Bradycardia caffeine, effect

Toxicants may have three effects on pulse rate bradycardia (decreased rate), tachycardia (increased rate), and arrhythmia (irregular pulse). Alcohols may cause either bradycardia or tachycardia. Amphetamines, belladonna alkaloids, cocaine, and tricyclic antidepressants (see imi-primine hydrochloride in Figure 6.12) may cause either tachycardia or arrhythmia. Toxic doses of digitalis may result in bradycardia or arrhythmia. The pulse rate is decreased by toxic exposure to carbamates, organophosphates, local anesthetics, barbiturates, clonidine, muscaric mushroom toxins, and opiates. In addition to the substances mentioned above, those that cause arrhythmia are arsenic, caffeine, belladonna alkaloids, phenothizine, theophylline, and some kinds of solvents. 

Theophylline Cellular mech like caffeine. More CNS stimulation than caffeine. Increased cardiac stimulation and diuresis. More effective bronchodilator. Bronchial asthma. Apnea and bradycardia in premature infants (unlabeled use). II M... 

B. Bradycardia or atrioventricular block is common in patients with moderate to severe hypertension associated with PPA and phenylephrine, owing to the baroreceptor reflex response to hypertension. The presence of dmgs such as antihistamines or caffeine prevents reflex bradycardia and may enhance the hypertensive effects of PPA and phenylephrine. 

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