Hydroxychloroquine: Uses, Mechanism of Action and Contraindications

What is Hydroxychloroquine?

Hydroxychloroquine is a blood schizonticidal drug. It is classified as anti-malarial medication and is used in the treatment of malaria, rheumatoid arthritis, and systemic lupus erythematosus (SLE). It is also classified as a disease-modifying anti-rheumatic drug (DMARD). Hydroxychloroquine is also prescribed to prevent malaria in travelers to those countries where malaria is endemic. In the case of malaria treatment, the drug is only effective when malaria is uncomplicated.

Mechanism of Action of Hydroxyquinoline

Chloroquine and hydroxychloroquine raise the pH of intracellular vacuoles, affecting activities such as protein degradation by acidic hydrolases in the lysosome, protein post-translation modification in the Golgi apparatus, macromolecule assembly in endosomes. It binds to heme (preventing its polymerization to hemozoin which is non-toxic for the parasite) and increases the pH which eventually results in oxidative damage to the membranes.

This process leads to the death of the parasite as well as RBCs. When it comes to the drug’s anti-malarial activity, these two particulars i.e. binding of the drug to heme and prevention of its polymerization into parasite-friendly substance (hemozoin) have a central role.

The secretion of cytokines such as interleukin-1 and tumor necrosis factor is also reduced by hydroxychloroquine. It’s suggested that the anti-rheumatic properties of the drug hydroxychloroquine and chloroquine are attributed to interference with “antigen processing” in antigen-presenting cells and macrophages.

Pharmacokinetics of Hydroxychloroquine

It shows 67-74% bioavailability. It shows plasma protein binding up to 50%. CYP3A4 N-dealkylates hydroxychloroquine to produce the active metabolite desethylhydroxychloroquine and the inactive metabolites desethylchloroquine and bidesethylchloroquine. The drug is eliminated from the body through urine, feces, and skin.

How to take Hydroxychloroquine?

It is advised to be taken with food or milk.

Who should not take Hydroxychloroquine?

Patients suffering from psoriasis should avoid taking hydroxychloroquine.

Who can take Hydroxychloroquine?

  • Children of all ages
  • Adults
  • Pregnant women

Is it safe in pregnancy?

The use of hydroxychloroquine is generally considered safe during pregnancy. If you’re thinking about starting a family or if you become pregnant while taking it, talk to your doctor as soon as possible.

Can lactating mothers take hydroxychloroquine?

If you’re using Hydroxychloroquine, you can still breastfeed. Even though the drug may enter into breast milk, it is unlikely to have any effect on the baby. The advantages of continuing to take it when you’re pregnant or breastfeeding, the advantages usually exceed the risks.


Where to Buy?

Antimalarial medications are only available by prescription in the United States. Medicines should be purchased before traveling rather than in the target country. Purchasing pharmaceuticals from a foreign country carries risks: the drugs may be of poor quality, contaminated, or counterfeit, and may not protect the individual from malaria.

Hydroxychloroquine Side Effects

Common side effects associated with the use of hydroxychloroquine include

  • Nausea
  • Abdominal pain
  • Headache
  • Dizziness
  • Nervousness
  • Sensory-motor disorders
  • Pigmentation
  • Urticarial
  • Hypoglycemia
  • Anemia
  • Bone marrow depression
  • Diarrhea
  • Vomiting
  • Retinal toxicity

In case of ocular effects, the drug should be immediately discontinued.

Hydroxychloroquine Drug Interactions

It shows interaction with the following drugs:

  • Amiodarone
  • Digoxin
  • Moxifloxacin
  • Antacids
  • Ciclosporin
  • Tamoxifen
  • Antidiabetic drugs
  • Acebutolol
  • Acetaminophen
  • Acetazolamide

How to take Hydroxychloroquine?

The drug is typically given twice a day. Each pill contains 200 milligrams. The normal dosage is one or two pills per day. This medicine should be used on a daily basis at the same time. It will take one to two months to get up and running. Follow your doctor’s advice. Take only the amount of medicine prescribed. It’s best to take this drug with food or milk. It is critical that your doctors know if you are taking any other medications while taking Hydroxychloroquine. Prescription and over-the-counter medications, as well as birth control pills, vitamins, and herbal supplements are all included.

Can I take it for covid prevention?

According to WHO, data of clinical trials upon prevention of Covid-19 by hydroxychloroquine suggests that the drug has little or no effect on illness or death.

Hydroxychloroquine Henry Ford study

Henry Ford’s COVID-19 hydroxychloroquine trial was secretly stopped off after a while. In spring 2020, when erstwhile US President Trump pitched it as a potential game-changer, in the prevention and treatment of the then newly emerged coronavirus, it sparked some interest. However, early excitement gave way to larger medical research, with the country’s top health agencies eventually concluding that it was ineffective in treating or stopping the spread of the new coronavirus. The trials were ended before Christmas 2020. Henry Ford announced the termination of the hydroxychloroquine project by stating that from now on, vaccines will be their primary objective of protecting their frontline healthcare workers.

How to take Hydroxychloroquine sulfate?

Take this drug by mouth as advised by your doctor, typically with food to avoid stomach problems. The dosage and duration of medication are determined by your medical condition and treatment response. Dosage is individualized as per body weight in children.

Can you take it with milk?

Yes. Hydroxychloroquine can be taken with milk or food.

Can it cause liver demage?

Metabolized in the liver, hydroxychloroquine can affect the way other drugs are processed. Therapy is unlikely to induce liver damage in healthy people, but it can cause an abrupt aggravation of porphyria cutanea tarda in a vulnerable population.

Hydroxychloroquine Indication

It is used to treat the following conditions:

  • Erythrocytic Plasmodium falciparum malaria
  • Plasmodium vivax malaria
  • Systemic lupus erythematosus (SLE)
  • Acute rheumatoid arthritis
  • Chronic discoid lupus erythematosus
  • Chronic rheumatoid arthritis
  • Porphyria cutanea tarda

Who makes it?

Name of some of the major manufacturers of hydroxychloroquine are

  • Sanofi
  • Pfizer
  • Novartis

Popular Brands of Hydroxychloroquine

  • Plaquenil


Hydroxychloroquine (Plaquenil®) Drug Information Sheet

Lippincott’s illustrated reviews Pharmacology 4th edition


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