Sympatholytics p-Blockers

Undesired effects. p-Blockers are used very frequently and are mostly well tolerated if risk constellations are taken into account. The hazards of treatment with p-blockers become apparent particularly when continuous activation of p-receptors is needed in order to maintain the function of an organ. 

On the other hand, convincing clinical evidence demonstrates that, under appropriate conditions (prior testing of tolerability, low dosage), p-blockers are able to improve prognosis in congestive heart failure. Protection against heart rate increases and arrhythmias may be important underlying factors. 

Bradycardia, AV block. Elimination of sympathetic drive can lead to a marked fall in cardiac rate as well as to disorders of impulse conduction from the atria to the ventricles. 

Bronchial asthma. Increased sympathetic activity prevents bronchospasm in patients disposed to paroxysmal constriction of the bronchial tree (bronchial asthma, bronchitis in smokers). In this condition, p2-receptor blockade may precipitate acute respiratory distress (B). 

Altered vascular responses When ( -receptors are blocked, the vasodilating effect of epinephrine is abolished, leaving the a-receptor-mediated vasoconstriction unaffected cold hands and feet.  

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