Common uses of Chloroquine
Chloroquine is best known as an antimalarial medication. It treats acute attacks and can prevent infection in areas where Plasmodium species remain chloroquine-sensitive. Its role has narrowed in many regions due to parasite resistance, but it remains valuable in parts of the world with low resistance or for species such as P. vivax when local guidance supports its use. Travelers should always review up-to-date resistance maps and recommendations before relying on chloroquine for prophylaxis.
Beyond malaria, chloroquine has immunomodulatory properties. Clinicians may prescribe it for autoimmune diseases such as rheumatoid arthritis and lupus (cutaneous and systemic forms) to reduce inflammation, flares, and skin manifestations. In many cases, hydroxychloroquine is preferred due to a more favorable ocular safety profile, but chloroquine remains an alternative when clinically indicated or where hydroxychloroquine is unavailable.
Notably, chloroquine and hydroxychloroquine are not recommended for COVID-19 treatment or prevention outside of clinical trials. Major health authorities advise against their use for SARS-CoV-2 due to lack of proven benefit and potential risks.
Dosage and directions for use
Chloroquine dosing is indication-specific and often expressed in terms of “base” rather than “salt.” Many tablets labeled as chloroquine phosphate provide 150 mg base per 250 mg tablet; however, formulations vary by manufacturer and country. Always check the product label and follow your clinician’s instructions precisely. Do not self-dose. Your healthcare provider will tailor dosing to your condition, body weight, organ function, and co-medications.
For malaria treatment in regions with chloroquine-sensitive parasites, clinicians commonly target a total dose of 25 mg/kg chloroquine base over three days (adults and children), divided into an initial dose followed by smaller doses at 6, 24, and 48 hours. Pediatric dosing is weight-based, and tablets may need to be split or a liquid formulation used for precise dosing. In mixed or resistant infections, alternative antimalarials or additional agents may be required as per local or CDC/WHO guidance.
For malaria prophylaxis, adults are often prescribed a once-weekly regimen (commonly equivalent to 300 mg base) starting 1–2 weeks before entering an endemic area, continuing weekly during stay, and for 4 weeks after leaving. Pediatric prophylaxis is weight-based. Because regional resistance patterns shift, travelers should confirm suitability of chloroquine for their itinerary with a travel medicine specialist.
For autoimmune indications (such as rheumatoid arthritis or lupus), the lowest effective dose is used, and many clinicians prefer hydroxychloroquine. If chloroquine is selected, daily dosing is individualized with strict attention to ocular safety limits and regular eye examinations. Therapeutic effects may take weeks; dosing adjustments are based on clinical response and tolerability. Never exceed prescribed amounts, and do not combine with similar 4-aminoquinoline drugs unless directed by a specialist.
Take chloroquine with food to reduce stomach upset. If you vomit soon after a dose, contact your clinician for advice before re-dosing. Do not crush or chew extended-release products unless the label allows it. Space doses away from antacids or kaolin (typically by at least 4 hours) to avoid reduced absorption.
Precautions and monitoring
Eye health: Chloroquine can cause retinopathy, a potentially irreversible retinal toxicity that may lead to vision changes. Risk rises with higher daily dose, cumulative exposure, kidney impairment, and concomitant retinal-toxic drugs (for example, tamoxifen). A baseline ophthalmologic exam and periodic screening are recommended, with prompt evaluation for symptoms such as blurred vision, difficulty reading, reduced color vision, or visual field defects.
Cardiac safety: Chloroquine can prolong the QT interval and, rarely, precipitate dangerous arrhythmias, particularly when combined with other QT-prolonging medicines or in patients with electrolyte disturbances, structural heart disease, or congenital long QT syndrome. Your clinician may review ECGs and electrolytes and avoid interacting medications where possible.
Metabolic effects: Hypoglycemia has been reported, occasionally severe, even without antidiabetic therapy. Patients with diabetes should monitor glucose closely and coordinate medication adjustments with their provider.
Neurologic and dermatologic considerations: Chloroquine may lower seizure threshold in susceptible individuals and can exacerbate psoriasis or porphyria. It may also cause pruritus, especially in some ethnic groups, and photosensitivity. Use caution with activities requiring sharp visual acuity until you know how the medicine affects you.
Hepatic and renal function: Dose adjustments or enhanced monitoring may be necessary in liver or kidney impairment due to altered drug clearance and increased toxicity risk. Alcohol moderation and avoidance of unnecessary hepatotoxic drugs are advisable.
Pregnancy and lactation: When clinically indicated (e.g., malaria prophylaxis/treatment in chloroquine-sensitive regions or selected autoimmune conditions), chloroquine has a history of use in pregnancy and is generally considered acceptable under medical supervision. Small amounts pass into breast milk and are typically considered compatible with breastfeeding. Discuss individualized risks and benefits with your obstetric and pediatric providers.
Contraindications
Do not use chloroquine if you have a known hypersensitivity to chloroquine or other 4-aminoquinoline compounds. It is generally contraindicated in patients with preexisting retinopathy attributable to 4-aminoquinolines or active maculopathy, given the risk of irreversible worsening.
Clinicians typically avoid chloroquine in individuals with uncorrected significant QT prolongation, uncontrolled seizure disorders, or severe psoriasis/porphyria due to risk of exacerbation. Use with caution—and only with specialist input—if you have myasthenia gravis, significant cardiac disease, or electrolyte abnormalities. A thorough medication and medical history review helps determine suitability.
