Chloroquine (Chloroquine Phosphate) — Patient Information (UK)

Chloroquine (often supplied as chloroquine phosphate) is a medicine used mainly for certain malarial infections and, in some situations, for specific inflammatory conditions under clinical supervision. This page explains how it works, how it is taken, what to expect, and key safety information for people in the United Kingdom.

Medicines information can vary by individual circumstances and local guidance. Always follow the advice provided by your healthcare professional and read the medicine’s patient information leaflet (PIL) supplied with your product.

Basic product information

How chloroquine works (mechanism of action)

Chloroquine’s main known action is against the malaria parasite Plasmodium. It interferes with the parasite’s ability to break down haemoglobin, which the parasite uses for survival. Inside infected red blood cells, chloroquine concentrates in acidic compartments of the parasite. There it raises the pH and prevents the formation of haeme detoxification products. As a result, toxic substances build up and the parasite is damaged.

For some inflammatory or immune-related conditions, chloroquine is thought to affect cellular processes, including lysosomal activity and immune signalling, helping to reduce inflammation.

Pharmacokinetics: what the body does to chloroquine

Pharmacokinetics describes how the body absorbs, distributes, metabolises, and eliminates a medicine. Chloroquine is absorbed after oral administration and is widely distributed throughout the body. It can accumulate in tissues and has a relatively long duration of action.

• Absorption: Typically absorbed from the gastrointestinal tract after swallowing tablets.
• Distribution: Widely distributed; it can accumulate in organs and tissues.
• Metabolism: Metabolised in the body (mainly via liver pathways).
• Elimination: Excretion occurs through renal and non-renal routes.
• Half-life: Can be long, meaning effects and side effects may last beyond the final dose.

Because chloroquine can persist in the body, it is important not to miss doses if you are taking it for malaria, and to take care with monitoring if taking it longer term for other conditions.

Typical uses in the UK

In the UK, chloroquine is most commonly discussed in relation to malaria prevention/treatment in settings where it remains appropriate, depending on local resistance patterns and travel advice. It may also be used in selected inflammatory conditions where it is considered suitable by clinicians.

Important note: Malaria treatment recommendations change over time based on resistance. Always check the most up-to-date advice for the region you are travelling to and follow clinician guidance for the right regimen.

Possible indications

• Malaria: Treatment of Plasmodium species where chloroquine is effective (subject to susceptibility/resistance).
• Inflammatory/immune conditions: Used for selected cases such as certain forms of rheumatoid arthritis, lupus and other conditions where appropriate monitoring is available.

Dosing and timing

Dosing depends on the reason for taking chloroquine, the infecting species (for malaria), your age, and other health factors. For malaria, dosing schedules may vary by local guidance and product strength. For inflammatory conditions, doses are often started carefully and reviewed over time.

Your healthcare professional will calculate the correct schedule for you. Do not adjust the dose yourself.

General principles for timing

• Take at the same time(s) each day if you are on a multi-day course.
• For longer-term use, regular dosing schedules are important to maintain benefit and reduce risk of toxicity through consistent monitoring.
• If you miss a dose: follow the guidance in the PIL. If unsure, consult your pharmacist or healthcare professional.

Taking chloroquine with food

Food effects can vary between people and products, but generally:

• Taking with food may help reduce stomach upset and improve tolerance.
• If your medicine’s leaflet recommends with or after food, follow that advice.
• Do not take extra doses to “catch up” unless advised.

If you experience nausea, taking the tablet with a meal (or immediately after eating) can often make it easier to continue.

Alcohol interactions

There is no universally guaranteed “safe” amount of alcohol while taking chloroquine. Alcohol may:

• Increase stomach irritation and worsen nausea or dizziness.
• Increase strain on the liver (especially relevant if you have liver disease or are on multiple medications).
• Complicate monitoring if you feel unwell or if symptoms overlap (e.g., dizziness, fatigue).

In practice, it is sensible to avoid or limit alcohol during treatment and seek advice if you plan to drink.

