Aralen is a brand-name medication that contains chloroquine phosphate as its active ingredient. It is classified as an antiparasitic drug and is primarily prescribed for the prevention and treatment of malaria. In Hong Kong, Aralen is a prescription-only (Rx) product regulated by the Pharmacy and Poisons Board of the Department of Health. The medication is supplied in pill form and is available in strengths of 250 mg and 500 mg.
Chloroquine belongs to the 4-aminoquinoline class of antimalarials. After oral ingestion, the drug is well absorbed and distributes widely into tissues, including the liver, spleen, and melanin-containing cells of the eye. Within the malaria parasite, chloroquine accumulates in the acidic food-vacule where it interferes with heme polymerization. The parasite normally detoxifies free heme by converting it into inert hemozoin; chloroquine blocks this conversion, causing toxic build-up of heme that kills the parasite.
The same pharmacologic property-interference with intracellular acidification-has been observed in laboratory studies of certain viruses, which sparked interest in chloroquine as a potential COVID-19 therapy. However, the clinical relevance of this antiviral mechanism has not been confirmed in robust human trials.
Aralen is approved for prophylactic use in travelers to regions where malaria is endemic. The typical regimen involves a weekly dose of 500 mg (one 500 mg tablet) taken starting 1-2 weeks before travel, continuing throughout the stay, and for 4 weeks after leaving the endemic area.
For the treatment of acute, uncomplicated malaria caused by chloroquine-sensitive Plasmodium species, a common schedule includes:
These dosing patterns reflect standard clinical practice and are consistent with the strengths available for Aralen.
In some jurisdictions chloroquine is prescribed for autoimmune conditions such as rheumatoid arthritis and systemic lupus erythematosus. This article focuses on the malaria indications that are officially approved in Hong Kong.
Early in the 2020 COVID-19 pandemic, chloroquine phosphate was investigated as an off-label treatment because laboratory studies showed the drug could inhibit SARS-CoV-2 replication in cell culture. Large, well-controlled clinical trials later demonstrated no significant clinical benefit and raised concerns about cardiac toxicity, particularly QT-interval prolongation. Consequently, the Hong Kong Department of Health, mirroring international regulators such as the U.S. FDA and the European EMA, does not approve chloroquine for COVID-19.
Disclaimer: Off-label use of chloroquine for COVID-19 should only occur under close medical supervision, with baseline and follow-up cardiac monitoring, and after a thorough risk-benefit assessment.
Symptoms may include severe nausea, vomiting, visual disturbances, cardiac arrhythmias, or seizures. Seek emergency medical attention immediately. Treatment is largely supportive; there is no specific antidote.
For prophylactic use, stop the weekly dose after the recommended post-travel period. For treatment courses, completion of the prescribed three-day regimen is essential. Abrupt cessation does not typically cause withdrawal, but patients should inform their prescriber of any adverse reactions that may require an alternative therapy.
This article provides educational information about Aralen (chloroquine phosphate) and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
Concurrent use of multiple antimalarials is generally unnecessary and may increase the risk of toxicity. If combination therapy is considered (e.g., for multidrug-resistant malaria), it should be prescribed and monitored by an infectious disease specialist.
Report any new visual symptoms-such as blurred vision, seeing halos, or difficulty focusing-to a healthcare professional promptly. An ophthalmologic exam is required to assess for early retinopathy.
Yes, continuing the weekly dose during travel to non-endemic areas maintains steady drug levels and can be stopped after the recommended post-travel period without increased risk.
Authentic Araren tablets are round, film-coated, and bear the imprint “AR” on one side and the dosage strength (250 mg or 500 mg) on the other. Obtain medication from licensed pharmacies to avoid counterfeit products.
St. John’s Wort induces CYP enzymes that could lower chloroquine concentrations, potentially reducing efficacy. Discuss all herbal products with a prescriber before starting Araren.
A ketogenic diet does not directly affect chloroquine metabolism, but any major dietary change should be discussed with a healthcare provider to ensure overall medication safety.
Chloroquine is not listed as a prohibited substance by major sporting agencies. However, athletes should disclose all medications to the relevant anti-doping authority.
The 500 mg tablet is typically medium-blue, film-coated, and imprinted with “AR-500”. The 250 mg tablet is smaller, white, and bears the imprint “AR-250”.
Yes, several manufacturers supply generic chloroquine phosphate tablets in the same strengths (250 mg and 500 mg). Both brand-name Araren and generics must meet the same quality standards set by the Pharmacy and Poisons Board.
