Glaucoma Home > Istalol Warnings and Precautions

To help minimize risks, warnings and precautions for Istalol should be discussed with your healthcare provider before starting treatment. It is important to know that Istalol can potentially worsen some conditions, such as heart failure, allergic reactions, and breathing problems. Before using Istalol, talk to your healthcare provider about any other medical conditions you have and any medications you are taking.

What Should I Tell My Healthcare Provider Before Taking Istalol?

You should talk with your healthcare provider prior to taking Istalol® (timolol maleate) if you have:
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
Make sure to tell your healthcare provider about any other medications you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.

Specific Istalol Warnings and Precautions

Some warnings and precautions to be aware of prior to taking this drug include the following:
  • Istalol should not be used alone for treating closed angle glaucoma.
  • If you will be having surgery, make sure your surgeon and anesthesiologist know you take Istalol, as it may affect the choice of medications used during the surgery.
  • Even though Istalol is an eye drop, a significant amount of the medication may be absorbed into the bloodstream. Therefore, most of the usual warnings or precautions with other beta blockers also apply to Istalol.
  • Istalol may worsen allergic reactions and can make epinephrine (one of the standard treatments for life-threatening allergic reactions) less effective. If you have a history of severe allergic reactions, Istalol (or any other beta blocker) may not be the best choice for you.
  • Like all beta blockers, Istalol can worsen heart failure in some situations. If you have heart failure, your healthcare provider may need to monitor you very closely while you take Istalol. Let your healthcare provider know immediately if your heart failure symptoms seem to worsen.
  • Beta blockers can worsen breathing problems like asthma or COPD. In many cases, Istalol is not recommended for people with such lung problems.
  • Istalol may worsen myasthenia gravis symptoms or may even potentially cause myasthenia gravis. Let your healthcare provider know if you develop symptoms of this problem, such as muscle weakness, double vision, or a droopy eyelid.
  • Beta blockers can mask some of the symptoms of low blood sugar (hypoglycemia), particularly the "racing heart" feeling. This can cause serious problems for people with diabetes, who need to be able to sense that they have low blood sugar (in order to correct it before it becomes life-threatening). Some beta blockers may also worsen low blood sugar levels, although it is not known if this is a problem for Istalol.
  • Beta blockers can mask some of the symptoms of an overactive thyroid (hyperthyroidism).
  • Istalol can potentially interact with a number of other medications (see Istalol Drug Interactions).
  • Istalol is considered a pregnancy Category C medication. This means that it may not be safe for use during pregnancy, although the full risks are not currently known (see Timolol and Pregnancy).
  • It is not known if Istalol passes through breast milk in humans. Therefore, if you are breastfeeding or plan to start breastfeeding, discuss this with your healthcare provider prior to taking the drug (see Timolol and Breastfeeding).
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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