- 0.016 h-1 for the kel, respectively. This study indicated that the dog may be useful to predict bioavailability of a sustained-release theophylline tablet formulation in humans. However, it showed that there are differences between dogs and humans in the pharmacokinetic parameters.

Clinical significance of day-night differences in serum theophylline concentration with special reference to Theo-Dur

In two studies, 25 diurnally active patients with asthma (6 to 17 years of age) were evaluated at steady state for day-night differences in serum theophylline concentration (STC) by frequent blood sampling over two consecutive 12-hour dosing intervals while being given treatment with Theo-Dur. In both studies findings were similar; Cmax was greater and Tmax shorter after dosing at 7 A.M. or 8 A.M. versus 7 P.M. or 8 P.M., with Cmax-C min approximately 7 micrograms/ml. For the morning dosing, 22 of 25 patients exhibited Cmax within 4 hours; 23 of 25 exhibited C min 12 hours after dosing. For the evening ingestion, the situation was very different: C min occurred within the initial 4 hours in 22 of 25 patients, whereas Cmax occurred in 22 of 25 patients just before the next (morning) dose. The findings indicate that the most appropriate time to estimate Cmax in patients given Theo-Dur is within the 4 hours after morning ingestion. The best time to estimate C min is a few hours after the evening ingestion. Sampling at these times is likely to represent within 10% to 20% the actual Cmax or C min.

Effects of betamethasone on theophylline disposition in man. Are saliva values predictive of serum theophylline levels?

The pharmacokinetic interaction between betamethasone (5 mg/day for 5 days) and theophylline (3.35 mg/kg orally before and after betamethasone treatment) was studied in 13 female patients evaluating saliva and serum theophylline concentrations by means of an enzyme multiplied immunoassay technique. Betamethasone treatment did not significantly change saliva and serum theophylline levels. As regards the potential usefulness of saliva theophylline levels in predicting the concomitant serum concentrations of the bronchodilator, in spite of the significant correlation found in our study (r = 0.758; P less than 0.001), we think that, using individual saliva values, there is a poor predictive value for serum theophylline concentrations.

Application of the EXPERT consultation system to accelerated laboratory testing and interpretation

The EXPERT consultation system-building tool, a knowledge-based artificial intelligence program developed at Rutgers University, has been applied to the development of a laboratory consultation system facilitating sequential laboratory testing and interpretation. Depending on the results of a basic panel of laboratory tests, the system requests that specific secondary tests be performed. Input of these secondary findings can result in requests for tertiary testing, to complete the database necessary for interpretation. Interpretation of all results is based upon final inferences from the collected findings through a series of rules, a hierarchical network that yields an efficient production system not easily obtained through conventional programming. The rules included in this model are based upon initial results for total protein, calcium, glucose, total bilirubin, alkaline phosphatase, lactate dehydrogenase, aspartate aminotransferase, thyroxin, hemoglobin, mean corpuscular volume, and the concentrations of four drugs. Pertinent clinical history items included are jaundice, diabetes, thyroid disease, medications, and ethanol. Implementing this system in a laboratory-based accelerated testing program involving outpatients maximized the effective use of laboratory resources, eliminated useless testing, and provided the patient with low-cost laboratory information.

Theophylline toxicity in children

Sixty-five cases of theophylline toxicity in children were reviewed. Vomiting, tachycardia, and central nervous system excitation were the most common manifestations. Seizure activity occurred in four acutely intoxicated children whose serum theophylline concentrations were less than 70 micrograms/ml. Two patients experienced visual hallucinations in association with high serum theophylline levels. Dosing errors accounted for the majority of cases. Most instances of toxicity could have been avoided by more careful consideration of the patient's medication history and more diligent monitoring of serum theophylline concentrations.

