Hydroxychloroquine

Absorption

Hydroxychloroquine is 67-74% bioavailable. Bioavailability of the R and S enantiomers were not significantly different.
Following a single 200 mg oral dose of hydroxychloroquine to healthy male volunteers, whole blood hydroxychloroquine Cmax was 129.6 ng/mL (plasma Cmax was 50.3 ng/mL) with Tmax of 3.3 hours (plasma Tmax 3.7 hours). Following a single oral hydroxychloroquine dose of 200 mg, the mean fraction of the dose absorbed was 0.74 (compared to the administration of 155 mg of hydroxychloroquine intravenous infusion). Peak blood concentrations of metabolites were observed at the same time as peak levels of hydroxychloroquine.
After administration of single 155 mg and 310 mg intravenous doses, peak blood concentrations ranged from 1161 ng/mL to 2436 ng/mL (mean 1918 ng/mL) following the 155 mg infusion and 6 months following the 310 mg infusion. Pharmacokinetic parameters were not significantly different over the therapeutic dose range of 155 mg and 310 mg indicating linear kinetics.
In patients with rheumatoid arthritis, there was large variability as to the fraction of the dose absorbed (i.e. 30 to 100%), and mean hydroxychloroquine levels were significantly higher in patients with less disease activity.

Toxicity

Patients experiencing an overdose may present with headache, drowsiness, visual disturbances, cardiovascular collapse, convulsions, hypokalemia, rhythm and conduction disorders including QT prolongation, torsades de pointes, ventricular tachycardia, and ventricular fibrillation. This may progress to sudden respiratory and cardiac arrest. Overdose should be treated with immediate gastric lavage and activated charcoal at a dose of at least 5 times the hydroxychloroquine dose within 30 minutes. Parenteral diazepam may be given to treat cardiotoxicity, transfusion may reduce serum concentrations of drug, patients should be monitored for at least 6 hours, fluids should be given, and ammonium chloride should be given to acidify urine and promote urinary excretion. Patients may also be given epinephrine.

Originator

Plaquenil,Winthrop,US,1956

The Uses of Hydroxychloroquine

Hydroxychloroquine is used to treat autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, in addition to malaria.
Hydroxychloroquine is a disease-modifying anti-rheumatic drug (DMARD). It regulates the activity of the immune system, which may be overactive in some conditions. Hydroxychloroquine can modify the underlying disease process, rather than simply treating the symptoms.
Hydroxychloroquine is used to treat:
rheumatoid arthritis
discoid and systemic lupus erythematosus (SLE)
juvenile idiopathic arthritis (JIA).
Over the long term hydroxychloroquine can reduce pain, swelling and joint stiffness. If you have lupus, it may also improve the rash. It may be as long as 12 weeks before you notice the benefits.

Indications

Hydroxychloroquine is indicated for the prophylaxis of malaria where chloroquine resistance is not reported, treatment of uncomplicated malaria (caused by P. falciparum, P. malariae, P. ovale, or P. vivax), chronic discoid lupus erythematosus, systemic lupus erythematosus, acute rheumatoid arthritis, and chronic rheumatoid arthritis.

Background

Hydroxychloroquine is a racemic mixture consisting of an R and S enantiomer. Hydroxychloroquine is an aminoquinoline like chloroquine. It is a commonly prescribed medication in the treatment of uncomplicated malaria, rheumatoid arthritis, chronic discoid lupus erythematosus, and systemic lupus erythematosus. Hydroxychloroquine is also used for the prophylaxis of malaria in regions where chloroquine resistance is unlikely. It was developed during World War II as a derivative of quinacrine with less severe side effects. Chloroquine and hydroxychloroquine are both being investigated for the treatment of SARS-CoV-2.
The FDA emergency use authorization for hydroxychloroquine and chloroquine in the treatment of COVID-19 was revoked on 15 June 2020.
Hydroxychloroquine was granted FDA approval on 18 April 1955.
A recent study reported a fatality in the group being treated with hydroxychloroquine for COVID-19.

Definition

ChEBI: An aminoquinoline that is chloroquine in which one of the N-ethyl groups is hydroxylated at position 2. An antimalarial with properties similar to chloroquine that acts against erythrocytic forms of malarial parasites, it is mainly used s the sulfate salt for the treatment of lupus erythematosus, rheumatoid arthritis, and light-sensitive skin eruptions.

Indications

Hydroxychloroquine (Plaquenil), like chloroquine, is a 4-aminoquinoline derivative used for the suppressive and acute treatment of malaria. It also has been used for rheumatoid arthritis and discoid and systemic lupus erythematosus. Hydroxychloroquine has not been proved to be more effective than chloroquine. Adverse reactions associated with its use are similar to those described for chloroquine.The drug should not be used in patients with psoriasis or porphyria, since it may exacerbate these conditions.

