Theophylline sustained-release tablets

Theophylline Sustained Release Tablets (500 mg) DC 4. Drug release... 

Meshali MM, El-Sayed GM, El-Said Y, et al. Preparation and evaluation of theophylline sustained release tablets. Drug Dev Ind Pharm 1996 22(4) 373-376. 

Polyvinyl acetate is described in the literature as a matrix former in theophylline sustained-release tablets obtained by hot-melt extrusion [646]. In a similar way spray-dried PVAc/Povidone can be applied for the production of tablets and pellets using its excellent flowability. In this case the pulverization of polyvinyl acetate by cryogenic grinding can be avoided and the mixture of the active ingredient with the excipients are applied directly to the melt extruder. 

Theophylline, a dimethylxanthine, causes broncho-dilation, possibly by inhibiting the enzyme phosphodiesterase in smooth muscle of the bronchioli. An other proposed mechanism of action is that of adenosine receptor antagonism. It has positive chronotropic and inotropic, CNS stimulant and weak diuretic properties. In obstructive lung disease sustained release tablets are to be preferred. Theophy-line has a narrow therapeutic index. Therapeutic plasma concentrations are between 7-15 mg/1. Theophylline undergoes N-demethylation via CYPl A2 in the liver and is eliminated in the urine as metabolites... 

Saraiya K, Bolton S. Use of Precirol to prepare sustained release tablets of theophylline and quinidine gluconate. Drug Dev Ind Pharm 1990 16(13) 1963-1969. 

MN Gai, A Isla, MT Andonaegui, AM Thielemann, C Seitz. Evaluation of the effect of 3 different diets on the bioavailability of 2 sustained release theophylline matrix tablets. Int J Clin Pharmacol Ther 35 565-571, 1997. 

Oral sustained-release, 24 hours 100, 200, 300 mg tablets and capsules 400, 600 mg tablets Parenteral 200, 400, 800 mg/container, theophylline and 5% dextrose for injection Other Methylxanthines Dyphylline (generic, other)... 

Boraie NA, Naggar VE. Sustained release of theophylline and aminophylline from agar tablets. Acta Pharm Jugosl 1984 34(Oct-Dec) 247-256. 

A dosage interval of 12 h appears to be appropriate to use in dogs for oral sustained-release anhydrous theophylline tablets (Koritz et al, 1986) and oral sustained-release morphine sulphate tablets (Dohoo et al, 1994). Following oral administration of these sustained-release dosage forms, the average systemic availability of theophylline is 76% and of morphine is 21%. Gastro-... 

E. Sanchez, C. M. Evora, and M. Llabres, Effect of humidity and packaging on the long-term aging of commercial sustained-release theophylline tablets, Int. J. Pharm. 83, 59-63 (1992). 

Theophylline administered in liquids or uncoated tablets is absorbed rapidly and completely. In the absence of food, solutions or uncoated tablets of theophylline produce maximal concentrations in plasma within 2 hours and maximal plasma concentrations are achieved within I hour. Numerous sustained-release preparations of theophylline are available, designed for dosing intervals of 8, 12, or 24 hours. There is marked interpatient variability in the rate and extent of absorption, and especially in the effect of food and time of administration on these parameters. Thus, it is necessary to avoid substituting one apparently similar product for another. 

Also known as bhara gum, the exudate from the incised trunk of some tropical trees of Terminalia genus (T. bellerica Roxb., T. catappa L., T. randii Baker f.), Combretaceae family, may be used in the formulation of some sustained release pharmaceutical forms famotidine microcapsules (ionic gelation technique) [296] dextromethorphan hydrobromide tablets obtained by direct compression, wet granulation and solid dispersion techniques [297] carvedilol (water insoluble) and theophylline (water soluble) tablets prepared by direct compression - Terminalia gum was assessed as controlled release matrix against xanthan gum and hydroxypropyl methylcellulose [298]. 

---