What is the primary use for ephedrine in medicine?

The primary use for ephedrine in medicine is to treat congestion and asthma. Ephedrine is a bronchodilator, meaning it helps to widen the air passages in the lungs, making it easier to breathe. It stimulates the beta-adrenergic receptors in the lungs, which results in relaxation of the bronchial muscles. This property makes it effective for patients experiencing breathing difficulties due to conditions like asthma and bronchitis, as well as for alleviating nasal congestion by reducing swelling in the nasal passages.

In addition to helping with asthma, ephedrine's stimulant properties can also enhance airflow during respiratory distress, allowing for better oxygen intake. This is the reason it is often used in emergency situations where patients suffer from acute asthma attacks or severe respiratory distress.

Other options provided do not accurately capture the primary medical use of ephedrine. For example, while ephedrine might have secondary effects of increasing heart rate or alertness, it is not primarily prescribed for appetite stimulation, headache relief, or digestive improvement.