Manufacturing Process

A mixture of 323 grams of 1-chloro-4-pentanone, 480 grams of N-ethyl-N-2- hydroxyethylamine and 400 grams of sodium chloride (to aid in subsequent filtration) in 1.3 liters of xylene was heated with stirring on a steam bath for two hours and then refluxed for three hours. After standing overnight, the mixture was filtered and the filter cake washed with xylene. The filtrate was fractionally distilled, yielding 207.3 grams of a fraction distilling at 89° to 90°C at 0.35 mm; nD25 = 1.4600. This fraction, 1-(N-ethyl-N-2- hydroxyethylamino)-4-pentanone, was used in the next step of the synthesis. A sample of the fraction was further purified by distillation through a column and gave an analytically pure sample of 1-(N-ethyl-N-2-hydroxyethylamino)- 4-pentanone, boiling at 85° to 87°C at 0.4 mm.
The 1-(N-ethyl-N-2-hydroxyethylamino)-4-pentanone from above (284.2 grams) was dissolved in 300 grams of 28% ammoniacal methanol and reduced catalytically with Raney nickel (at an initial pressure of 1,000 pounds) at room temperature. After 24 hours the catalyst was filtered off and the product distilled in vacuo through a column, yielding 254 grams of a fraction distilling at 88.5° to 96°C at 0.3 mm and comprising mainly 5-(N-ethyl-N-2- hydroxyethylamino)-2-pentylamine. An analytical sample of this fraction distilled at 93°C at 0.6 mm.
A mixture of 90 grams of 4,7-dichloroquinoline, 90 grams of phenol, 1 gram of potassium iodide and 132 grams of 5-(N-ethyl-N-2-hydroxyethylamino)-2- pentylamine from above was heated with stirring for 13 hours at 125° to 130°C. Methanol (1.9 liters) was added and the the mixture was filtered with charcoal. The filtrate was treated with 270 cc of a solution of 100 grams of phosphoric acid in 300 cc of methanol. The walls of the flask containing the filtrate were scratched with a glass rod and the mixture was allowed to stand for two days. The solid was filtered off, washed with methanol and dried, yielding 101 grams of crude 7-chloro-4-[5-(N-ethyl-N-2-hydroxyethylamino)- 2-pentyl]aminoquinoline diphosphate, MP 155° to 156°C.
Additional quinoline diphosphate was obtained as a gummy mass from the filtrate by concentrating the latter to about half its volume and adding acetone. The crude gummy diphosphate was dissolved in water, basified with ammonium hydroxide and the resulting liberated basic quinoline extracted with chloroform. After removal of the chloroform by distillation, the residue was dissolved in ether and crystallization was induced by scratching the walls of the flask with the glass rod. About 30 grams of the crude quinoline base, melting at 77° to 82°C, separated. Recrystallization of this material from ethylene dichloride or ethyl acetate yielded the purified 7-chloro-4-[5-(Nethyl-N-2-hydroxyethylamino)2-pentyl] aminoquinoline, MP 89° to 91°C. The base may then be dissolved in ethanol and precipitated as the sulfate by reaction with an equimolar quantity of sulfuric acid.

Therapeutic Function

Antimalarial

Mechanism of action

Hydroxychloroquine, like chloroquine, is also used for treating acute forms of malaria caused by P. vivax, P. malariae, P. ovale, and also sensitive forms of P. falciparum. It is also effective and safe like chloroquine, although it does not have obvious advantages. The only advantage is that it is somewhat better tolerated. Its use is somewhat more limited than chloroquine. Synonyms of this drug are plaquenil, quensyl, toremonil, and others.

Pharmacokinetics

Hydroxychloroquine affects the function of lysosomes in humans as well as plasmodia. Altering the pH of the lysosomes reduces low-affinity self-antigen presentation in autoimmune diseases and interferes with the ability of plasmodia to proteolyze hemoglobin for their energy requirements. Hydroxychloroquine has a long duration of action as it may be taken on a weekly basis for some indications. Hydroxychloroquine may lead to severe hypoglycemia and so diabetic patients are advised to monitor their blood glucose levels.
Hydroxychloroquine is active against the erythrocytic forms of chloroquine-sensitive strains of P. falciparum, P. malariae, P. vivax, and P. ovale. Hydroxychloroquine is not active against the gametocytes and exoerythrocytic forms including the hypnozoite liver stage forms of P. vivax and P. ovale. Hydroxychloroquine is not effective against malaria in areas where chloroquine resistance has been reported.

Clinical Use

Hydroxychloroquine is approved for the treatment of both systemic and cutaneous lupus erythematosus. Both chloroquine and quinacrine (Atabrine) are also effective in this skin disease. Low-dose chloroquine is used for the therapy of porphyria cutanea tarda in patients in whom phlebotomy has failed or is contraindicated. Other skin diseases in which the drugs are useful (after sunscreens and avoidance of sun exposure) include polymorphous light eruption and solar urticaria.

Synthesis

Hydroxychloroquine, 7-chloro-4-[4-[ethyl(2-hydroxyethyl)amino]- 1-methylbutylamino]quinoline (37.1.1.19), is made by a scheme similar to that of making chloroquine. Reacting 1-chloro-4-pentanone with 2-ethylaminoethanol gives the corresponding aminoketone (37.1.1.17), which undergoes reductive amination in conditions analogous to those described above, making 4-[ethyl(2-hydroxyethyl)amino]-1-methylbutylamine (37.1.1.18). Reacting this with 4,7-dichlroquinoline (37.1.1.1) makes the desired hydroxychloroquine.

Metabolism

Hydroxychloroquine is N-dealkylated by CYP3A4 to the active metabolite desethylhydroxychloroquine, as well as the inactive metabolites desethylchloroquine and bidesethylchloroquine. Desethylhydroxychloroquine is the major metabolite.