Conventional DMARDs · Pain & inflammation
Hydroxychloroquine
HCQ · Plaquenil®(brand names vary by market)
The gentlest DMARD, with a toxicity that only shows up in the eye.
Mechanism
Accumulates in lysosomes and raises their pH, impairing antigen processing and Toll-like receptor signalling. The mechanism is slow, which is why the clinical effect takes months.
Indications
- Systemic lupus erythematosus, where it is foundational
- Rheumatoid arthritis
- Sjögren syndrome
- Malaria prophylaxis and treatment
Formulations
Dosing concepts
Weight-based ceiling
Retinopathy risk relates to dose per kilogram of actual body weight and to cumulative duration, so the dose is capped rather than titrated upward for effect.
Onset
Three to six months to full effect. Judging it at six weeks is judging it too early.
Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.
Pharmacokinetics
- Bioavailability
- ~75%
- Half-life
- ~40 days
- Elimination
- mixed: Renal and hepatic; the very long half-life means both onset and offset take months
- Protein binding
- ~45%
Adverse effects
- Gastrointestinal upsetcommon
- RetinopathyseriousDose- and duration-related, initially asymptomatic, and irreversible once established. This is the reason for screening.
- Skin hyperpigmentationcommon
- Cardiomyopathy and QT prolongationseriousRare with long-term use.
- Hemolysis in G6PD deficiencyserious
Contraindications & precautions
Contraindications
- Pre-existing retinopathy from this class
Precautions
- Renal or hepatic impairment
- G6PD deficiency
- Concurrent QT-prolonging drugs
- Long duration of therapy
Interactions
No curated interaction entries yet for this agent.
Monitoring
Baseline retinal examination, then annual screening after five years of use
Retinopathy is asymptomatic until it is irreversible · Baseline, then annually from year 5, earlier with risk factors
Disease activity
Efficacy, judged over months
Renal function and weight
They set the safe dose
Counselling points
- It takes several months to work. Keep taking it.
- You will need an eye check before starting and then regularly; this is important even though your vision feels fine.
- Take it with food to reduce stomach upset.
- It is safe to continue in pregnancy, which is unusual in this class.
Clinical pearls
- It is one of the few immunomodulators continued through pregnancy, and stopping it in lupus increases flare and adverse pregnancy outcomes. Reflexively stopping 'all the drugs' in a pregnant lupus patient causes harm.
- Retinal screening is scheduled by cumulative exposure rather than by symptoms, because by the time vision changes the damage cannot be undone.
References & review
- Hydroxychloroquine product monograph (consult the current version for your market) (monograph)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)
Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.