Medicine interactions (important)

Chloroquine can interact with other medicines, which may increase side effects or reduce effectiveness. Tell your pharmacist/clinician about all medicines you take, including over-the-counter products and herbal supplements.

Common interaction areas

• Heart rhythm medicines (QT-prolonging drugs): Some medicines can affect electrical activity in the heart. Using them with chloroquine may increase the risk of abnormal rhythm. Examples include certain antiarrhythmics, some antipsychotics, and some antibiotics/antifungals known to affect QT.
• Seizure/neurological medicines: Interactions may affect seizure threshold or neurological side effects.
• Diabetes medicines: Chloroquine can affect blood sugar levels in some people. Monitoring may be needed if you take insulin or oral diabetes medicines.
• Medicines affecting blood counts: Rare blood-related side effects may be more likely if combined with other drugs that also affect blood cells.
• Other antimalarials: May alter effectiveness and side-effect risk when used together.

Practical interaction advice

• Keep a list of your medicines and show it to your pharmacist.
• If you feel palpitations, faintness, or severe dizziness, seek urgent help.
• Do not start a new medicine (including OTC) without checking compatibility.

Safety profile: side effects and when to seek help

Like all medicines, chloroquine can cause side effects. Many people tolerate it well, but some adverse effects can be serious. The risk can depend on dose, duration, age, and other health conditions.

Common side effects

• Nausea and/or vomiting
• Headache
• Diarrhoea or abdominal discomfort
• Dizziness
• Loss of appetite

Serious side effects (seek medical help promptly)

• Eye/vision changes: Blurred vision, difficulty focusing, or changes in colour vision. This risk increases with longer use. New vision symptoms should be assessed urgently.
• Heart rhythm problems: Fast, irregular heartbeat, fainting, or severe dizziness. This can be life-threatening.
• Severe allergic reaction: Rash with swelling, breathing difficulty, or collapse.
• Severe skin reactions: Widespread rash, blistering, or peeling skin.
• Unusual bleeding or infection signs: Unexplained bruising, persistent fever, sore throat, or marked fatigue.

Risk factors to discuss with a clinician

• Existing heart rhythm conditions or a history of QT prolongation
• Liver or kidney impairment
• Long-term use (increases eye/retina risk)
• Older age or frailty
• Concomitant medicines that affect the heart, vision, or blood counts

Practical use tips (making treatment easier and safer)

• Take with food if you get nausea.
• Don’t double up if you miss a dose unless your instructions say so.
• Stay hydrated, especially if you’re ill (e.g., with malaria symptoms) or experiencing diarrhoea/vomiting.
• Monitor symptoms: track fever, pain, breathing, and any new visual changes.
• Eye monitoring (for longer-term use): clinicians may arrange baseline and periodic eye checks (including visual acuity and, where appropriate, retinal screening).
• Heart awareness: if you feel palpitations or faintness, stop taking and seek urgent advice (unless your clinician has already provided a specific plan).

For any persistent or worsening symptoms, contact a healthcare professional promptly.

Alternative options

Alternatives depend on the condition being treated and—if it is malaria—on the region and parasite susceptibility. In the UK, clinicians base choices on current travel and treatment guidance.

Malaria-related alternatives

• Other antimalarials (choice depends on resistance patterns and the species involved).
• Combination regimens may be recommended in areas where chloroquine resistance is common.

Inflammatory/immune condition alternatives

• Other disease-modifying medicines used for rheumatoid arthritis or lupus (such as hydroxychloroquine, depending on suitability and monitoring requirements).
• Immunosuppressive therapies may be considered in more severe or refractory cases.

If you are switching medicines, do this with clinical advice. Stopping chloroquine suddenly (especially when used long-term for inflammatory conditions) may worsen symptoms.

UK market and legal context (overview)

In the United Kingdom, availability and prescribing practices for chloroquine can be influenced by:

• Licensed indications and product-specific authorisations
• Local clinical guidelines for malaria prevention and treatment
• Regulatory requirements for safe supply, labelling, and patient information
• Demand and stock availability, which can affect delivery timelines

For travel-related malaria, UK guidance is also informed by up-to-date surveillance of resistance patterns and public health recommendations. Where resistance is present, alternative medicines are often preferred.

