It is common for a cough from bronchitis or whooping cough to persist for several weeks, even after starting antibiotics like azithromycin, as your airways need time to heal. Since your current expectorant and bronchodilator combination (Viscodyne) is not providing relief, you should consult your doctor for a re-evaluation. They may consider alternative treatments, such as inhaled corticosteroids to reduce airway inflammation, or cough suppressants like dextromethorphan or benzonatate to help you rest. In the meantime, stay well-hydrated and use a cool-mist humidifier to soothe your airways. Seek immediate care if you experience difficulty breathing, chest pain, or a high fever.