Let us now know about some of the essential drugs that some way or the other help people to get a respite from the pain of glaucoma, or to some extent reduce the pressure if not get a complete cure.
There are two primary mechanisms for lowering eye pressure:
1) Decrease the amount of aqueous humor coming into the eye i.e. reduce the production of aqueous,
2) Increase the amount of aqueous leaving the eye i.e. increase the outflow of aqueous. Some medications decrease the production of aqueous humor whereas others increase the outflow.
Aqueous humor flows out of the eye using two pathways: one that is sensitive to eye pressure (the trabecular meshwork pathway) and one that operates independently of eye pressure (the uveoscleral pathway).
From all of the available choices, a reasonable initial approach would be to choose an eyedrop that will get the eye pressure as low as safely possible in each particular patient. The choice of the initial agent is guided by the patient characteristics and associated medical conditions.
The guiding principal is to avoid known side effect issues while maintaining the convenience of once a day administration to maximize compliance. The initial eyedrop could be Timoptic, Xalatan or Alphagan.
Glaucoma Treatment-An Evolving Paradigm
Each patient must then be monitored routinely to ensure that IOP is maintained at a level low enough to prevent glaucomatous progression. If additional eye pressure lowering is required then it is best to add an eyedrop with a different mechanism of action than the initial drug. For example, if the initial eyedrop used is Xalatan which works by increasing uveoscleral output, then the second eyedrop could be Timoptic or Trusopt which work by decreasing aqueous humor production. We discuss below the key points in considering the drug treatment. We have used brand-names because of general familiarity with the names, although several drugs are available in equally effective and cost effective generic forms.
Beta blockers (Timoptic, Timoptic (XE/GFS, or Ocudose), Betoptic, Optipranolol, Ocupress)
Beta-blockers are still the most popular anti-glaucoma agents, and they far surpass any other medication as the first therapy of choice in open-angle glaucoma. Although beta blockers have proven to be very effective and safe when used as eyedrops, there are several long-term side effects that one needs to be aware of.
In general side effects are more associated with non-selective beta blockers (Timoptic) than with selective beta blockers (Betoptic). However, Timoptic pressure lowering affect is more efficacious than Betoptic. The non-selective beta-blocker Timoptic lowers the Eye pressure by 4-6 mm Hg (20-35%), and Betoptic lowers eye pressure by 3-4 mm Hg (15-25%).
Beta blockers can cause bronchospasm and thus can exacerbate asthma and chronic obstructive pulmonary disease (COPD). It may be worthwhile to avoid beta blockers in patients who smoke and in patients with a history of bronchospastic disorders (selective beta blocker, Betoptic may still be used). Beta blockers should be used with caution in diabetics because they may mask the symptoms of hypoglycemia.
Bradycardia (reduced heart rate) is another potential side effect. Since myocardial contractility is reduced, these agents can exacerbate congestive heart failure. These agents should be used with caution in any patient with heart disease. Recently reports suggest that beta-blocking agents are associated with nocturnal hypotension, which may be a risk factor in progression of glaucomatous optic nerve damage.
After prolonged use, depression, mood alterations, memory loss, hallucinations, decreased libido, and impotence can all occur. An easy and effective way to reduce systemic side effects of timoptic is to perform nasolacrimal occlusion after topical application. Nasolacrimal occlusion reduces plasma levels of timoptic by up to 70%. Betimol also has Timolol (like in Timoptic).
Prostaglandin analogues (Xalatan, Rescula, Travatan, Lumigan)
These prostaglandin-like drugs lower intraocular pressure by increasing the uveoscleral outflow of aqueous humor. They are very effective in reducing the eye pressure and have the advantage of requiring only once a day administration. The prostaglandin analogs (Xalatan) lower IOP by up to 50% and 6-8 mm Hg on average.
Current trend clearly shows Xalatan to be emerging as the favored first-line eye pressure reducing drug. Rescula is not quite as effective and is only able to lower the eye pressure by 3-4 mm Hg. The prostaglandin analogs seem to be more effective in eyes with dark colored iris.
Unopened bottles of Xalatan require refrigeration but after opening it one can keep the opened bottle at room temperature if the bottle is going to be used up within a month. The Use of Xalatan has been reported to be associated with exacerbation of uveitis and cystoid macular edema. Of some concern is the ability of these agents to cause permanent iris color changes. Blue/green iris color may become brownish. These agents should also be avoided in pregnant women because of the potential of prostaglandins to induce labor.
Alpha-Adrenergic Agonists (Alphagan, Iopidine, Propine)
These drugs work by both increasing uveoscleral outflow and by decreasing aqueous formation. They require twice-daily administration to be effective. Alphagan can reduce eye pressure by approximately 20-27%. Alphagan has also neuroprotective properties.
Though the evidence is far from being definitive, experimental studies show that alphagan prevents degeneration of retinal nerve cells. Allergy rate of 30% has been observed with Alphagan.
A new formulation, Alphagan-P has Purite as the preservative and this formulation may decrease the incidence and severity of allergic reactions. Othe side effects include conjunctival hyperemia (the eye appears red) along with conjunctival follicle formation. Severe hypotension and other cardiovascular side effects have been reported in infants and toddlers. Alphagan is contraindicated in infants because of serious systemic side-effects and should be avoided in children under 5 years of age.
Carbonic anhydrase inhibitors (Trusopt, Azopt)
These drugs decrease intraocular pressure by reducing aqueous formation. Although slightly less effective than the beta-blockers, these agents are usually well tolerated. If used as monotherapy, they may require three-times daily dosing, but twice-daily dosing is usually efffective when they are used as adjunctive treatment.
These are sulfa-drugs so patients allergic to sulfonamides should not use them.Serious side effects are rare, but kidney stones, corneal decompensation, hypotony, and choroidal detachment have been reported in patients using topical carbonic anhydrase inhibitors. A metallic or distorted taste, particularly with carbonated beverages, may be experienced.
Oral carbonic anhydrase inhibitors are also available (Diamox, Neptazane).
Combination eyedrops (Cosopt)
Currently combination of Timoptic and Trusopt (Cosopt) is available and is very effective in twice a day dosing. Combinations of Xalatan and Timoptic as well as Alphagan and Timoptic are being studied and may become available soon. Combination eyedrops may improve compliance if more than one drug is needed to control the eye pressure as it is more convenient to deal with just one bottle.
Peripherally selective 5-HT2A agonists such as the indazole derivative AL-34662 are currently under development and show significant promise in the treatment of glaucoma.
Another compound which is a very household name among the smokers Marijuana, has also showed to be effective in lowering IOP pressure. But it is still not recommended for medical use. And we also would not like our readers to smoke marijuana to get respite from the pain of glaucoma.
Other than these drugs, marijuana is being tested and still under research since it has been reported to reduce intraocular pressure. Also the doctors recently have reported that caffeine has been found responsible for increase of eye pressure. So its bit of concern for "coffee aholics".
Filed under Cataract Surgery, Eye Care Products, Eye Treatment, Glaucoma | Tags: Alpha-Adrenergic Agonists, aqueous humor, beta blockers, bradycardia, caffeine, Carbonic anhydrase inhibitors, eye, marijuana, prostaglandin analog | Comment Below