Final answer:
Beta-adrenergic blockers, unlike dopamine, digitalis-like drugs, and calcium sensitizers, do not have a positive inotropic effect; they reduce heart contraction strength and therefore are the exception in the list of medications.
Step-by-step explanation:
Examples of medications with positive inotropic effect increase the strength of heart contractions, and they include dopamine, digitalis-like drugs, and calcium sensitizers. These drugs function by enhancing the influx of calcium ions or preventing their sequestration, thus raising intracellular calcium levels which strengthens the heart's contractions. On the other hand, β-adrenergic blockers, also known as beta blockers, typically have a negative inotropic effect by blocking the β-receptors associated with increased heart rate and contraction strength.
Therefore, the correct answer is that β-adrenergic blockers do not have a positive inotropic effect and are the exception among the options listed. Medications with positive inotropic effects are drugs that increase the strength of the heart's contractions. Examples of medications with positive inotropic effects include dopamine, digitalis-like drugs, and calcium sensitizers.