Do not take this medication if you are allergic to hyoscyamine, or if you have kidney disease, a bladder or intestinal obstruction, severe ulcerative colitis, toxic megacolon, glaucoma, or myasthenia gravis.
Before taking hyoscyamine, tell your doctor if you have heart disease, congestive heart failure, a heart rhythm disorder, high blood pressure, overactive thyroid, or hiatal hernia with gastroesophageal reflux disease.
Avoid taking antacids at the same time you take hyoscyamine. Antacids can make it harder for your body to absorb hyoscyamine. If you use an antacid, take it after you have taken hyoscyamine and eaten a meal.
Hyoscyamine can cause side effects that may impair your vision, thinking, or reactions. Be careful if you drive or do anything that requires you to be awake and able to see clearly.
Avoid drinking alcohol. It can increase drowsiness and dizziness while you are taking hyoscyamine.
Avoid becoming overheated or dehydrated during exercise and in hot weather. Because hyoscyamine reduces sweating, it can increase your risk of heat stroke.