According to the US National Center for Health Statistics, the most common therapeutic intervention performed by physicians is prescribing medications.
Ocular Side Effects
of Prescription Medications
INTRODUCTION
According
to the US National Center for Health Statistics, the most common therapeutic
intervention performed by physicians is prescribing medications. In
ophthalmology, adverse events caused by prescription medications are the third
most common reason for lawsuits against the doctor (Easterbrook, 1999; Edwards
and Biriell, 1995). Litigation from drug-related ocular side effects can be
costly to defend, indemnify and settle due to the serious and sometimes
long-term effects of vision loss.
Many
prescription and non-prescription drugs, homeopathic agents, herbal medicines,
chemicals and toxins are associated with ocular toxicity. Adverse effects on
the eye are one of the most common reasons why drugs do not reach the
marketplace. Although the liver and kidneys are the most common sites for drug
toxicity, large areas of these organs may be damaged before laboratory findings
appear abnormal. However, if an adverse drug reaction affects the macula of the
eye, even a small fraction of patients (1%) may show significant abnormality on
testing.
Drug-induced
adverse ocular effects are caused by topical medications, including their
preservatives and by systemic medications. Drugs (especially antimetabolites)
may concentrate in the tears, caus-ing marked irritation and even scarring of
the mucous membrane overlying the eye. Dilation of the pupil by atropine and
similar agents can cause acute glaucoma; oral and topical corticosteroids can
cause open-angle glaucoma by depositing mucopolysaccharides in the ocular
outflow channels. Lens opacification caused by steroids or allopurinol and
disruption of the pigmented tissue of the macula by chloroquine or
hydroxychloro-quine are not uncommon.
The
key to detecting an adverse ocular effect is a high degree of clinical
suspicion and the recog-nition that the signs and symptoms of a disease do not
fit the expected clinical picture. The busy clini-cian can easily overlook a
drug-related ocular adverse event, especially if patients are taking multiple
topi-cal or systemic medications. It is estimated that the incidence of adverse
events from topical ocular medi-cations alone is 13% (Wilson, 1983). How best
to determine whether a drug-related adverse event has occurred is shown in
Table 36.1. The World Health Organization (WHO) has defined these events, as
summarized in Table 36.2 (WHO 1972; Edwards and Biriell, 1995).
With
more than 30 000 prescription drugs in the United States alone and many more
worldwide, plus a multitude of over-the-counter and herbal prod-ucts available,
it is impossible to cover the subject entirely in this short chapter. Probably
the two most comprehensive textbooks are Grant and Schuman’s Toxicology of the Eye (1993) and
Fraunfelder and Fraunfelder’s Drug-Induced Ocular Side Effects (2001).
The National Registry of Drug-Induced Ocular Side Effects is also a source of help to the busy clini-cian (www.eyedrugregistry.com). The objectives of the registry are
• to establish a national center where possible
drug-induced ocular side effects can be accumulated,
• to add to this database the spontaneous
reports of possible drug-induced ocular side effects collected by the Food and
Drug Administration (FDA) (Rockville, MD, USA) and the WHO (Uppsala, Sweden),
• to compile data from the world literature on
possi-ble drug-induced side effects in humans,
• to publish this data every 4–5 years in book
form and
• to make this data available to physicians who
suspect possible drug-induced ocular side effects.
Clinicians
may contact the database for help with a suspected drug reaction, to access
data in the registry, or to report a case. When sending data, it would be ideal
to include name of drug, dosage, duration of therapy, suspected reaction, what
happened if the drug was stopped or rechallenged, concomitant drugs and the
name and address of person reporting the case (optional but encouraged).
Reports
can be mailed to
National
Registry of Drug-Induced Ocular Side Effects
Casey
Eye Institute
3375
SW Terwilliger Blvd. Portland, OR 97239-4197, USA
or
faxed: (503) 494-4286
or
e-mailed: www.eyedrugregistry.com
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