Pointers for Beta-Blockers
Here are some of the finer points of administering beta-blockers:
- Because they can cause bradycardia, it is good practice to
record baseline heart rate and blood pressure prior to initiation
of therapy.
- Even when a patient uses a beta-blocker only in one eye, there
is often some IOP reduction in the fellow eye (usually around
20% of the result seen in the treated eye), probably because
of systemic absorption and redistribution.
- Beta-blocker side effects may in many instances be myth rather
than fact! Paul Lama, M.D., an internist and an ophthalmologist,
wrote an excellent piece in the November, 2002, American Journal
of Ophthalmology titled, “Systemic Adverse Effects of Beta-adrenergic
Blocker: An Evidence-based Assessment.” In his article, supported
with 91 references, he makes a number of eye-opening observations.
We want to share a few quotes or in-context paraphrases you
may find amazing: “This review identifies no scientific studies
supporting the development of depression, hypoglycemic unawareness,
or sexual dysfunction with systemic or ophthalmic beta-adrenergic
blockersx “Over the past ten years, there has been considerable
medical evidence in the literature challenging, in some cases,
refuting many of these reported adverse effectsx “Unfortunately,
non-peer-reviewed data and information, often produced and
disseminated as marketing tools by pharmaceutical companies,
may potentially alter prescribing patternsx “Regardless of
whether the beta-blockers can statistically lower HDL cholesterol,
the clinical impact is likely to be of relatively low importance
since low-risk patients are negligibly affected and concomitant
lipid-lowering therapy would offset the changes that occur
in higher-risk patient.”
- Most beta-blockers are non-selective; they affect both beta1
and beta2 receptors. Very generally speaking, beta2 receptors
are predominant in pulmonary tissues and the ciliary body;
beta1 receptors are predominant in cardiac tissues. Betaxolol
is a beta1 selective blocker.
- Of the non-selective beta-blockers with two dosage concentrations
(the timolols and levobunolol), the 0.5% of both have the yellow
label, and the 0.25% have blue labels. This seemingly trivial
note is sometimes helpful when a new patient who is on a glaucoma
drop doesn’t know the name or concentration of his medication.
- Since most studies have found the prostaglandins to be maximally
effective when instilled in the evening (although only slightly
more so), instillation of these drugs in the evening has become
a habit for most eye doctors. Newer studies have now shown
“time of instillation” makes no significant difference. This
gives greater lifestyle flexibility for our patients. However,
since beta-blockers are clearly best suited for morning instillation,
and are commonly used with the prostaglandins, we prefer to
continue to have our patients use the prostaglandins in the
evening. This keeps the morning schedule open in the event
beta-blocker use is concurrent or anticipated.
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