Bioavailability of four slow-release theophylline formulations in the beagle dog

Theophylline was administered to six Beagles intravenously (Aminophyllin Injectable, Searle Laboratories) and orally as four sustained-release formulations (Choledyl -SA Tablets, Parke-Davis; Theo-Dur Tablets, Key Pharmaceuticals; Theo-24 Capsules, Searle Laboratories, and Slo-bid Gyrocaps, William H. Rorer, Inc.). Values were determined for mean residence time, mean absorption time, absolute bioavailability, time to peak plasma concentration, and peak plasma concentration normalized to a theophylline dose of 20 mg/kg. In this order the values found for each formulation were: Choledyl (10.2 +/- 1.8 h, 2.8 +/- 2.2 h, 63 +/- 10%, 3.9 +/- 1.0 h, 10 +/- 1.1 micrograms/ml), Theo-Dur (12.1 +/- 5.2 h, 4.9 +/- 5.3 h, 76 +/- 18% 4.7 +/- 3.1 h, 12 +/- 3.7 micrograms/ml), Theo-24 (15.6 +/- 8.9 h, 8.1 +/- 8.4 h, 30 +/- 16%, 3.6 +/- 1.7 h, 3.5 +/- 1.3 micrograms/ml), and Slo-bid (11.9 +/- 1.9 h, 4.4 +/- 1.3 h, 60 +/- 9%, 4 +/- 1.1 h, 8.6 +/- 0.8 micrograms/ml). Choledyl, Theo-Dur and Slo-bid appear to have absorption characteristics which, if given twice daily, would maintain therapeutic plasma concentrations of theophylline between 10 and 20 micrograms/ml in the dog. Of these, Theo-Dur was predicted to provide the least peak:trough fluctuation in theophylline plasma concentrations.

Once a day theophylline in chronic childhood asthma?

The therapeutic effects of either morning or evening administration of a once-daily controlled release theophylline preparation (Uniphyllin) were studied in 17 asthmatic children. Neither morning nor evening administration produced therapeutic plasma theophylline levels throughout 24h. Similarly, bronchodilation was not maintained during the same period. However, morning peak expiratory flow rates were significantly improved following evening dosage, suggesting a role for evening administration when nocturnal symptoms predominate.

Effect of cimetidine or ranitidine pretreatment on hepatic mixed function oxidase activity in the rat

This study compared the effect of single equimolar oral doses of cimetidine (100 mg/kg) or ranitidine (139 mg/kg) on rat hepatic mixed function oxidases. Cimetidine significantly (p less than 0.05) increased hexobarbital sleeping time and prolonged aminopyrine and theophylline elimination. In contrast, ranitidine did not significantly affect hexobarbital sleeping time and theophylline elimination but significantly (p less than 0.025) increased aminopyrine elimination. Aminopyrine N-demethylase activity in vitro was significantly (p less than 0.05) inhibited by cimetidine pretreatment but significantly (p less than 0.025) increased by ranitidine pretreatment. The direct addition of cimetidine or SKF 525A to the 10,000g supernatant fraction from controlled liver homogenates decreased aminopyrine N-demethylase activity, whereas the direct addition of ranitidine tended to increase aminopyrine N-demethylase activity. A significant correlation (r = 0.65, p less than or equal to 0.005) was observed between hexobarbital sleeping time in vivo and aminopyrine N-demethylase activity in vitro in the same rat. The results of this study showed that cimetidine inhibited mixed function oxidases, whereas ranitidine had no effect or tended to stimulate mixed function oxidases.

Theophylline pharmacokinetics in pregnancy

Theophylline pharmacokinetics were studied serially in five women during and after pregnancy. Theophylline protein binding was reduced to 11.1% +/- 4.7% (P less than 0.01) and 13.0% +/- 5.9% (P less than 0.01) during the second and third trimesters of pregnancy, respectively, compared with 28.1% +/- 2.8% when the patients were more than 6 months postpartum. Similar comparisons indicate that theophylline distribution volume and elimination t1/2 were increased from 30.7 +/- 4.4 L and 262 +/- 57 minutes to 36.8 +/- 4.2 L (P less than 0.05) and 389 +/- 73 minutes (P less than 0.01) in the third trimester of pregnancy. In the second and third trimesters, intrinsic nonrenal clearance was reduced to 0.82 +/- 0.25 ml/min X kg (P less than 0.05) and 0.67 +/- 0.18 ml/min X kg (P less than 0.01) compared with a remote postpartum value of 1.25 +/- 0.37 ml/min X kg. However, these reductions were offset by increases in theophylline intrinsic renal clearance so that apparent reductions in the overall unbound clearance of this drug did not reach statistical significance either during pregnancy or in the early postpartum period.

[A spectrophotometric micromethod for the study of theophylline pharmacokinetics in children with bronchial asthma]

A spectrophotometric micromethod for determination of theophylline in the blood is proposed. Theophylline pharmacokinetics was studied by the method in 71 children with bronchial asthma. Doses and the number of administrations were selected individually for 45 patients under control of blood plasma theophylline concentration. Good clinical results were obtained.

