OD News Articles

30th September 2003

Ocular Side Effects of Common Oral Meds

by Abigail Neal, OD Tacoma, WA

Perhaps Editor's notes here instead? Hydroxychloroquine (Plaquenil) Hydroxychloroquine is an anti-inflammatory drug that has been used in the treatment of rheumatoid arthritis and systemic lupus erythematosus since the 1950s. It suppresses the responsiveness of T lymphocytes to mitogens, interferes with the replication of viruses, decreases leukocyte chemotaxis, stabilizes lysosomal membranes, and traps free radicals.

Hydroxychloroquine (Plaquenil)

Hydroxychloroquineis an anti-inflammatory drug that has been used in the treatment of rheumatoid arthritis and systemic lupus erythematosus since the 1950s. It suppresses the responsiveness of T lymphocytes to mitogens, interferes with the replication of viruses, decreases leukocyte chemotaxis, stabilizes lysosomal membranes, and traps free radicals.

Symptoms of Toxicity include:

  • Blurred vision
  • Abnormal color vision
  • Poor dark adaptation

Signs of Toxicity include:

  • Bull’s eye ring of depigmentation surrounded by hyperpigmentation
  • Loss of foveal light reflex
  • Abnormal color vision
  • Central visual field abnormalities

Follow-up
Exams are recommended every 6 months. Specific testing should include:

  • Amsler grid
  • Color vision testing
  • Visual fields
  • Dilated fundus examination
  • Fundus photos
Prednisone

Prednisone is a corticosteroid used in treating autoimmune disorders, inflammatory bowel disease, lupus erythematosus, allergic reactions, asthma, COPD, and giant cell arteritis—among others. In general it is used to inhibit inflammation and to induce immunosupression.

Toxicity
Prednisone is quite cytotoxic to certain subsets of T cells but can suppress both cellular immunity and antibody as well as prostaglandin and leukotriene synthesis. Prednisone use may lead to cataract formation, pseudotumor cerebri, and elevated IOP. In most cases elevated IOP may occur during the first 4-6 weeks of use. Oral steroid use can lead to posterior subcapsular cataract and nuclear sclerosis after months to years of use.

Follow-up
IOP should be measured 2 months after initiation of treatment. Exams are recommended every 6-12 months thereafter. Specific testing should include:

  • Tonometry
  • Glare acuity
  • Dilated exam of lenses and fundus
Amiodarone (Cordarone)

Amiodarone is used to treat cardiac arrhythmias by delaying repolarization of the myocardium. It slows the sinus rate and atrioventricular conduction, prolongs the QT interval and QRS duration. It is a weak calcium channel blocker as well as a non-competitive beta-blocker. It also has anti-anginal effects.

Toxicity
Amiodarone is deposited in tissue and can be found in nearly every organ. Most readily it can be seen in the anterior subcapsular lens and cornea as yellowish-brown microcrystals. Such deposits usually occur after 1-3 months of use. Visual symptoms are rare with halos and reduction in acuity from the deposits occurring infrequently. Adverse neurologic effects however are common. Pseudotumor cerebri and optic neuropathy have been reported.

Follow-up

  • Exams are recommended every 6 to 12 months. Specific testing should include:
  • Slit lamp biomicroscopy
  • Amsler grid
  • Glare acuity
  • Dilated examination of lenses and fundus
Thioridazine (Mellaril)

Thioridazine is a phenothiazine derivative used for the management of schizophrenia. Phenothiozines have an affinity for binding to pigmented ocular surfaces like the retinal pigment epithelium.

Symptoms of Toxicity include:

  • Blurred vision
  • Brownish vision
  • Declining night vision

Signs of Toxicity include:

  • Pigment deposits in the equatorial retina
  • Retinal de-pigmentation
  • Corresponding visual field defects

Such changes appear to be dose dependent so thioridazine should be limited to 800mg per day to reduce the possibility of complications. It has been reported that phenothiazines also induce cataracts. It is suspected that the high lipophilicity of these drugs cause calcium to accumulate in the lens.

Follow-up

  • Exams are recommended every 6 months. Specific testing should include:
  • Amsler grid
  • Color vision testing
  • Glare acuity
  • Visual fields
  • Dilated examination of lenses and fundus
  • Fundus photos
Isoniazid (INH)

Isoniazid is an antitubercular drug which inhibits a variety of enzymes that are necessary for the survival of mycobacterium tuberculosis. By interfering with mycolic acid synthesis it disrupts the formation of the bacteria cell wall.

Toxicity
Symptoms of toxicity include blurred vision associated with its anticholinergic effects on the pupil and accommodation. At high dosing levels signs of RPE disruption may result in the macula. An uncommon but potentially serious side effect of isoniazid is optic neuropathy. It can occur in days to months from starting the drug. Isoniazid toxicity is variable in permanence. Discontinuation of the drug can allow for toxicity reversal if caught soon enough.

Follow-up

  • Exams are recommended every 3-6 months. Specific testing should include:
  • Amsler grid
  • Dilated fundoscopy
  • Visual field testing
Tamoxifen (Nolvadex)

Tamoxifen is a competitive inhibitor of estradiol at the receptor and is used in the treatment of breast cancer, and to reduce the risk of breast cancer in high risk women. It is used in doses of 10-20 mg twice daily. It has an initial half life of 7-14 hours and is predominantly excreted by the liver. Standard-term and long-term users of tamoxifen more frequently develop cataracts than non-users. One study shows that five or more years of tamoxifen use increases the risk of cataract.

Follow-up

  • Exams are recommended every 6-12 months, depending on duration of treatment. Specific testing should include:
  • Glare acuity
  • Dilated examination of lenses
References:

Basic and Clinical Pharmacology, Fifth Edition. Katzung BG. Appleton and langue 1992.

To T-QH and Townsend JC, Ocular toxicity of systemic medications: A Case Series. Optometry 2000;71:29-39.

Kamei A, Mizumoto Y, Takehana M. The relationship between properties of antipsychotic drugs and cataract formation. Biol Pharm Bull 1994 Feb;17(2):237-42.

Paganini-Hill a, Clark LJ. Eye Problems in breast cancer patients treated with tamoxifen. Breast Cancer Res Treat 2000 Mar;60(2):167-72.
 

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