Both neostigmine and pyridostigmine antagonize the action of hydroxychloroquine.While there may be a link between hydroxychloroquine and hemolytic anemia in those with glucose-6-phosphate dehydrogenase deficiency, this risk may be low in those of African descent.Specifically, the US Food and Drug Administrations (FDA) drug label for hydroxychloroquine lists the following drug interactions:
Digoxin (wherein it may result in increased serum digoxin levels)
Insulin or anti-diabetic medication (wherein it may enhance the effects of a hypoglycemic treatment)
Drugs that prolong QT interval and other arrhythmogenic drugs (as Hydroxychloroquine prolongs the QT interval and may increase the risk of inducing serious abnormal heart rhythms (ventricular arrhythmias) if used concurrently)
Mefloquine and other drugs known to lower the seizure threshold (co-administration with other antimalarials known to lower the convulsion threshold may increase risk of convulsions)
Antiepileptics (concurrent use may impair the antiepileptic activity)
Methotrexate (combined use is unstudied and may increase the frequency of side effects)
Cyclosporin (wherein an increased plasma cyclosporin level was reported when used together). Pharmacology
Pharmacokinetics
Hydroxychloroquine has similar pharmacokinetics to chloroquine, with rapid gastrointestinal absorption, large distribution volume, and elimination by the kidneys. Cytochrome P450 enzymes (CYP2D6, 2C8, 3A4 and 3A5) metabolize hydroxychloroquine to N-desethylhydroxychloroquine. Both agents also inhibit CYP2D6 activity and may interact with other medications that depend on this enzyme. Pharmacodynamics
Antimalarials are lipophilic weak bases and easily pass plasma membranes. The free base form accumulates in lysosomes (acidic cytoplasmic vesicles) and is then protonated, resulting in concentrations within lysosomes up to 1000 times higher than in culture media. This increases the pH of the lysosome from four to six.
Hydroxychloroquine, sold under the brand name Plaquenil among others, is a medication used to prevent and treat malaria in areas where malaria remains sensitive to chloroquine. Other uses include treatment of rheumatoid arthritis, lupus, and porphyria cutanea tarda. It is taken by mouth, often in the form of hydroxychloroquine sulfate.Common side effects may include vomiting, headache, changes in vision, and muscle weakness. Severe side effects may include allergic reactions, vision problems, and heart problems. Although all risk cannot be excluded, it remains a treatment for rheumatic disease during pregnancy. Hydroxychloroquine is in the antimalarial and 4-aminoquinoline families of medication.Hydroxychloroquine was approved for medical use in the United States in 1955. It is on the World Health Organizations List of Essential Medicines. In 2019, it was the 122nd most commonly prescribed medication in the United States, with more than 5 million prescriptions.Hydroxychloroquine has been studied for an ability to prevent and treat coronavirus disease 2019 (COVID-19), but clinical trials found it ineffective for this purpose and a possible risk of dangerous side effects. Among studies that deemed hydroxychloroquine intake to cause harmful side effects, a publication by The Lancet was retracted due to data flaws. The speculative use of hydroxychloroquine for COVID-19 threatens its availability for people with established indications. Medical uses
Hydroxychloroquine treats rheumatic disorders such as systemic lupus erythematosus, rheumatoid arthritis, and porphyria cutanea tarda, and certain infections such as Q fever and certain types of malaria. It is considered the first-line treatment for systemic lupus erythematosus.