Local anesthetics beta-blockers

Small quantities of adrenaline, such as are present as an additive in local anesthetic formulations, can be dangerously potentiated by beta-adrenoceptor blockers propranolol should be discontinued at least 3 days in advance of administering such products for local anesthesia. A combined infusion of adrenaline and propranolol has been used for diagnosing insulin resistance, but it can evoke cardiac dysrhythmias, even in patients without signs of coronary disease (17). 

Clinically important, potentially hazardous interactions with beta-blockers, local anesthetics, muscle relaxants... 

Membrane stabilizing activity (MSA) Local anesthetic action typical of several beta-blockers, eg, propranolol... 

A. Classiflcation, Subgroups, and Mecbanisms All of the clinically used beta-blockers are competitive phanuacologic antagonists. Propranolol is the prototype. Drugs in this group are usually classified into subgroups on the basis of P, versus P selectivity, partial agonist activity, local anesthetic action, and lipid solubility (Table 10-2). 

Local anesthetic activity Local anesthetic activity ( membrane stabilizing activity ) is a disadvantage when beta-blockers are used topically in the eye because it decreases protective reflexes and increases the risk of corneal ulceration. Local anesthetic effects are absent from timolol and several other beta-blockers. 

A. Prototypes, Mechanisms, and Effects Beta-blockers are discussed in more detail in Chapter 10. Propranolol and esmolol are the prototype antiarrhythmic beta-blockers. Their mechanism in arrhythmias is primarily cardiac beta blockade and reduction in cAMP, which results in the reduction of both sodium and calcium currents and the suppression of abnormal pacemakers. The AV node is particularly sensitive to beta-blockers the PR interval is usually prolonged by class II drugs (Table 14-2). Under some conditions, these dmgs may have some direct local anesthetic (sodium channel-blocking) effect in the heart, but this is probably rare at the concentrations achieved clinically. 

Nonselective beta-blocker prototype local anesthetic action but no partial agonist effect. Used in HTN, angina, arrhythmias, migraine, hyperthyroidism, tremor. Tox asthma, AV block, CHF. 

---