HCQ is a relatively common drug used in the treatment of rheumatoid arthritis, systemic and discoid lupus erythematosus and various dermatological conditions that are aggravated by sunlight [BNF]. The dose is typically 200mg to 400mg on a daily basis, with the maximum dose based on patient body weight [BNF]. The general advice is for annual monitoring in all patients who have taken HCQ for longer than 5 years (i.e. due to bioaccumulation of the drug, especially with low eGFR). This is very important counselling information to provide to patients in the Community Pharmacy space, for example.
HCQ can cause irreversible sight loss. A recognised side effect of HCQ is called 'Bullseye Maculopathy', which is demonstrated in the images below. In the field of Ophthalmology, the aim of monitoring for HCQ retinopathy is to detect the earliest definitive signs. Early signs are detected using methods such as optical coherent tomography and wide field fundus autofluorescence. If detected early, those patients affected can readily seek alternative medications in consultation with their prescribing clinician. This is useful advice that the Community Pharmacist can provide. This confirms the need for effective healthcare professional communication to support cohesive patient care.
Key risk factors for ‘Bullseye Maculopathy’ include:
• Concomitant Tamoxifen use
• Impaired renal function eGFR < 60 ml/min/1.73m2
• HCQ dose > 5mg/kg per day
• Chloroquine use
• Duration of HCQ use
Should you be interested, statistics / research on this topic include:
• A UK-based audit of a population monitored according to RCOphth 2018 monitoring criteria identified a prevalence of HCQ retinopathy as 6.3% in patients taking the drug for 5 yrs or more [1].
• A large US study showed patients with a mean daily use exceeding 5.0 mg/kg had approximately a 10% risk of retinal toxicity within 10 years of treatment and an almost 40% risk after 20 years [2].
References
1. Marshall E, Robertson M, Kam S, Penwarden A, Riga P, Davies N. Prevalence of hydroxychloroquine retinopathy using 2018 Royal College of Ophthalmologists diagnostic criteria. Eye (London, England). 2020:1-6.
2. Melles RB, Marmor MF. The risk of toxic retinopathy in patients on long-term hydroxychloroquine therapy. JAMA ophthalmology. 2014;132(12):1453-60.
Autofluorescence of the retina showing normal vs bullseye with HCQ