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Plaquenil (Hydroxychloroquine) Information

Plaquenil (hydroxychloroquine sulphate) is an essential oral medication belonging to the 4-aminoquinoline class of compounds. Originally developed as an antimalarial agent, it is now classified as a Disease-Modifying Anti-Rheumatic Drug (DMARD) due to its potent anti-inflammatory and immunomodulatory properties. Plaquenil is primarily indicated for the treatment of autoimmune diseases, specifically Systemic Lupus Erythematosus (SLE) and Chronic Discoid Lupus Erythematosus. It is also a widely used treatment for acute and chronic Rheumatoid Arthritis (RA). Furthermore, it remains indicated for the prophylaxis and treatment of uncomplicated malaria in areas where the Plasmodium species are sensitive to chloroquine.

Unlike fast-acting immunomodulators, Plaquenil's therapeutic action is cumulative. It has a characteristically slow onset, often requiring several weeks to months to achieve maximum beneficial effects in chronic autoimmune conditions. Long-term compliance is critical, as some patients may need to use it for several years or even their entire lives to control disease activity. Dosage for autoimmune conditions must not exceed a calculated daily dose of 5.0 milligrams per kilogram of ideal body weight (of the salt form), as exceeding this threshold sharply increases the risk of severe toxicity, particularly irreversible retinal damage.

The precise mechanism of action for hydroxychloroquine in autoimmune diseases is complex and not fully elucidated. However, it centers on modulating the immune response. It is known to be a weak base that accumulates in acidic intracellular compartments, such as endosomes and lysosomes, of various cells, including antigen-presenting cells (APCs). By increasing the pH within these vesicles, hydroxychloroquine is thought to disrupt several key processes:

• Interference with Antigen Processing: It impairs the degradation of antigenic proteins and the assembly of their peptides with Major Histocompatibility Complex (MHC) class II proteins. This action effectively reduces the presentation of autoantigens to T-cells, thereby down-regulating the overall autoimmune inflammatory response.

• Toll-Like Receptor (TLR) Suppression: It suppresses the activation of endosomal TLRs, which play a significant role in innate immunity and autoimmune disease pathology, particularly in lupus. By binding to nucleic acids in the activation pathway, it blunts the production of pro-inflammatory cytokines like interferon-alpha.

Plaquenil Side Effects

Hydroxychloroquine is generally well-tolerated in comparison to many other DMARDs. Common side effects often involve the gastrointestinal system, including nausea, vomiting, abdominal cramps, and diarrhea, which can frequently be mitigated by taking the drug with food or milk. Other minor side effects include headache, dizziness, hair loss, and changes in hair colour. However, treatment with Plaquenil carries a risk of serious and potentially irreversible side effects, which necessitate careful patient selection and continuous monitoring. The medication carries a Boxed Warning for the risk of fatal overdose, especially in children, and for the risk of irreversible retinopathy. If any of the following symptoms are experienced, the patient should stop taking the medication and seek immediate medical attention:

• Blood Dyscrasias: Rare reports of severe blood disorders, including aplastic anemia, agranulocytosis, and thrombocytopenia, suggest a need for periodic blood counts in patients on prolonged therapy.

• Cardiomyopathy and Ventricular Arrhythmias: Post-marketing reports include rare cases of life-threatening and fatal cardiomyopathy and conduction disorders (e.g., atrioventricular block, bundle branch block). Plaquenil can also prolong the QT interval, potentially leading to a risk of Torsades de Pointes and sudden cardiac arrest.

• Neuropsychiatric Events / Suicidality: Rare reports of serious mood and mental changes, including suicidal thoughts and behaviour, warrant caution in patients with a history of mental health issues.

• Proximal Myopathy and Neuropathy: Skeletal muscle weakness, reduced deep tendon reflexes, and atrophy, which may necessitate drug discontinuation.

• Retinal Toxicity / Irreversible Maculopathy (Boxed Warning): The most serious ocular risk, which can lead to permanent vision loss, is characterized by visual field changes or pigmentary alterations in the retina (maculopathy). A baseline comprehensive ophthalmologic examination is mandatory, and periodic (often annual) re-examination is typically required after five years of use for most patients. Risk factors include high daily doses, cumulative dose, and underlying renal impairment.

• Severe Hypoglycemia: Plaquenil can cause profound hypoglycemia (low blood sugar), including loss of consciousness, in patients with or without concurrent anti-diabetic medications.

Plaquenil Precautions

A detailed discussion of medical history is necessary before initiating hydroxychloroquine therapy, especially given the Boxed Warning regarding the risk of fatal overdose in children, for whom the drug must be stored securely and away from reach. Plaquenil is contraindicated in patients with pre-existing retinopathy or known hypersensitivity to 4-aminoquinoline compounds. The maximum recommended daily dosage of 5.0 milligrams of the salt per kilogram of ideal body weight must never be exceeded, as this dramatically elevates the risk of retinal toxicity. Due to the high risk of cardiotoxicity, it must be used with extreme caution in patients with pre-existing cardiac conditions (e.g., heart failure, prolonged QT interval, or arrhythmia history) and in those with uncorrected hypokalemia or hypomagnesemia. Caution and potential dose reduction are necessary in patients with significant hepatic or renal impairment, as these conditions can increase drug accumulation and toxicity. The drug should also be used cautiously in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, as it may cause hemolysis. Plaquenil can exacerbate pre-existing conditions like psoriasis and porphyria, and its use in these settings requires a careful risk-benefit analysis. Concurrent use with other medications that prolong the QT interval (e.g., amiodarone, certain antipsychotics) or are known to be arrhythmogenic must be carefully considered and monitored due to the compounded cardiac risk.

Do I need a prescription to order Plaquenil?

Yes, a prescription is required from your physician to order Plaquenil.