Medications
Nearly all glaucoma medications are are prescribed for reducing eye pressure. Lowering IOP is even proving to be beneficial for about two-thirds of patients with normal pressure glaucoma.
Beta Blockers (Timolol and Others)
Topical beta adrenoceptor blockers (common called beta blockers) are the drugs most often prescribed to treat glaucoma. They lower the pressure inside the eye by inhibiting the production of aqueous humor.
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Brands. These drugs are categorized as either nonselective or selective beta blockers:
- Nonselective adrenoceptor beta blockers. Timolol (Timoptic, Betimol) has been the standard beta blocker for years. Newer nonselective drugs are levobunolol (Betagan), carteolol (Ocupress), and metipranolol (OptiPranolol). A few studies suggest some are more beneficial than timolol with similar side effects.
- Selective beta1-adrenoceptor blockers. Betaxolol (Betoptic) and levobetaxolol (Betaxon) are selective beta blocker. These drugs appear to have fewer adverse effects on the heart than the nonselective beta blockers, although they still have widespread effects. Studies also suggest that they slow progression more than timolol does, although timolol is more effective at lowering IOP. Such findings indicate that these selective beta blockers may also have nerve-protecting properties.
All beta blockers are effective and generally well tolerated. Because they cause less eye irritation than many other glaucoma medications, they are often prescribed for patients who also have cataracts.
Side Effects and Complications. After the beta-blocker is administered, only a tiny amount of the drug is absorbed by the cornea. Most of it enters in the bloodstream. These drugs, therefore, can cause side effects in parts of the body other than the eyes, called systemic side effects:
- Common systemic side effects include reduced sexual drive, fatigue, depression, anxiety, severe nausea and vomiting, and breathing difficulties.
- Beta-blockers affect the heart. They lower heart rate and reduce blood pressure. (The newer selective beta-1 blockers may not have as adverse effects on the heart as the nonselective beta blockers.) They may also cause unhealthy cholesterol and triglyceride changes.
- All beta-blockers can worsen severe asthma or other lung diseases. Beta-blockers should only be used very cautiously or not at all by anyone with asthma, emphysema, bronchitis, or heart disease. Lung function was found to be reduced in 40% of elderly people who took timolol, even those without previous symptoms of lung problems. (Selective beta blockers may produce fewer of these adverse effects.)
- If the patient is switching to a beta blocker from other glaucoma medication, there may be a sudden rise in eye pressure. It is important, therefore, that the pressure be checked shortly after the other drug has been withdrawn.
- When beta blockers are used to treat one eye, the other (contralateral) eye also experiences a lesser, but still significant reduction in IOP.
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