What monitoring is recommended for patients on hydroxychloroquine (HCQ)?

Hydroxychloroquine Monitoring Recommendations

Patients on hydroxychloroquine (HCQ) should receive baseline ocular examination at initiation of therapy and annual screening beginning after 5 years of use, with earlier screening for patients with risk factors. 1

Dosing Considerations

• Maximum recommended daily dose: ≤5 mg/kg of actual body weight 1
• At this dosage, risk of retinal toxicity is <2% for up to 10 years of use 1
• Higher doses significantly increase risk of retinopathy 2

Monitoring Schedule

Baseline Examination

• Perform within first year of HCQ initiation 1
• Purpose: rule out pre-existing maculopathy and establish reference point 1, 3
• Should include:
  • Best corrected distance visual acuity (BCVA)
  • Automated threshold visual field (VF) of central 10 degrees
  • Spectral domain optical coherence tomography (SD-OCT) 4

Ongoing Monitoring

• Annual screening should begin after 5 years of HCQ use 1
• Earlier and more frequent screening for patients with risk factors 1
• Annual screening should include:
  • Visual field testing (10-2 pattern for non-Asian patients; 24-2 or 30-2 for Asian patients) 1
  • At least one objective test: SD-OCT, multifocal electroretinogram (mfERG), or fundus autofluorescence (FAF) 1, 3

Risk Factors Requiring Earlier/More Frequent Screening

1. High daily dosage (>5.0 mg/kg actual body weight) 1, 2
2. Long duration of use (risk increases sharply after 10 years) 1, 2
3. Renal disease/impairment (increases systemic HCQ levels) 1, 4, 2
4. Concomitant tamoxifen use (increases risk 4.6 times) 1, 2
5. Pre-existing macular disease 1, 4
6. Asian ethnicity (different pattern of toxicity requiring wider field testing) 1
7. Low body weight (may lead to relative overdosing) 5
8. High myopia (associated with increased risk in Asian populations) 5

Pattern of Retinopathy

• Non-Asian patients: Typically parafoveal pattern of damage 1
• Asian patients: Often show extramacular pattern near the arcades 1
• Early detection is crucial as retinopathy can progress even after HCQ discontinuation 6

Clinical Pearls and Pitfalls

• Retinal toxicity is irreversible and no treatment exists 3
• Visual acuity usually remains excellent until advanced stages of toxicity 1
• Corneal deposits (verticillata) may occur but are not markers of retinal damage 1
• Amsler grid testing is no longer recommended for screening 3
• Visible bull's-eye maculopathy represents advanced disease; the goal is to detect toxicity before this stage 3
• Do not stop HCQ for uncertain findings; confirm with objective testing 1
• Even after 20 years of use, a patient without toxicity has only a 4% risk of developing it in the subsequent year 1

Monitoring for Other Toxicities

While retinal toxicity is the primary concern, other rare toxicities may require monitoring:

• Cardiac function (for cardiomyopathy and conduction disorders) 4
• Complete blood count (for rare hematologic effects) 1
• Electrolyte levels, particularly if risk factors for QT prolongation exist 4

By following these monitoring guidelines, clinicians can help minimize the risk of permanent vision loss while allowing patients to benefit from this valuable medication for managing autoimmune conditions.