Relationship between rate and extent of absorption of oral theophylline from Uniphyl brand of slow-release theophylline and resulting serum concentrations during multiple dosing

Comparative pharmacokinetics of morning and evening doses of once-a-day theophylline capsules

The objective of this study was to determine if the theophylline diurnal variation that has been observed primarily between morning and evening doses of twice-a-day products could be overcome by a once-a-day formulation. Eighteen healthy, nonsmoking, adult male subjects were given 900-mg theophylline doses as three 300-mg once-a-day theophylline capsules in the morning or evening for 5 days in a single-blind fashion. Matching placebo capsules were administered midway between each dose of active drug. Predose theophylline serum levels on day 3-6 were statistically equivalent within each treatment, indicating that approximate steady-state conditions were achieved by day 3. Mean serum level profiles over the 24-h interval following the active dose on day 5 were almost superimposable for the morning and evening treatments. All pharmacokinetic parameters were equivalent between the treatments, except for the time to peak serum level (Tmax), which was significantly shorter for the morning dose. Given the flatness of the serum level curves for both treatments, the Tmax difference was judged to be clinically unimportant. A small peak-trough level fluctuation of about 50% was seen with each treatment. We conclude that by designing a dose form in which drug release was the rate-limiting step in drug absorption, the diurnal variation commonly associated with theophylline formulations may be eliminated.

Theophylline toxicity

Theophylline toxicity continues to be a commonly encountered clinical problem. Patients may present with a vast array of toxic manifestations, including life-threatening cardiovascular and neurologic toxicity. Despite the considerable attention this topic has received in the literature, there remain some important controversies regarding the identification of high risk patients and how best to manage them. This review attempts to summarize the current state of knowledge regarding theophylline toxicity with special emphasis on toxic manifestations and the role of elimination enhancing modalities.

Theophylline-controlled release preparations and fatty food: an in vitro study using the rotating dialysis cell method

The in vitro dissolution behavior of four controlled-release theophylline products was investigated utilizing the rotating dialysis cell method. The effects of pH, oil, and enzymes on the dissolution profiles were studied. The wide range of pH values and the content of oil and enzymes in the dissolution media in the dialysis cell, which functioned as an in vitro model, were simulated to mimic physiological changes due to food along the entire gastrointestinal tract. Treatment with oil affected the dissolution behavior of Uniphyl and especially Theo-Dur Sprinkle but had little or no effect on the dissolution profiles of Theo-Dur tablets and Theo-24 capsules. The in vitro observations of the oil effect were related to the food effect obtained from published in vivo studies. The rotating dialysis cell can be a useful tool in studying factors which may be responsible for dissolution-related food effects on the absorption of controlled-release products.

Antiasthmatic therapy in children

The availability of more and better medications for asthma contrasts with reports of an increasing frequency of hospitalization and fatalities. An understanding of the pathophysiology of the disease, its variations in clinical patterns, and the therapeutic potential of the available options for treatment in this overview of asthma management provides a basis for addressing this paradox. A scheme for matching the therapeutic options to the clinical pattern of the disease is presented with comments on the delivery of health care to asthmatic patients. Results of outcome from comprehensive asthma management programs are described.

Influence of hyperlipidic food on the kinetics of slow-release formulations of theophylline

A cross-over study of kinetics has been undertaken in 12 healthy adults volunteers using two sustained-release theophylline products that allow once a day dosing (Theo-Dur tablets and Dilatrane A.P. bead filled capsules) to compare the i.v. pharmacokinetic profiles when taken with an hyperlipidic meal and a balanced standard meal. Each subject took part in four phases in randomised order, corresponding to all possible combinations of the products and the types of meal. Each phase involved a single dose of 9 to 11 mg.kg-1 theophylline administered at 20.00 h, at the beginning of the meal, with 100 ml water. The two formulations were found to be bioequivalent with both types of meal. Taken with a balanced meal, the mean parameters were similar; for Theo-Dur and Dilatrane A.P. they were respectively: Cmax: 11.32 mg.l-1 which plateaued from 8 to 10 h after dosing and 10.9 mg.l-1, which plateaued after 6 to 10 h; AUC 230 mg.h.l-1 and 220 mg.h.l-1; and MRT 18.2 h and 17.7 h. After the hyperlipidic meal the values for Theo-Dur and Dilatrane A.P. respectively, were: Cmax 10.9 mg.l-1 at 12 h and 11.3 mg.l-1 at 10 h; AUC 237 mg.h.l-1 and 227 mg.h.l-1; and MRT 19.2 h and 18.9 h. In spite of a decrease in the absorption rate, which led to a shift to the right of about 2 h of the plasma concentration-time curve, the bioavailability of both formulations were not significantly modified by a hyperlipidic meal as compared to a balanced meal.(ABSTRACT TRUNCATED AT 250 WORDS)