tailieunhanh - Toxicology A Case-Oriented Approach - part 9

Uống cà phê nhiều kinh nghiệm ợ nóng và triệu chứng này phát sinh từ việc giảm trong giai điệu của cơ thắt thực quản thấp hơn, lần lượt, dẫn đến trào ngược axit. Trong phổ biến với các methylxanthines khác, caffeine có tác dụng mạnh trên hệ thống tim mạch. Với nhịp tim nhanh ingestions lớn | taken on a chronic basis gastric mucosal erosions occur. Many coffee drinkers experience heartburn and this symptom arises from a reduction in the tone of the lower esophageal sphincter that in turn leads to acid reflux. In common with the other methylxanthines caffeine has a potent effect on the cardiovascular system. With large ingestions tachycardia dysrhythmias and extrasystoles are noted. The observed increase in heart rate is believed to be associated with small increases in blood pressure force of contraction and cardiac output. Caffeine toxicity is also manifested by many symptoms. The term caffeinism has been applied to a syndrome of long-term excessive caffeine use. Patients with this condition exhibit headache delirium palpitations and tachycardia. Often there are gastrointestinal complaints muscle twitches psychomotor agitation and possible arrhythmias. The lethal dose of caffeine is highly variable but 3 g was reported as a cause of death in at least one case. The commonly published lethal dose is 150 to 200 mg kg about 15 g for a 150-lb. man . Blood levels greater than 25 pg mL also are regarded as in the toxic range but a good correlation between blood level and toxicity does not exist. Although the major exposure of most people to caffeine is in the form of beverage coffee caffeine also has at least two medical applications. It is available over-the-counter as an aid for the prevention of sleep and has been employed for this purpose by generations of students. Vivarin and No-Doz are two such products. Some neonatalogists employ it in the treatment of apnea of prematurity. It is superior to theophylline in some ways . a much greater half-life that allows for less frequent dosing. Caffeine also has a wider therapeutic window for example there is a larger gap between doses that provide therapeutic benefit vs. those associated with toxicity. Blood levels are of some value in this application and the following guidelines are recommended Therapeutic .