You should not use  timolol if you have asthma or other breathing disorders, or a serious heart condition such as "AV block," very slow heartbeats, or heart failure.
Before taking this medicine
You should not use timolol if you are allergic to it, or if you have:
asthma, chronic obstructive pulmonary disease (COPD), sleep apnea, or other breathing disorder;
a serious heart condition such as "AV block" (second or third degree);
very slow heartbeats; or
heart failure.
To make sure timolol is safe for you, tell your doctor if you have:
congestive heart failure;
coronary artery disease (hardened arteries);
diabetes;
overactive thyroid;
liver or kidney disease;
myasthenia gravis or other muscle disorders;
allergies (or if you are undergoing allergy treatments or skin-testing);
peripheral vascular disease such as Raynaud's syndrome; or
a condition for which you are being treated with IV heart or blood pressure medication (such as diltiazem, nicardipine, or verapamil).
It is not known whether this medicine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.
Timolol can pass into breast milk and may harm a nursing baby. You should not breast-feed while using this medicine.
Timolol is not approved for use by anyone younger than 18 years old.
How should I take timolol?
Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not use  timolol in larger or smaller amounts or for longer than recommended.
Your blood pressure will need to be checked often.
If you need surgery, tell the surgeon ahead of time that you are using timolol. You may need to stop using the medicine for a short time.
You should not stop using timolol suddenly. Stopping suddenly may make your condition worse.
If you are being treated for high blood pressure: Keep using this medicine even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medicine for the rest of your life.
If you are taking timolol to prevent migraine headaches: It may take 6 to 8 weeks of daily use before timolol is fully effective. Keep using the medication as directed and tell your doctor if you still have migraine headaches.
Store at room temperature away from moisture, heat, and light.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include slow heart rate, wheezing, trouble breathing, or fainting.
