Hydroxychloroquine (HCQ) : Uses, Dosage, Side Effects, Interactions, & Contraindications

Hydroxychloroquine (HCQ) : Therapeutic uses, Clinical uses, Indications, Dosage, Side Effects, Warnings, Interactions, Precautions, Contraindications & Brand names

Hydroxychloroquine sulfate (HCQ) is a quinoline drug, useful in treating malaria, certain autoimmune diseases like rheumatoid arthritis, lupus erythematosus.

Dose : 200-800 mg [200 mg salt = 155 mg HCQ base]
Route : Oral
Onset of action : ?
Plasma half-life : 30-60 days (~40 days)
Duration of action : N/A
Bioavailability : Incomplete & variable (~70%)
Plasma protein binding : 40%
Metabolism : Hepatic (Metabolites include bidesethylchloroquine, desethylHCQ, desethylchloroquine)
Pregnancy risk category : NA
Chemical formula : C18H26ClN3O
IUPAC name : (RS)-2-[{4-[(7-chloroquinolin-4-yl)amino]pentyl}(ethyl)amino]ethanol
Trade name : Plaquenil, Quineprox, Hydroquin, Axemal, Dolquine, Quensyl, Quinoric, Zhquine, ZyQ
Therapeutic uses : Hydroxychloroquine sulfate has following usage :

  • Used to prevent & treat the uncomplicated malaria due to susceptible strains.
  • Used to treat certain auto-immune diseases (lupus, rheumatoid arthritis).
  • Off Label Uses: Coronavirus Disease 2019 (COVID-19), Dermatomyositis, Photosensitivity diseases – porphyria cutanea tarda & severe polymorphous light eruption, Primary Sjögren syndrome, Q fever, Sarcoidosis.

Is hydroxychloroquine effective for COVID-19?

Few studies find hydroxychloroquine is not effective for COVID-19 and few studies find it is. Hence, more trials are needed before we will know for sure if hydroxychloroquine is effective for COVID-19.

Mechanism of action 


  • Hydroxychloroquine interfere with heme detoxification.

Hydroxychloroquine, a weak base, concentrates in the highly acidic digestive vacuoles of susceptible Plasmodium, where it binds to heme and disrupts its sequestration.

Inhibiting polymerization of heme

Failure to inactivate heme or even enhanced toxicity of drug-heme complexes is thought to kill the parasites via oxidative damage to membranes, digestive proteases, or other critical biomolecules.

Autoimmune diseases

  • Exact mechanism unknown but may include inhibition of phospholipase A2 and platelet aggregation, membrane stabilization, effects on the immune system, and antioxidant activity.

Coronavirus Disease 2019 (COVID-19)

  • Hampers low PH dependant steps of viral replication.

Side effects : Hydroxychloroquine is safe when taken in proper doses and for recommended total durations. Commonly observed side effects are as following:


  • GI upset such as nausea, vomiting, loss of appetite, diarrhea,
  • Dizziness, or headache,
  • Urticaria, Pruritus.


  • Blurring of vision, diplopia,
  • Confusion, convulsions,
  • Lichenoid skin eruptions, bleaching of hair,
  • Widening of the QRS interval (QTc prolongation), T-wave abnormalities,
  • Hemolysis and blood dyscrasias particularly in G6PD,
  • Discoloration of nail beds & mucous membranes,
  • Retinopathy (dose-dependent),
  • Ototoxicity.

Acute toxicity: HCQ acute toxicity is encountered most frequently when therapeutic or high doses are administered too rapidly because its safety margin is narrow.

  • Toxic manifestations: Cardiovascular effects (include hypotension, vasodilation, suppressed myocardial function, cardiac arrhythmias, and eventual cardiac arrest), CNS effects (include confusion, convulsions, & coma).
  • Treament: Prompt treatment with mechanical ventilation, epinephrine, and diazepam.

Patients receiving long-term, high-dose therapy should undergo ophthalmological and neurological evaluations every 3-6 months.

Drug Interactions : Hydroxychloroquine may interact with following drugs :

  • Mefloquine × HCQ : Increased risk for QTc-prolongation & seizures, lack of added benefit.
  • QT-prolonging Agents × HCQ : Enhancing the QTc-prolonging effect of QT-prolonging Agents (Highest Risk).
  • Digoxin × HCQ : Increases the serum concentration of digoxin.
  • Cyclosporine × HCQ : Increases the serum concentration of digoxin.
  • Antidiabetic Agents × HCQ : May enhance the hypoglycemic effect of Hypoglycemia-Associated Agents.
  • Yellow fever vaccine × HCQ: Attenuates the efficacy of vaccine when administered at the same time.
  • Antiepileptics × HCQ : Activity of antiepileptic drugs might be impaired.
  • Penicillamine × HCQ


Before using this medication, tell your doctor or pharmacist

  • If you are allergic to it; or if you have any other allergies.
  • Your medical history, especially of G6PD deficiency, eye problems, ear problems, kidney disease, liver disease, regular alcohol use/abuse, skin problems such as psoriasis, blood disorders such as porphyria, seizures, myasthenia gravis.


  • HCQ should be used cautiously if at all in the presence of advanced liver disease or severe GI, neurological, or blood disorders.
  • In individuals with decreased renal function, dosage should be adjusted to avoid elevated plasma concentrations.
  • HCQ is not recommended for treating individuals who have epilepsy or myasthenia gravis.
  • Concomitant use of gold or phenylbutazone with HCQ, in the treatment of rheumatoid arthritis, should be avoided because of the tendency of all three agents to produce dermatitis.
  • HCQ should not be prescribed for patients with psoriasis or other exfoliative skin conditions because it can cause severe reactions.
  • Because of the danger of cutaneous reactions, it should also not be used to treat malaria in patients with porphyria cutanea tarda; however it can be used in lower doses for treatment of manifestations of this form of porphyria.


  • Known hypersensitivity to hydroxychloroquine, 4-aminoquinoline derivatives, or any component of the formulation.
  • Preexisting retinopathy.
  • Children <6 years or weighing <35 kg.

For detailed query or in case of uncertainty, Always consult your doctor or pharmacist.

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