Aellig W H
J Cardiovasc Pharmacol. 1983;5 Suppl 1:S16-20. doi: 10.1097/00005344-198300051-00003.
Despite their common property of competitive beta-adrenoceptor blockade, beta-adrenoceptor blocking drugs differ in the presence or absence of several ancillary properties. One of these is partial agonist activity [intrinsic sympathomimetic activity (ISA)]. Drugs of this type are as effective in inhibiting beta-adrenoceptor stimulation as are drugs devoid of ISA, but unlike the latter they produce some stimulation of beta-adrenoceptors. This stimulating activity is sufficient to compensate partly or totally for the loss of resting sympathetic drive resulting from blockade of beta-adrenoceptors. Increases in heart rate during physic and psychic stress, however, are reduced to practically the same extent by all beta-adrenoceptor blocking drugs, whether they possess ISA or not. With pindolol the maximum stimulatory activity is reached at very low doses. Over a dose range wider than that used in clinical practice, the effect of pindolol on resting heart rate is therefore not dependent on the dose but on the heart rate before drug administration. Pindolol is a drug with sufficient ISA to compensate for blockade of sympathetic drive at rest. It therefore does not influence or only slightly reduces normal resting heart rate and cardiac output, and thus does not give rise to reflex increases in total peripheral resistance. During chronic oral treatment of hypertension with pindolol, peripheral resistance is usually reduced.
尽管β肾上腺素受体阻断药具有竞争性β肾上腺素受体阻断的共同特性，但它们在是否存在几种辅助特性方面存在差异。其中之一是部分激动剂活性[内在拟交感活性（ISA）]。这类药物在抑制β肾上腺素受体刺激方面与缺乏ISA的药物一样有效，但与后者不同的是，它们会对β肾上腺素受体产生一定的刺激作用。这种刺激活性足以部分或完全补偿因β肾上腺素受体阻断导致的静息交感神经冲动丧失。然而，在生理和精神应激期间，所有β肾上腺素受体阻断药，无论是否具有ISA，均可将心率升高程度降低至几乎相同的水平。对于吲哚洛尔，在非常低的剂量时即可达到最大刺激活性。因此，在比临床实践中使用的剂量范围更宽的剂量范围内，吲哚洛尔对静息心率的影响不取决于剂量，而是取决于给药前的心率。吲哚洛尔具有足够的ISA来补偿静息时交感神经冲动的阻断。因此，它不会影响或仅轻微降低正常静息心率和心输出量，从而不会引起总外周阻力的反射性增加。在用吲哚洛尔长期口服治疗高血压期间，外周阻力通常会降低。
