The Comparative Bioavailability of Slow Release Oral Theophylline Preparations

Edwards, C. A.; Cope, A. S.; Jackson, A. H.; Purkiss, R.

doi:10.1111/j.1365-2710.1983.tb00897.x

Cited by 3 publications

(3 citation statements)

References 17 publications

(13 reference statements)

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“…where D is the diffusion coefficient (cm 2 /s) at the given temperature and x is the membrane thick- 3 2.5 1.75 0.050 (IA) 1 2.5 0.75 0.025 (IA) 2 2.5 1.25 0.040 (IA) 3 2.5 1.75 0.050…”

Section: Diffusion Measurementsmentioning

confidence: 99%

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The diffusion and bulk properties of polyurethane (PU) ‐based hydrophilic and hydrophobic membranes

Pulat

Akdoğan

2002

J of Applied Polymer Sci

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ABSTRACT:In this study, the diffusion characteristics of diclofenac-Na through hydrophobic and hydrophilic polyurethane (PU)-based membranes are investigated. Hydrophilic polymers are obtained by graft copolymerization of PU with acriylamide (AAm) and itaconic acid (IA). The membranes are prepared by a solvent-casting method and characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis. The diffusion measurements are performed using a diffusion cell for 10 h at 37°C. Permeability coefficients calculated from diffusion experiments are ϳ3 times higher in hydrophilic membranes than hydrophobic PU membranes.

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“…where D is the diffusion coefficient (cm 2 /s) at the given temperature and x is the membrane thick- 3 2.5 1.75 0.050 (IA) 1 2.5 0.75 0.025 (IA) 2 2.5 1.25 0.040 (IA) 3 2.5 1.75 0.050…”

Section: Diffusion Measurementsmentioning

confidence: 99%

“…The use of polymers as vehicles for controlled release of drugs is a young, vigorous field. 1–3 Polymers release drugs by four general mechanisms: diffusion, chemical control, solvent activation, and magnetism. 4 The most common mechanism is diffusion consisting of matrix or reservoir (membrane) systems.…”

Section: Introductionmentioning

confidence: 99%

The diffusion and bulk properties of polyurethane (PU) ‐based hydrophilic and hydrophobic membranes

Pulat

Akdoğan

2002

J of Applied Polymer Sci

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“…The bioavailability of six different slow release oral theophylline preparations designed for 12-hourly administration has been shown to be identical, suggesting that none has advantage over the others (42). There have been no clinical studies to show that there is any synergy between beta-2 agonists and theophylline when both are given in optimal doses to those with stable asthma or acute severe asthma (43).…”

Section: T H E O P H Y L L I N Ementioning

confidence: 99%

Therapeutic Progress—review Xi.

Green

1984

J Clin Pharm Ther

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Nowadays the pharmaceutical industry provide us with a wide range of drugs for use in asthma. If these are prescribed appropriately and then used as they are intended) most patients can expect great relief of their symptoms and their doctors can find much satisfaction and indeed fun, in managing the malady. Unhappily there is evidence to show that all too often prescribing is not appropriate and the drugs are misused by those who receive them. A recent investigation of 179 wheezy Tyneside children (1) disclosed that only 21 of them or their parents had been told they had asthma and in the absence of a diagnosis, under-treatment was inevitable. Two-thirds had never received a bronchdilator and when simple prophylactic therapy was eventually given, school absenteeism fell 10-fold. The likely reason for the failure to issue the correct diagnosis is the reluctance of some to label children as asthmatics who clearly are, for fear of generating alarm, an archaic view now that the disease can so often be mastered. The British Thoracic Association's enquiry into deaths from asthma in two regions of the United Kmgdom (2) found underprescribing, patients inadequately informed about their illness and less than 50% of the patient? had co-operated satisfactorily in their management. Among others who have expressed concern, Seaton (3) highlighted misdiagnosis, outmoded drug combinations, under-use of bronchodilators due m a d y to an unreasoned fear of overdosage, under-use of steroids and failure to educate patients.Poor technique in the use of their metered-dose inhalers by asthmatics has been the subject of a number of investigations (4-6). One of the most recent (7) found only 9.5% of those assessed could use their pressurized inhalers entirely satisfactorily. It is of course, the prescribing doctor who should ensure rhat his patient is fully informed as to how and when he should use his medicaments) but the pharmacist too can play an important role in reinforcing his instructions and be prepared to answer questions when a patient is in doubt (8)(9)(10).The purpose of this article is to look at those preparations that are commonly employed in the treatment of asthma and are of proven benefit, and to discuss how they may be employed to good effect. No claim is made that there is just one correct manner in which to treat an individual, experts do differ over details (1 1) and this is of no matter providing D E V I C E S FOR I N H A L I N G D R U G SThe inhaled route is by far the best for delivering drugs in the day-to-day management of an asthmatic since it ensures the drug reaches the site at which it is needed and, as the total body dose is kept low, side-effects are minimized. Newman and his colleagues reviewed the problems encountered and suggested remedies ( 12).Metered pressurized aerosol inhalers deliver between 25 and 100 pl of drug suspended in a fluorocarbon propellant. By activation of a valve, a proportion is carried to the lungs by the patient's inspired airflow. In order to reach the bronchi, the size of the...

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