A Fresh
Look at "Sulfa Allergy"
July 2004.
There has long been a history of concern over placing patients
with “sulfa allergy” on sulfa-based drugs such as carbonic
anhydrase inhibitors used in the management of both open- and
closed-angle glaucoma, as well as pseudotumor cerebri.
Acetalzolamide (Diamox), methazolamide (Neptazane), brinzolamide
(Azopt) and dorzolamide (Trusopt) are commonly used in eye
care.
“Acetalzolamide is a mainstay in the medical treatment of
idiopathic intracranial hypertension (pseudotumor cerebri).
It is a nonbacterial sulfonamide with a chemical structure
and pharmacological activity that is different from the sulfonamide
antimicrobials.”
“The unfortunate lay term ‘sulfa allergy’ has been used to
describe any allergic or pseudoallergic reaction to sulfonamides,
but clinically it usually (if not exclusively) refers to a
reaction to sulfonamide antibiotics.”
“A detailed medical history, documentation of the type of
adverse reaction, adequate patient counseling regarding the
low but theoretical risk of cross-reaction, and appropriate
informed consent are recommended for these patients.”
Reference:
Lee, A. G., et. al. “Presumed ‘Sulfa-allergy’ in Patients
with Intracranial Hypertension Treated with Acetalzolamide
or Furosemide: Cross-reactivity, Myth or Reality?”. AJO,
July, 2004
An abstract appearing in the July, 2004 AJO on this same topic
concluded: “This study shows that although there is an association
between hypersensitivity after receipt of sulfonamide antibiotics
and a subsequent reaction after the receipt of a sulfonamide
nonantibiotic, the association appears to be due to a predisposition
to allergic reactions rather than to cross-reactivity with
sulfonamide drugs.”
Reference:
Storm, B. L., et. al. “Absence of Cross-reactivity Between
Sulfonamide Antibiotics and Sulfonamide Nonantibiotics.”
English Journal of Medicine, 2003; 349: 1635-1638.
M & T Commentary
In treating patients with acute angle closure glaucoma, or
iatrogenically-induced bilateral simultaneous angle closure
(such as with Topamax), we have long held that patient with
a history of sulfa-allergy not be treated with acetalzolamide
(Diamox), but rather with glycerin (Osmoglyn). This guidance
may be overly cautious in light of the new findings set forth
in these articles. For non-diabetic patients, this advice
may well continue to be the rational, albeit, conservative
approach. However, for those less common patients with diabetes
and a history of sulfa-allergy, they might very well be better
served with acetalzolamide rather than glycerin (Osmoglyn)
since the latter packs a high calorie load which could exacerbate
their diabetes - even if only for a day or two. It seems
that the most critical factor in such decision-making would
be the degree of severity of the purported initial allergic
reaction. This same consideration should be valid when pondering
the use of a topical CAI glaucoma eyedrop, such as brinzolamide
or dorzolamide.
We are now more comfortable with the notion of using any of
the CAIs in patient giving a “soft” history of sulfa-allergy.
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