From the Guidelines
Plaquenil (hydroxychloroquine) is primarily used to treat several autoimmune conditions, including rheumatoid arthritis, systemic lupus erythematosus (SLE), and other inflammatory rheumatic diseases, as well as certain types of malaria. The medication is also effective for treating discoid lupus erythematosus, juvenile idiopathic arthritis, and certain skin conditions caused by lupus. According to the 2019 update of the EULAR recommendations for the management of systemic lupus erythematosus 1, hydroxychloroquine is recommended for all patients with SLE due to its multiple beneficial effects. Additionally, hydroxychloroquine is used for preventing and treating certain types of malaria, though it is not effective against all strains, as noted in the 2024 guidelines for managing adult patients with malaria in non-endemic settings 1. The typical adult dosage ranges from 200-400 mg daily, often taken with food to reduce stomach upset. The medication works by reducing inflammation in autoimmune conditions, though its exact mechanism isn't fully understood, and is believed to interfere with the communication between immune cells and decrease the production of inflammatory chemicals in the body, as described in the 2020 article on urgent guidance for navigating and circumventing the QTc-prolonging and torsadogenic potential of possible pharmacotherapies for COVID-19 1. For malaria, it works by preventing the parasite from breaking down hemoglobin. Patients should be aware that Plaquenil requires regular eye exams due to rare but serious potential retinal toxicity, especially with long-term use or higher doses. Some key points to consider when prescribing Plaquenil include:
- Monitoring for retinal toxicity, especially in patients with a history of eye problems or those taking high doses of the medication
- Adjusting the dosage based on the patient's weight and kidney function
- Avoiding concomitant use with other medications that may increase the risk of retinal toxicity or other adverse effects
- Educating patients on the importance of regular eye exams and the potential risks and benefits of Plaquenil treatment. It's also important to note that hydroxychloroquine has been studied as a potential treatment for COVID-19, although its effectiveness for this indication is still being researched, as mentioned in the 2020 article on recommendations for coronavirus infection in rheumatic diseases treated with biologic therapy 1. Overall, Plaquenil is a valuable medication for the treatment of various autoimmune conditions and certain types of malaria, but its use requires careful consideration of the potential risks and benefits, as well as regular monitoring for adverse effects.
From the FDA Drug Label
Hydroxychloroquine sulfate tablets are an antimalarial and antirheumatic indicated for the: Treatment of uncomplicated malaria due to Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, and Plasmodium vivax in adult and pediatric patients. Prophylaxis of malaria in geographic areas where chloroquine resistance is not reported in adult and pediatric patients. Treatment of rheumatoid arthritis in adults. Treatment of systemic lupus erythematosus in adults. Treatment of chronic discoid lupus erythematosus in adults.
Plaquenil (hydroxychloroquine) treats:
- Uncomplicated malaria due to Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, and Plasmodium vivax
- Rheumatoid arthritis in adults
- Systemic lupus erythematosus in adults
- Chronic discoid lupus erythematosus in adults
- It is also used for the prophylaxis of malaria in geographic areas where chloroquine resistance is not reported 2
From the Research
Conditions Treated by Plaquenil (Hydroxychloroquine)
Plaquenil, also known as hydroxychloroquine, is used to treat various conditions, including:
- Systemic lupus erythematosus (SLE) 3, 4, 5
- Rheumatoid arthritis (RA) 3, 4, 6
- Malaria 7
- Sjøgren's syndrome 4
- Osteoarthritis (OA) 4
- Phospholipid antibody (aPL) syndrome 3
- COVID-19 (although its use is not recommended due to the risk of adverse events outweighing potential benefits) 7
Mechanism of Action
The exact mechanism of action of hydroxychloroquine is not fully understood, but it is believed to:
- Interfere with antigen processing in macrophages and other antigen-presenting cells 6
- Increase pH within intracellular vacuoles and alter processes such as protein degradation and assembly of macromolecules 6
- Diminish the formation of peptide-MHC protein complexes required to stimulate CD4+ T cells and result in down-regulation of the immune response against autoantigenic peptides 6
Benefits and Risks
Hydroxychloroquine has been shown to:
- Reduce serum lipid levels, including cholesterol, triglycerides, and low-density lipoproteins 3
- Prevent thrombosis in patients with phospholipid antibody (aPL) syndrome 3
- Improve glycaemia and reduce the risks of type II diabetes mellitus 4
- However, it can also cause adverse events, including cardiac, neuropsychiatric, hematologic, and hepatobiliary manifestations, particularly when used to treat COVID-19 7