Beta Adrenergic Receptor Antagonists (Beta Blockers)
Keep in mind that about 10% of patients do not respond
to beta-blockers. This is an excellent reason to always
do a monocular therapeutic trial to firmly establish
effectiveness prior to committing a patient to bilateral
therapy. While the monocular trial is not 100% reliable
because of possible diurnal irregularities within an
individual, it is a sound therapeutic maneuver and
one that is heavily and consistently substantiated
in the medical literature.
See the literature
review section for an updated perspective
on this topic. |
Topical beta-blockers remain major workhorses in glaucoma
care, and can continue to be a first-line drug for glaucoma
patients. Because this class of drugs has a successful 25-year
track record, is the most cost-effective therapy, and
can be
effectively used “once-a-day,” it will
remain a major player
until newer, better medications are developed.
All beta-blockers act by a similar mechanism—they inhibit
aqueous formation by blocking beta2 receptors on nonpigmented
ciliary epithelium. Non-selective beta-blockers block both
beta1 and beta2 receptors; selective beta-blockers predominantly
block beta1 receptors.
The non-selective beta-blockers are all similar in efficacy,
causing about a 25% reduction in IOP. We now know that the most
commonly prescribed beta-blockers—timolol and levobunolol—are
just as effective, because of their half-lives, taken as one
drop of 0.25% solution once daily in the morning as 0.5% solutions
taken bid. (An exception is a patient of African descent, who
may require 0.5% qd.)
Simple math shows the bid 0.5% regimen, which most glaucoma
patients take, amounts to considerable overdosage, not to mention
twice the expense and dosage complexity compared to qd therapy.
Choosing the most appropriate beta-blocker sometimes simply
comes down to personal preference. There are some distinctions,
however, which we will point out here. Keep in mind that 10
to 20% of patients do not respond to beta-blockers.
Also, bear in mind that these drugs are not without potential
side effects. Because beta receptor blockage of the pulmonary
tissues can result in bronchospasm, use of beta-blockers is
contraindicated in asthmatic patients. It is also wise to avoid
these with patients having significant heart disease. At least
consult with such a patient’s physician prior to prescribing
a beta-blocker. Also, keep in mind that if the patient is taking
a beta-blocker systemically, the efficiency of topical beta-blocker
therapy can be significantly muted (see "Commonly
Prescribed Oral Beta-Blockers") .
To minimize the patient’s cost of therapy, we recommend using
sample bottles for all initial therapeutic trials. Be sure
to have the manufacturer of your drug(s) of choice keep you
well supplied with adequate samples in order to be able to
conduct these preliminary trials. This may require written
and verbal inquiries to the drug companies, but this is an
achievable goal. Once a course of therapy has been selected,
write a prescription for the largest bottle available—either
a 10 or 15ml bottle. Although 5ml bottles are available, we
rarely write for them, because they are relatively more expensive.
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