Which of the following is NOT a characteristic of beta agonists?

The characteristic that is not associated with beta agonists is long-term use. Beta agonists, such as those used in the treatment of asthma or other obstructive airway diseases, are primarily intended for short-term relief because they can lead to tolerance when used continuously. This tolerance reduces their effectiveness over time, making them less suitable for long-term management of conditions.

Increased heart rate and improved cardiac performance reflect the actions of beta agonists on the cardiovascular system, particularly through stimulation of beta-1 adrenergic receptors. These receptors enhance myocardial contractility and overall heart function. Additionally, facilitation of diuresis can occur due to the effect of beta agonists on renal function and blood flow, which can help in the reduction of fluid overload. Thus, these characteristics are indeed associated with the pharmacological effects of beta agonists.