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Theophylline, một alkaloid hiện diện tự nhiên trong trà và cà phê, được sử dụng rộng rãi trong điều trị hen suyễn nhiều hơn năm mươi năm. Tác dụng giãn phế quản tối ưu là chỉ nhìn thấy với một mức độ huyết tương từ 10-20 mg / l | THEOPHYLLINE Use Theophylline given IV as aminophylline is a useful respiratory stimulant in babies with neonatal apnoea but caffeine q.v. is the drug of choice because it has a wider safe therapeutic range. Pharmacology Theophylline a naturally occurring alkaloid present in tea and coffee was widely used in the treatment of asthma for more than fifty years. The optimum bronchodilator effect is only seen with a plasma level of 10-20 mg l but toxic symptoms are sometimes seen in the newborn when the level exceeds 14 mg l and gastro-oesophageal reflux may be made worse. Sustained use increases urinary calcium loss. Very high blood levels cause hyperactivity tachycardia and fits that seem to respond to the oral administration of activated charcoal even when the drug has been given IV. Correct any hypokalaemia or metabolic acidosis. Arrhythmias that fail to respond to adenosine q.v. may respond to propranolol q.v. . A single prophylactic 8 mg kg IV dose seems to reduce some of the adverse renal consequences of perinatal asphyxia. Theophylline is moderately well absorbed in the neonate when given by mouth but slowly metabolised by a series of parallel liver pathways some of which are saturable. The neonatal half life 15-50 hours is five times as long as in adults. There is no evidence that moderate maternal use during pregnancy or lactation is hazardous to the baby although calculations suggest that a breastfed baby might receive on a weight-for-weight basis about an eighth of the maternal dose. Caffeine has many advantages over theophylline in the management of neonatal apnoea. The gap between the optimum therapeutic blood level and the blood level at which toxic symptoms first appear is much wider with caffeine than it is with theophylline and caffeine usually only needs to be given once a day. Theophylline is in any case partly metabolised to caffeine in the liver in the neonatal period. Drug interactions Toxicity can occur in patients also taking cimetidine .
