Final answer:
The least likely drug to be used for treating an Adverse Drug Reaction (ADR) among the options provided is an antihistamine such as terfenadine. β-blockers are more commonly associated with cardiovascular treatments, while beta 2-adrenoceptor agonists and steroids are key in managing asthma and its acute attacks.
Step-by-step explanation:
The question is exploring which type of drug is least likely to be used in the treatment of an Adverse Drug Reaction (ADR). Analyzing the options provided, the least likely choice is an antihistamine such as terfenadine. In clinical practice, antihistamines are often used to treat allergic reactions, but they are not typically utilized to manage adverse reactions to medications unless the ADR is specifically related to an allergic component.
Sympatholytic drugs, or β-blockers, have a different mechanism of action; they are mostly used to treat cardiovascular conditions by blocking β-receptors associated with vasoconstriction and heart rate increases. As for asthma, drugs that open the airways wider, known as beta 2-adrenoceptor agonists (e.g., terbutaline, salmeterol), are used. Powerful anti-inflammatory agents, such as steroids (e.g., beclomethasone), are also commonly employed in the control of inflammatory conditions like asthma.
For acute conditions such as anaphylactic shock, epinephrine (adrenaline) is the drug of choice due to its ability to rapidly counteract severe allergic responses, including bronchoconstriction and blood pressure decrease.