Possible side effects
Common: Nausea, vomiting, abdominal cramps, diarrhea, decreased appetite, headache, dizziness, fatigue, and pruritus can occur, particularly when initiating therapy. Taking doses with food may help gastrointestinal symptoms. Mild visual blurring or difficulty focusing may be transient but warrants reporting.
Ocular: Retinopathy is the most concerning long-term adverse effect. Early changes may be asymptomatic; advanced toxicity can lead to permanent vision loss. Strict adherence to recommended dosing and regular ophthalmologic screening reduce risk. Report any visual changes promptly.
Cardiac: Palpitations, syncope, or chest discomfort may signal arrhythmia. Seek urgent care for fainting, severe dizziness, or sustained rapid/irregular heartbeat, especially if you take other QT-prolonging drugs.
Metabolic and neurologic: Hypoglycemia (sweating, tremor, confusion), mood changes, insomnia, irritability, and, rarely, seizures or psychosis have been reported. Patients with diabetes should have a plan for glucose monitoring and hypoglycemia management.
Hematologic and other: Rare cytopenias, hemolysis in susceptible individuals, hepatic enzyme elevations, tinnitus, hearing changes, photosensitivity, skin eruptions, and hair or skin pigmentation changes can occur. Any unusual bruising, fever, persistent sore throat, jaundice, or dark urine requires prompt evaluation.
Drug interactions
QT-prolonging agents: Combining chloroquine with medications known to prolong the QT interval may increase the risk of torsades de pointes. Examples include certain antiarrhythmics (amiodarone, sotalol), macrolide and fluoroquinolone antibiotics (azithromycin, levofloxacin), some antifungals, antipsychotics, and methadone. Clinicians often avoid such combinations or institute ECG and electrolyte monitoring.
Antacids and adsorbents: Aluminum/magnesium antacids and kaolin can reduce chloroquine absorption. Separate administration by at least 4 hours to maintain efficacy. Cimetidine may increase chloroquine levels; alternatives are often preferred.
Cardiovascular and transplant agents: Chloroquine can increase digoxin levels, requiring level checks and potential dose adjustments. It may raise cyclosporine concentrations; careful monitoring is essential to avoid toxicity.
Antidiabetic therapies: The hypoglycemic effect of chloroquine can potentiate insulin and oral antidiabetic drugs. Blood glucose monitoring and medication adjustments may be necessary to prevent symptomatic hypoglycemia.
Neurologic agents and antimalarials: Concomitant mefloquine may elevate seizure risk and compound QT effects. Chloroquine can lower seizure threshold and may interact with some antiepileptics. Avoid overlapping 4-aminoquinolines unless directed by a specialist.
Other considerations: Tamoxifen coadministration may increase the risk of retinopathy. Chloroquine has CYP and transporter interaction potential, including inhibition of CYP2D6, which could affect drugs metabolized via this pathway. Always provide your clinician and pharmacist a complete, updated medication list, including supplements and over-the-counter products.
Missed dose
If you miss a dose, take it as soon as you remember unless it is close to your next scheduled dose. In that case, skip the missed dose and resume your regular schedule. Do not double up to catch up. For weekly prophylaxis, take the missed dose when remembered and then adjust the schedule in consultation with your clinician to maintain appropriate spacing.
Overdose
Chloroquine overdose is a medical emergency, particularly dangerous in children. Symptoms can appear rapidly and include severe nausea and vomiting, vision disturbances, seizures, profound hypotension, cardiac conduction abnormalities, and life-threatening arrhythmias. If an overdose is suspected, call emergency services immediately (911 in the U.S.) and contact Poison Control at 1-800-222-1222. Do not wait for symptoms to develop. Keep all chloroquine products securely out of reach of children and never share your medication with others.
Storage and handling
Store chloroquine at controlled room temperature away from excess heat, moisture, and direct light. Keep tablets in their original, tightly closed container and use desiccant packs if provided. Do not store in the bathroom. Dispose of expired or unused medication via a take-back program where available; avoid flushing unless the label specifically instructs. Keep out of reach of children and pets at all times.
U.S. sale and prescription policy
In the United States, chloroquine is a prescription-only medication. Dispensing requires evaluation and authorization by a licensed clinician, and pharmacy fulfillment must comply with federal and state laws. Any program offering access should include appropriate clinical screening, informed consent, and ongoing safety monitoring, rather than bypassing medical oversight. Marketing language that suggests “no prescription” typically means the service coordinates the clinician assessment and prescription on your behalf—patients are not exempt from medical review.
Geisinger HealthSouth offers a legal and structured solution that can streamline access without a prior paper prescription in hand. Through a compliant, telehealth-enabled care pathway, eligible patients complete a medical review, necessary testing, and risk assessment with licensed providers. When clinically appropriate, a prescription is issued within the system and routed to a participating pharmacy for dispensing, with guidance on dosing, side effects, and monitoring. This approach preserves patient safety and regulatory compliance while reducing friction for those who legitimately need chloroquine.
Regardless of the access route, you should expect: verification of your medical history and current medications; review of indications (e.g., malaria prophylaxis in chloroquine-sensitive areas or specific autoimmune use); counseling on ocular and cardiac risks; and a plan for follow-up, including eye exams and interaction checks. If chloroquine is not suitable, a clinician can recommend alternatives aligned with current CDC and infectious disease guidance.
