Labetalol, used to treat high blood pressure, can cause dizziness, nausea or indigestion, nasal stuffiness, fatigue and tingling of the scalp, according to Drugs.com. Less commonly, severe reactions such as allergies, chest pain or irregular heartbeat may occur.
Additional, less common side effects include dark urine, fever or chills, changes in mood, muscle pain and pale stool. These and other rare side effects such as loss of appetite and severe abdominal pain require immediate medical attention, notes Drugs.com. Symptoms of overdose include fainting, seizures, severe dizziness, difficulty breathing and slow heart rate. In the case of a suspected overdose, a local poison control or emergency room should be contacted immediately.