Hydroxychloroquine

Drug Overview

Hydroxychloroquine is a medication with antiprotozoal activity and immunomodulatory effects, primarily used for treating autoimmune diseases and preventing malaria. Its chemical structure is similar to the antimalarial drug chloroquine, but it has lower toxicity and a better safety profile.

This drug works by suppressing excessive immune system activation and inhibiting the formation of antigen-antibody complexes, thereby alleviating symptoms of autoimmune diseases. In terms of antimalarial use, it can block the metabolic processes of Plasmodium within red blood cells.

Brand Names and Scientific Name

The scientific name is Hydroxychloroquine sulfate. Common brand names include Plaquenil®. In Taiwan and Hong Kong, this medication requires a prescription from a healthcare provider to obtain.

Drug Classification

It belongs to the 4-Aminoquinolines class of antimalarial drugs and is also categorized as an immunomodulator for autoimmune diseases.

Indications

Main indications: Used to relieve skin, joint, and systemic symptoms of systemic lupus erythematosus (SLE), as well as chronic inflammatory responses in rheumatoid arthritis.

Other uses: Also used for malaria prophylaxis and treatment (adjusted according to regional malaria prevalence), and in certain cases for connective tissue diseases such as dry eye syndrome or Sjögren’s syndrome.

Common Side Effects

• Mild side effects: Dry mouth, dizziness, mild diarrhea, skin pigmentation, which usually resolve after adaptation.
• Gastrointestinal discomfort: May cause nausea and abdominal pain; taking with food is recommended to reduce gastrointestinal symptoms.

• Serious side effects:
  • Retinal toxicity: Long-term use may lead to blurred vision or retinal degeneration; regular ophthalmologic examinations are necessary.
  • Electrocardiogram abnormalities: May prolong the QT interval, increasing the risk of arrhythmias; special caution is needed for patients with heart disease.
• Rare allergic reactions: Such as urticaria or difficulty breathing; immediate discontinuation and medical attention are required.

Warnings and Precautions

Contraindications: Patients allergic to 4-Aminoquinolines should avoid use. Patients with severe hepatic or renal impairment, retinal disease, or cardiac conduction abnormalities should not use this medication.

Pregnancy and Lactation: Use cautiously during early pregnancy, with an assessment of risks to the mother and fetus. During breastfeeding, the drug may be secreted into breast milk; a healthcare provider should evaluate whether to discontinue medication or breastfeeding.

Drug Interactions

Concurrent use with Class I antiarrhythmic drugs (e.g., quinidine) may cause fatal arrhythmias, requiring strict ECG monitoring. Combining with certain antibiotics (such as macrolides or fluoroquinolones) or antifungal medications may increase cardiac toxicity.

When used with immunosuppressants (e.g., corticosteroids), monitoring for immunosuppression-related complications is necessary. Using certain potassium-sparing diuretics simultaneously may increase the risk of hypokalemia.

Dosage and Administration

For autoimmune diseases: Adults typically take 100-400 mg daily, divided into 1-2 doses, with dosage adjusted based on symptoms. For malaria prophylaxis, a weekly single dose is used.

Tablets should be swallowed whole and not chewed, preferably with food to reduce gastrointestinal discomfort. Patients with chronic conditions should undergo regular blood tests to monitor liver and kidney function and visual health.

Missed Dose Management

If a dose is missed within 1 hour, take it immediately; if close to the next scheduled dose, skip the missed dose. Do not take a double dose to make up for a missed one.

Overdose Management

Overdose may cause seizures, arrhythmias, or permanent retinal damage. Immediate medical attention is required, including gastric lavage or activated charcoal adsorption therapy.

During emergency treatment, ECG monitoring and blood drug concentration assessments are necessary. Severe cases may require antiarrhythmic drugs or dialysis.

 

Frequently Asked Questions

Does hydroxychloroquine need to be taken with food? What are the effects of taking it on an empty stomach?

It is recommended to take hydroxychloroquine with meals or immediately after eating to reduce gastrointestinal discomfort. Taking on an empty stomach may cause nausea, diarrhea, and other gastrointestinal reactions. If severe discomfort occurs, contact a healthcare provider to adjust the medication regimen.

Can long-term use of hydroxychloroquine cause vision problems? How should I monitor this?

Long-term use of hydroxychloroquine may affect retinal health. Regular ophthalmologic examinations every 3 to 6 months, including visual acuity tests and retinal imaging, are advised. If symptoms such as blurred vision or color discrimination issues occur, discontinue the medication and seek medical evaluation immediately.

Does hydroxychloroquine interact with other antipruritic drugs (such as antihistamines)?

Combining hydroxychloroquine with antihistamines may increase the risk of arrhythmias, especially QT prolongation. Inform your healthcare provider of all medications being taken to avoid unassessed drug interactions.

Can I receive vaccinations while taking hydroxychloroquine?

Vaccination during treatment is generally safe, but hydroxychloroquine may reduce the immune response to certain vaccines. Live vaccines (such as measles or varicella) should be administered with caution, and it is best to confirm vaccine types and timing with your healthcare provider before vaccination.

Should I taper off hydroxychloroquine gradually or stop suddenly? What are the effects of abrupt discontinuation?

The need for tapering depends on the indication and disease course. For autoimmune diseases, gradual dose reduction under medical supervision is recommended to prevent symptom rebound. Abrupt discontinuation may lead to disease exacerbation and should not be decided independently.