Hydroxychloroquine
Hydroxychloroquine (HCQ) has been used since the 1950s to treat rheumatic diseases like rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). It's less effective than other immunosuppressive or biologic therapies for RA, but is commonly used in combination regimens or as monotherapy for milder SLE.
Pharmacology
HCQ is orally absorbed (~70%), with a slow clearance from the body, taking about 3 months to reach steady-state concentrations. It is excreted mostly by renal clearance, it has a half-life of around 40 days and can interact with drugs like digoxin and beta-blockers.
Mode of Action
nitially believed to affect phagosomal and lysosomal function, HCQ now appears to work by inhibiting intracellular TLRs, especially TLR9, impacting SLE, RA, diabetes, and hyperlipidemia. It reduces IFN-ฮฑ levels, which are significant in SLE pathogenesis, and has potential benefits in antiphospholipid syndrome.
Efficacy
- RA: Shows moderate efficacy as monotherapy and is often used in combination with other DMARDs.
- SLE: Proven effective for joint and cutaneous manifestations and preventing disease flares.
- Metabolic Effects: May benefit cardiovascular disease, diabetes, and dyslipidemia patients due to its effects on lipid and glucose metabolism.
Toxicity
It is generally safe, but can cause gastrointestinal, skin, and ocular side effects. It can cause ocular toxicity, including retinopathy, is rare but can progress to irreversible damage. Risk increases with long-term use. It requires careful monitoring, especially after 5 years of use.
Dosing
It is generally dosed at maximum 5 mg/kg per day. So usually the dose is somewhere between 200-400mg based on weight.
This summary should give you a comprehensive overview of the key aspects of HCQ in the treatment of RA and SLE, its pharmacological properties, mode of action, efficacy, safety profile, and dosing recommendations.
