Hydroxychloroquine (Plaquenil) Dosing Calculator

Why Use

An appropriate dose is required to minimize the risk of hydroxychloroquine-related retinopathy and to permit long-term use in most patients. Risk increases with higher doses and long-term use. Calculation of appropriate dose of hydroxychloroquine can minimize the risk of hydroxychloroquine retinopathy, since vision loss is irreversible and there is no therapy to treat the resulting retinopathy.

When to Use

Use in an outpatient setting for adult patients taking hydroxychloroquine (Plaquenil).

Formula

Pearls / Pitfalls

The current American Academy of Ophthalmology (AAO) guidelines , published in 2016, recommend a maximum daily hydroxychloroquine dose of ≤5.0 mg/kg of actual body weight. These guidelines were established to minimize the likelihood of permanent vision loss related to hydroxychloroquine retinopathy. The 2016 revision was prompted by a study by Melles and Marmor in 2014, which suggested that hydroxychloroquine retinopathy is more common than previously thought. They demonstrated that a daily consumption of 5.0 mg/kg real body weight or less is associated with a low risk for up to 10 years. However, there is significant variability in individuals that develop hydroxychloroquine retinopathy. This study was performed only in adult patients. A 2020 Joint Statement by the American College of Rheumatology, American Academy of Dermatology, Rheumatologic Dermatology Society, and the American Academy of Ophthalmology supports the use of ≤5.0 mg/kg dosing. The American College of Rheumatology updated their guidelines in August 2016 to acknowledge the American Academy of Ophthalmology’s position, but it does not specify a preferred dosing regimen. Doses must be adjusted for renal insufficiency. Patients with underlying retinal or macular disease may be at a higher risk for toxicity. Patients who are undergoing tamoxifen therapy for breast cancer have a higher risk for toxicity.

Management

Doses should be adjusted in conjunction with the prescribing physician to minimize the risk of vision loss and to ensure that the medical risks of medication adjustment are managed. Recommended screening consists of automated visual fields (appropriate to race) and spectral-domain optical coherence tomography (SD-OCT). Other objective testing, such as a multifocal electroretinogram or fundus autofluorescence, should be performed as needed, if available. Ophthalmoscopy is not a recommended screening tool because photoreceptor damage can be detected by the above techniques before it becomes clinically visible.

Critical Actions

If a patient is on a dose that exceeds 5 mg/kg/day of actual body weight, the prescribing physician should be contacted to ensure that the dose can be adjusted and medical risks are managed.

More Information

Interpretation: Mean daily dose 10-year risk of retinopathy 20-year risk of retinopathy 4-5 mg/kg 2% 20% >5 mg/kg 10% 40%