|
Glaucoma.
Drugs.
Eye drops
Intraocular
pressure can be lowered with medication, usually eye drops. There are
several different classes of medications to treat glaucoma with several
different medications in each class. Topical beta-adrenergic receptor
antagonists such as timolol, levobunolol (Betagan) , and betaxolol decrease
aqueous humor production by the ciliary body. Alpha2-adrenergic agonists
such as brimonidine (Alphagan) work by a dual mechanism, decreasing aqueous
production and increasing uveo-scleral outflow. Less-selective sympathomimetics
like epinephrine and dipivefin (Propine) increase outflow of aqueous humor
through trabecular meshwork and possibly through uveoscleral outflow pathway,
probably by a beta2-agonist action. Miotic agents (parasympathomimetics)
like pilocarpine work by contraction of the ciliary muscle, tightening
the trabecular meshwork and allowing increased outflow of aqueous through
traditional pathways. Carbonic anhydrase inhibitors like dorzolamide (Trusopt),
brinzolamide (Azopt), acetazolamide (Diamox) lower secretion of aqueous
humor by inhibiting carbonic anhydrase in the ciliary body. Prostaglandin
analogs like latanoprost (Xalatan), bimatoprost (Lumigan) and travoprost
(Travatan) increase uveoscleral outflow of aqueous. Each of these medicines
may have local and systemic side effects. Adherence to the medication
protocol can be confusing and expensive; if side effects occur, the patient
must be willing either to tolerate these, or to communicate with the treating
physician to improve the drug regimen.
Poor compliance with medications and follow-up visits is
a major reason for vision loss in glaucoma patients. Patient education
and communication must be ongoing to sustain successful treatment plans
for this lifelong disease with no early symptoms.
Marijuana has been shown to lower the intraocular pressure
in some eyes in a few studies but this is generally not used clinically.
Studies in the early 1970s showed that marijuana, when smoked, lowers
intraocular pressure in people with normal pressure and those with glaucoma.
In an effort to determine whether marijuana, or drugs derived from marijuana,
might be effective as a glaucoma treatment, the National Eye Institute
supported research studies from 1978 to 1984. These studies demonstrated
that some derivatives of marijuana lowered intraocular pressure when administered
orally, intravenously, or by smoking, but not when topically applied to
the eye. However, none of these studies demonstrated that marijuana -
or any of its components - could safely and effectively lower intraocular
pressure any more than a variety of drugs then on the market.
The first patient in the United States federal government's
Compassionate Investigational New Drug program, Robert Randall, was afflicted
with glaucoma and had successfully fought charges of marijuana cultivation
because it was deemed a medical necessity (U.S. v. Randall) in 1976.
The possible neuroprotective effects of various topical and systemic
medications are also being investigated.
|