If you are looking to obtain chloroquine in the UK, ensure your product is from a reputable supplier and includes a current PIL and correct batch/expiry information.

Recent guidance and how it may affect use

Recommendations for malaria prevention and treatment can change frequently. Guidance may be updated due to:

• Local changes in drug resistance
• New clinical evidence on effectiveness and safety
• Public health updates for travellers

If you are using chloroquine for travel or malaria treatment, check whether the medicine remains appropriate for your destination and time frame. A clinician or travel clinic can confirm the best option for your itinerary.

Delivery and availability in the UK

Availability may vary depending on local pharmacy supply, the product strength, and stock levels. When ordering online, delivery times can also depend on whether the medicine is dispatched from a local or distribution hub.

• Dispatch: Often within 1–2 working days, depending on stock.
• Delivery: Commonly within 1–3 working days after dispatch (service level varies by supplier).
• Stock status: If out of stock, restocking dates may be shown at checkout.

Always ensure the packaging is intact and that the product has a valid expiry date.

Frequently Asked Questions (FAQ)

1) What is chloroquine phosphate used for?

Chloroquine phosphate is used primarily for malaria in situations where chloroquine is suitable based on parasite susceptibility. It may also be used for certain inflammatory/immune conditions under clinical supervision, with monitoring for side effects.

2) How should I take chloroquine?

Take it exactly as directed for your condition. Many people find that taking it with food reduces nausea. Use the same timing pattern each day if it is a multi-dose course.

3) Can I take chloroquine with food?

Usually, yes. Food may improve tolerability. Follow the instructions in your medicine leaflet for whether it should be taken with or after food.

4) What should I do if I miss a dose?

Refer to the patient leaflet for your specific product, as instructions differ. If you are unsure, contact a pharmacist for advice rather than guessing or doubling the dose.

5) Are there foods I must avoid?

There are no universally required dietary restrictions, but maintaining regular meals and hydration can help reduce stomach upset. If you are also taking other medicines, check for their food advice too.

6) Can I drink alcohol while taking chloroquine?

It’s best to avoid or limit alcohol during treatment, as alcohol may worsen side effects and increase strain on the body. Ask a pharmacist if you want personalised advice.

7) What interactions are most important?

Medicines that can affect the heart rhythm (QT), and medicines for seizures or diabetes may be particularly relevant. Provide your pharmacist with a full list of medicines and supplements.

8) What are warning signs I should not ignore?

Seek medical help promptly if you develop vision changes, fainting or palpitations, signs of severe allergy (swelling/breathing trouble), or severe skin reactions.

9) Does chloroquine affect eyesight?

It can, especially with longer-term use. That is why eye monitoring is often recommended when used beyond short courses. Report any new blurred vision or colour/visual changes quickly.

10) How long does chloroquine stay in the body?

Chloroquine can persist for some time due to a relatively long duration of action. This is one reason monitoring and caution may be needed even after finishing treatment.

11) Who should be extra careful?

People with heart rhythm issues, significant liver or kidney impairment, older adults, and those taking medicines that may interact with chloroquine should discuss suitability and risk with a healthcare professional.

12) What are common alternatives?

Alternatives depend on the condition. For malaria, other antimalarials may be preferred depending on resistance. For inflammatory conditions, other medications (including hydroxychloroquine in some cases) may be considered along with monitoring plans.

Summary

Chloroquine (chloroquine phosphate) is an antimalarial medicine that works by disrupting the parasite’s ability to process haemoglobin. It also has roles in some inflammatory conditions, depending on suitability. Because chloroquine can affect the heart rhythm and may cause eye-related side effects (particularly with longer use), safe use relies on correct dosing, awareness of interactions, and appropriate monitoring.

If you have questions about whether chloroquine is appropriate for your situation—especially for travel or malaria—consult a healthcare professional and check the latest UK guidance and advice for your destination.