When caring for a client with an upper respiratory infection (URI), the nurse is notified the client is taking guaifenesin (Mucinex). What is the mechanism of action of guaifenesin (Mucinex)?

The correct answer is D: Loosen bronchial secretion to assist in elimination. Guaifenesin works as an expectorant by increasing the volume and reducing the viscosity of respiratory tract secretions, helping to clear mucus and make coughing more productive in clients with URI. Choices A, B, and C are incorrect as they do not describe the mechanism of action of guaifenesin. Option A refers to a vasoconstrictive action, which is not the function of guaifenesin. Option B mentions competing with histamine, which is the mechanism of antihistamines, not expectorants like guaifenesin. Option C is related to treating allergic rhinitis and motion sickness, not the intended action of guaifenesin in URI.