Drugs for glaucoma
Drugs for glaucoma are used to reduce abnormally high pressure inside the eye.
Fluid is produced in the front part of the eye to maintain its shape and to nourish the tissues. To achieve a steady pressure, the fluid drains from the eye at the same rate at which it is produced. In glaucoma, abnormally high pressure develops in the eye because of an excessive build-up of fluid. This build-up is due to a defect in the internal drainage system between the iris (the coloured part of the eye) and the cornea (the transparent outer part of the front of the eye). There are two common types of glaucoma (acute and chronic) and two rarer types (secondary and congenital).
High pressure in the eye can be relieved by surgery, which usually eliminates the symptoms and limits any sight loss, or by using drugs that either increase fluid drainage from the eye or reduce the production of fluid.
Prompt treatment is necessary when glaucoma occurs suddenly (see Acute glaucoma) to avoid permanent damage to the eye. Once the condition is detected, immediate drug treatment will be given by intravenous injection, as eyedrops, or by mouth in order to reduce the pressure in the eye. If glaucoma develops gradually (see Chronic glaucoma), and is diagnosed early, eyedrops may be prescribed to reduce pressure in the eyes. The condition may be treated by long-term use of these drugs to reduce and maintain normal pressure in the eye.
|Beta-blocker drugs: Betaxolol, Carteolol, Levobunolol, Metipranolol, Timolol, Prostaglandin analogues, Bimatoprost, Latanoprost, Travoprost||Carbonic anhydrase inhibitors: Acetazolamide, Brinzolamide, Dorzolamide|
|Miotics: Pilocarpine||Other drugs: Apraclonidine, Brimonidine, Mannitol|
What are the types of drugs for glaucoma?
The types of drugs that are most commonly used in the treatment of glaucoma include beta-blockers, prostaglandin analogues, carbonic anhydrase inhibitors, and miotics. These drugs act in various ways to lower pressure inside the eye.
In chronic glaucoma, a beta-blocker such as timolol may be used to decrease the amount of fluid produced inside the eye. The drug works by blocking the transmission of nerve signals that stimulate the production of fluid by certain cells in the eye.
Rarely, beta-blockers may slow your heart rate and lower blood pressure. Beta-blocker eyedrops are not usually prescribed for people who have asthma or certain heart conditions.
Prostaglandin analogues drugs
These drugs are used to treat some cases of chronic glaucoma. Available as eyedrops, prostaglandin analogues work by increasing the outflow of fluid from the eye, thereby lowering the pressure inside the eye.
Side effects of prostaglandin analogues tend to be minimal; they include changes in the colour of the iris and increased thickness and length of the eyelashes. Rarely, the drugs may cause headaches and may worsen asthma.
Carbonic anhydrase inhibitors drugs
This type of drug is often used in cases of acute glaucoma. The drugs may also be used to treat chronic glaucoma if other drugs are not effective. Carbonic anhydrase inhibitors rapidly reduce fluid pressure inside the eye by blocking an enzyme necessary for fluid production. Some carbonic anhydrase inhibitors may be given as eyedrops, while others, such as acetazolamide, are given by intravenous or by intramuscular injection or are taken orally.
Carbonic anhydrase inhibitors used as eyedrops may cause stinging, itching, and inflammation of the eye. If you are having carbonic anhydrase inhibitors by injection or taking the drugs orally, you may experience loss of appetite, drowsiness, and painful tingling in the hands and feet. You may also experience mood changes. In rare cases, carbonic anhydrase inhibitors may cause the formation of kidney stones.
Both acute and chronic glaucoma can be treated using a miotic, such as pilocarpine. Miotic drugs cause the pupil to constrict, thereby moving the iris away from the cornea. This increases the size of the opening (the drainage angle) through which fluid flows out of the eye. Miotics are usually administered as eyedrops.
While taking miotics, you may find it harder to see in dim light because the drugs constrict the pupil. You may also experience irritation of the eye, blurred vision, and headache.
Various other drugs are used to treat glaucoma. For example, brimonidine reduces pressure in the eye by both decreasing the production of fluid and increasing the outflow of fluid from the eye. Mannitol encourages excess fluid to be absorbed from the eye into surrounding blood vessels. It may be given by intravenous infusion as emergency treatment for acute glaucoma or to relieve pressure within the eye just before surgery.
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