Plaquenil Toxicity
Plaquenil is prescribed by the physician for several medical conditions. Patients who take these medications are at risk for toxicity [1, 2].
What is Plaquenil?
Plaquenil or hydroxychloroquine is under the quinolone family. These medications are initially used in the prophylaxis and treatment of malaria. Plaquenil has replaced chloroquine because it produces less retinal side effects. Aside from its initial intended use, it has been also used for the management of rheumatoid arthritis, systemic lupus erythematosus and several other connective tissue disorders [1]. Although it is considered rare, retinal toxicity from the intake of Plaquenil can be irreversible even if the drug is discontinued [2, 3].
What is Plaquenil Toxicity?
The toxicity resulting from the intake of Plaquenil is due to its affinity for melanin-containing structures in the body. With prolonged usage, metabolites in the drug accumulate in the retina. The drug remains in these parts even if the patients stopped taking the drugs. Studies have shown that patients who have manifested with retinopathy have traces of Plaquenil metabolites in their erythrocytes, plasma, and urine even after 5 years of discontinuing the medication [1, 2, 3].
Risk Factors
There are risk factors which may increase the likelihood of an individual in developing symptoms of Plaquenil toxicity [1].
Dosage
The amount of drug the patient takes play a big role in increasing the risk for toxicity. Any daily dose of greater than 400 mg and being prescribed a maintenance dose of more than 6.5 mg/kg/day may increase the likelihood [1].
Duration of treatment
Taking Plaquenil for more than 5 years and if the total amount taken by the patient reaches more than 1000 g may put the patient at risk for the toxicity [1].
Patient characteristics
The characteristics of patients which may increase of developing toxicity symptoms while taking Plaquenil include an age of more than 60 years old, having renal or hepatic insufficiency or any existing macular degeneration and retinal disease [1].
Signs and Symptoms
Patients who are in the earlier stages of the toxicity may not notice any symptoms although there are rare reports of paracentral scotoma which causes a problem in reading and diminished color vision. The patient may not be able to notice this change and will cause for the symptom to progress. If it is not addressed timely, it may lead to problems with visual acuity, night vision, and peripheral vision. Upon physical examination, there is a bilateral change in the retinal pigment that may give the appearance of a bulls-eye [2, 3].
Treatment
If the patient manifests the toxicity symptoms of Plaquenil, the standard of care is to stop taking the medication and to change the medication the patient is taking. Possible coordination with the dermatologist or the rheumatologist may be required for the continuous care.
Ammonium chloride may be given for serious sensitivity or overdosage. It may be given 3-4 times per week for several weeks after the intake of Plaquenil. Acidification of the urine may also improve the urinary excretion of the drug [1, 2, 3].
Prevention
The best way to prevent the occurrence of Plaquenil toxicity is to monitor the patient annually on the duration of the therapy. Annual monitoring should include an examination of the visual acuity and fundus examination. The physician should note any visual symptoms as well. After 5 years of therapy, an ocular examination, 10-2 threshold field testing and any one objective testing is recommended [1, 4].
Taking Plaquenil should be combined with monitoring for any visual problem. You can share any additional information that you may have in the comment box below.
References
- Roque, M. R. (2015, November 3). Chloroquine and Hydroxychloroquine Toxicity. Retrieved from Medscape: http://emedicine.medscape.com/article/1229016-overview?pa=bgYcm8CKzJaJoxmtVATTLjYtxGsRNPmBU3pjDZx482FsYDgFGzPR8VTFjdfKBgGXYiiWSa2T1BNtIkaVsLtpCF%2FDMAtBBAsM6eN9kpLn%2Fas%3D#a3
- Hansen, M. S., & Schuman, S. G. (2011, June). Hydroxychloroquine-Induced Retinal Toxicity. Retrieved from American Academy of Ophthalmology: https://www.aao.org/eyenet/article/hydroxychloroquine-induced-retinal-toxicity
- Drugs.com. (2012, November 13). Plaquenil Side Effects. Retrieved from Drugs.com: https://www.drugs.com/plaquenil.html
- Chen, J. J., Tarantola, R. M., Kay, C. M., & Mahajan, V. B. (2011, August 30). Hydroxychloroquine (Plaquenil) Toxicity and Recommendations for Screening. Retrieved from University of Iowa Health Care: http://webeye.ophth.uiowa.edu/eyeforum/cases/139-plaquenil-toxicity.htm
Similar Posts:
- Gentamicin Toxicity
- Tacrolimus Toxicity
- Coumadin Toxicity
- Liver Toxicity
- Fluoroquinolone Toxicity
- Mercury Toxicity
- Fluoride Toxicity
- Digoxin Toxicity
- Phenytoin Toxicity
- Niacin Toxicity