A medication with an antitussive effect acts to do which of the following?

A medication with an antitussive effect is specifically designed to alleviate coughing. Antitussives work by suppressing the cough reflex, which can be particularly beneficial in situations where coughing is nonproductive, such as in cases of a dry cough or when coughing disrupts sleep or daily activities.

The other options, while related to respiratory health, describe mechanisms that are not the primary function of an antitussive. Increasing respiratory secretions would actually lead to more coughing, and reducing respiratory tract swelling is often the role of anti-inflammatory medications rather than antitussives. Soothe irritated throat tissues may occur with some throat lozenges or expectorants, but it is not the direct action of an antitussive. Therefore, the primary role of an antitussive medication is indeed to relieve coughing.