indication

For the suppressive treatment and treatment of acute attacks of malaria due to Plasmodium vivax, P. malariae, P. ovale, and susceptible strains of P. falciparum. It is also indicated for the treatment of discoid and systemic lupus erythematosus, and rheumatoid arthritis.

pharmacology

Hydroxychloroquine possesses antimalarial properties and also exerts a beneficial effect in lupus erythematosus (chronic discoid or systemic) and acute or chronic rheumatoid arthritis. The precise mechanism of action is not known.

mechanism of action

Although the exact mechanism of action is unknown, it may be based on ability of hydroxychloroquine to bind to and alter DNA. Hydroxychloroquine has also has been found to be taken up into the acidic food vacuoles of the parasite in the erythrocyte. This increases the pH of the acid vesicles, interfering with vesicle functions and possibly inhibiting phospholipid metabolism. In suppressive treatment, hydroxychloroquine inhibits the erythrocytic stage of development of plasmodia. In acute attacks of malaria, it interrupts erythrocytic schizogony of the parasite. Its ability to concentrate in parasitized erythrocytes may account for their selective toxicity against the erythrocytic stages of plasmodial infection. As an antirheumatic, hydroxychloroquine is thought to act as a mild immunosuppressant, inhibiting the production of rheumatoid factor and acute phase reactants. It also accumulates in white blood cells, stabilizing lysosomal membranes and inhibiting the activity of many enzymes, including collagenase and the proteases that cause cartilage breakdown.

toxicity

Symptoms of overdose include headache, drowsiness, visual disturbances, cardiovascular collapse, and convulsions, followed by sudden and early respiratory and cardiac arrest. The electrocardiogram may reveal atrial standstill, nodal rhythm, prolonged intraventricular conduction time, and progressive bradycardia leading to ventricular fibrillation and/or arrest.

biotransformation

Partially hepatic, to active de-ethylated metabolites.

absorption

Very rapidly and completely absorbed following oral administration.

half life

Terminal elimination half-life In blood is approximately 50 days. In plasma it is approximately 32 days.

drug interactions

Artemether: Hydroxychloroquine may increase the adverse effects of artemether. Combination therapy is contraindicated unless there are no other treatment options.

Digoxin: Hydroxychloroquine increases the effect of digoxin

Lumefantrine: Hydroxychloroquine may increase the adverse effects of lumefantrine. Combination therapy is contraindicated unless there are no other treatment options.

Methotrexate: Hydroxychloroquine increases the effect and toxicity of methotrexate