The use of a rapid theophylline assay in the ambulatory setting

The Seralyzer reflectance photometer was evaluated in three ambulatory settings. Of the total 99 assays in the pediatric general medicine clinic, 47 were below the therapeutic range, and 20 patients were noncompliant. There were 13 low and nine high levels along with 22 noncompliant patients detected from a total of 109 in the allergy clinic. The physician's office documented 43 low and four high levels along with 10 noncompliant patients from 105 assays. The mean time required for Seralyzer results in both the allergy and pediatric general medicine clinic was 13 minutes. Regression analysis of both finger-stick and venipuncture split samples indicated a strong correlation between Seralyzer results and traditional methods of assay (r = 0.94 and 0.99, respectively). The Seralyzer proved accurate, timely, and simple to operate.

Acute and chronic pharmacokinetics of asymmetrical doses of slow release choline theophyllinate in asthma

The day and night pharmacokinetics of assymetrical doses of slow release choline theophyllinate (Sabidal SR 270) were compared at day 1 and at day 4 of treatment when steady state had been achieved. Ten patients with chronic asthma were given oral choline theophyllinate 424 mg at 09.00 h and 848 mg at 21.00 h for 4 days. At regular intervals during day 1 and day 4 of treatment theophylline concentrations were measured in plasma and dried blood spots by fluorimmunoassay. Theophylline concentrations measured from dried blood spots were slightly lower than those in plasma, the difference remaining constant at all time points during day 1 and day 4 of treatment. On day 1 the mean peak plasma theophylline concentration was 5.4 +/- 1.0 (+/- s.e. mean) micrograms ml-1 4 h after the morning dose and 11.2 +/- 1.6 micrograms ml-1 4 h after the evening dose which were significantly (P less than 0.01) different. Similarly the areas under the plasma theophylline concentration-time curves at night were significantly (P less than 0.001) greater than those observed during the day. During day 4 mean peak plasma concentrations of theophylline after the morning and larger evening dose were 13.2 +/- 1.3 and 12.1 +/- 1.4 micrograms ml-1 respectively, which were not significantly different. No significant difference was observed between the areas under the plasma theophylline concentration-time curves during the day and at night. However the post-dose time to peak was significantly delayed at night (6 h) compared to the morning (2 h, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Theophylline concentration in the blood of children with persistently recurring bronchial asthma]

An antirecurrence effect of theophylline was studied in 32 children aged 3 to 12 years suffering from severe bronchial asthma. The drug dosage was determined by means of a stepwise increase of a daily dose in the range of 10-30 mg/kg/day under control of the patient's general condition and parameters of external respiratory function. Blood theophylline concentration was measured by an immunofluorescent method. The drug individual biotransformation was revealed. Euphylline proved to be a highly effective and safe antirecurrence agent in an individual selection of doses and administration regimens. Combination of theophylline with inhalation beta-adrenomimetics and corticosteroids potentiates its clinical effect without influencing biotransformation.

Conversion from intravenous to sustained-release oral theophylline in pediatric patients with asthma

A method for converting pediatric patients from intravenous aminophylline to sustained-release oral theophylline was evaluated in eight asthmatic children. The administration of Theo-Dur tablets two hours before discontinuation of a continuous intravenous aminophylline infusion resulted in a peak rise of 5.6 +/- 3.0 micrograms/ml over steady-state serum theophylline concentrations. This method of conversion is acceptable in children with equivalent oral and intravenous doses of theophylline and serum theophylline concentrations less than 15 micrograms/ml. Children with steady-state theophylline concentrations greater than 15 micrograms/ml are likely to develop concentrations exceeding the therapeutic range using this conversion method.

Lack of a sustained effect on catecholamines or indoles in mouse brain after long term subcutaneous administration of caffeine and theophylline

Short term administration of methylxanthines has been reported to alter levels and turnover rates of brain catecholamines and indoles. In the present study continuous administration of caffeine and theophylline was achieved by subcutaneous implantation of silastic tubing filled with powdered methylxanthines. Serum levels of caffeine and theophylline were monitored daily for 2 weeks by high performance liquid chromatography (HPLC) and averaged 35 microM and 7 microM, respectively. After 2 weeks of continuous exposure to methylxanthines the dopamine level and turnover rate were unaltered from control in the neostriatum, hypothalamus and cortex. Likewise the level and turnover of norepinephrine were unaltered from control in the cerebellum, hypothalamus and cortex. Also unaffected were the levels of 3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxy-3-methoxyphenylacetic acid (HVA), serotonin and 5-hydroxyindoleacetic acid (5-HIAA) in the hypothalamus and cortex. These results indicate that in mice the continuous exposure to methylxanthines has no long lasting effect on monoamine neurotransmitters in the brain.