From the Guidelines
Plaquenil (hydroxychloroquine) is considered an immunomodulatory medication rather than a traditional immunosuppressant, as it has anti-inflammatory and immunomodulatory effects without significantly suppressing the immune system. It works by interfering with the communication between immune cells and reducing the production of certain inflammatory chemicals in the body 1. Plaquenil was originally developed as an antimalarial drug but is now commonly prescribed for autoimmune conditions like rheumatoid arthritis, lupus, and certain inflammatory disorders.
The benefits of hydroxychloroquine use in patients with systemic lupus erythematosus (SLE) include lower flare rates, higher response rates to therapy, and less organ damage, as reported in the 2024 KDIGO clinical practice guideline for the management of lupus nephritis 1. The recommended starting dose of hydroxychloroquine is around 5 mg/kg/d, and doses of 2–3 mg/kg/d may not achieve adequate blood levels and could be associated with higher flare rates 1.
Some key points to consider when prescribing Plaquenil include:
- Regular monitoring is important while on this medication, particularly eye examinations every 6-12 months, as prolonged use can rarely cause retinal damage 1.
- Common side effects include nausea, headache, and dizziness, which often improve with continued use.
- Hydroxychloroquine may accumulate in lysosomes and cause a form of phospholipidosis with accumulation of multilamellar zebra bodies in podocytes that can mimic the appearance of Fabry disease 1.
- The potential benefits of preventing organ damage and vascular complications were judged as being important to patients, and the relatively low risk of adverse events associated with hydroxychloroquine would also be important to patients 1.
In terms of dosage and administration, the 2019 update of the EULAR recommendations for the management of systemic lupus erythematosus suggests that hydroxychloroquine should be used at a dose not exceeding 5 mg/kg real body weight 2. Overall, the use of Plaquenil as an immunomodulatory medication can be beneficial in reducing autoimmune disease activity while maintaining normal activities, but regular monitoring and careful consideration of potential side effects are necessary.
From the FDA Drug Label
The mechanisms underlying the anti-inflammatory and immunomodulatory effects of hydroxychloroquine sulfate in the treatment of rheumatoid arthritis, chronic discoid lupus erythematosus and systemic lupus erythematosus are not fully known.
Hydroxychloroquine is not explicitly stated as an immune suppressant in the provided drug labels. However, it does have immunomodulatory effects, which means it can modify or regulate the immune system.
- The exact mechanisms of these effects are not fully understood.
- It is used to treat conditions like rheumatoid arthritis and systemic lupus erythematosus, which are autoimmune diseases.
- The drug labels do not provide direct information on whether hydroxychloroquine is an immune suppressant 3.
From the Research
Definition and Mechanism of Action
- Hydroxychloroquine (HCQ), also known by its trade name Plaquenil, is an antimalarial drug that has been used to treat several diseases, including rheumatic autoimmune disorders and COVID-19 4, 5, 6, 7, 8.
- HCQ affects various cellular and molecular pathways through different mechanisms, including inhibiting lysosomal antigen processing, MHC-II antigen presentation, and TLR functions 4, 7.
Immune System Effects
- HCQ has immunomodulatory and anti-inflammatory effects, which alter several aspects of the immune system, reducing pro-inflammatory cytokine production and release 4, 6, 7.
- HCQ reduces the need for glucocorticoids and immunosuppressants and increases their effectiveness in treating rheumatic diseases 6.
Therapeutic Uses
- HCQ is used to treat rheumatic autoimmune disorders, such as systemic lupus erythematosus, primary Sjögren's syndrome, and rheumatoid arthritis 4, 5, 6, 7.
- HCQ has also been used to treat other diseases, including malaria, dermatologic diseases, oncologic diseases, multiple sclerosis, diabetes, cardiovascular diseases, and recurrent miscarriages 6.
Safety and Efficacy
- HCQ is generally considered safe, but adverse reactions have been reported, including cardiac, neuropsychiatric, hematologic, and hepatobiliary manifestations 5, 7, 8.
- The efficacy and safety of HCQ in treating COVID-19 are still uncertain, and its use is not recommended outside clinical trials under strict medical supervision 7, 8.