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What is Chloroquine?

Chloroquine is a synthetic drug mainly used for the treatment of malaria. Chloroquine was discovered in 1934, it started to practice for the medical needs in the 1940s. It is one of the quinoline derivatives and a member of chemically related antimalarial agents. This chloroquine is tearmed chloroquine phosphate. chloroquine hydrochloride can also use as an intramuscular injection.  Chloroquine and hydroxychloroquine are closely related to each other. This is another derivative of quinoline.  Hydroxychloroquine can also be used for treating inflammatory rheumatic diseases and malaria. 

Chloroquine Chemical Structure

The chemical formula for Chloroquine is C₁₈H₂₆ClN₃. The chloroquine chemical structure 7-chloro-4-(4-diethylamino-1-methyl butyl amino)-quinoline, is formed while 4,7-di chloroquinoline is reacted with 4-diethylamino-1-methyl butylamine at 180 °C. 

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This image shows the chloroquine structure and IUPAC name. 

Mechanism of Chloroquine 

The chloroquine has a lysosomotropic character, which helps to perform as an antimalarial drug. Chloroquine drug concentrates on acidic food vacuole of the parasite and enters into the essential process. The lysosomotropic properties allow it for the use of in vitro experiments pertaining to intracellular lipid-related disease namely apoptosis and autophagy.  

The malarial parasite present in the red blood cells undergoes an asexual lifecycle. It starts affecting the hemoglobin to acquire essential amino acids. As the parasite requires to build its own protein and energy metabolism.  The digestion of the parasites carries out in a vacuole of the cells. Hemoglobin composed of protein unit and heme unit. The parasite can digest protein units but cannot synthesize heme units. During the digestion process, parasites release the toxic, soluble molecule heme unit. This heme unit consists of the porphyrin ring called  Fe(II)-protoporphyrin IX (FP). To avoid destruction by this molecule,  hemozoin is formed by the parasite biocrystallizes heme. Hemozoin gets stored in a digestive vacuole as insoluble crystals. 

Chloroquine entering the red blood cells. It inhibits the parasite cell and digestive vacuole for the diffusion process. Chloroquine transfers CQ2+ protons as the digestive vacuole is acidic. So, the parasite cannot go for the diffusion process.  Chloroquine covers hemozoin molecules to prevent further biocrystallization of heme thus helps to heme buildup. 


The chloroquine join to heme to form the FP-chloroquine complex. This gets high toxic to the cell and disturbs the membrane function. The action of the toxic FP and FP- chloroquine results in cell lysis and supports parasite cell autodigestion. If the parasite does not form hemozoin, then it is resistant to chloroquine. 

P. falciparum is a resistant strains of chloroquine. These strains are showing resistant behaviour to chloroquine this is because mainly due to the evolution of species. It was discovered in East and West Africa, Southeast Asia, and South America. The resistant parasites use its transmembrane pump to remove chloroquine from the digestive vacuole. These chloroquine-resistant parasites pump out 40 times more than the chloroquine-sensitive parasites. P. falciparum codes the pump by the chloroquine resistance transporter (PfCRT) gene. The main function of the chloroquine pump is to transport peptides. A Ca²⁺ channel blocker Verapamil has found to restore the ability of chloroquine to treat resistance parasites. 

Chloroquine Uses

Chloroquine is an effective agent to act against the susceptible strains of malarial parasites Plasmodium ovale, Plasmodium vivax, and Plasmodium falciparum and some parasitic worms and amoebas. It can also be used for the treatment of inflammatory rheumatic diseases namely rheumatoid arthritis and lupus erythematosus.

Chloroquine Side Effects

Chloroquine tablet uses brings some side effects. The chloroquine side effects vary depends on the individual’s immune power. Chloroquine phosphate uses have mild side effects like abdominal cramps and headache, it is a common effect of all antimalarial drugs. They may also experience tinnitus, skin rashes, nausea, vomiting, muscle weakness, visual impairment, and changes in behaviour. Visual impairment is mainly due to retinal damage. This may occur only due to the long-term chloroquine phosphate uses. This condition of experiencing visual impairment is known as chloroquine retinopathy. 

This chloroquine will interact with other medications namely, antibiotics like ampicillin, erythromycin, antacids, antiarrhythmics which increases side effects. Drug-to-drug interactions will alter the chloroquine interaction level in the body. It may block the chloroquine metabolism, which results in toxic chloroquine accumulation in the body. Also, chloroquine has the potential to alter the level of other drugs. This increases the toxicity of the agent and the risk of side effects. A similar derivative of quinoline, hydroxychloroquine has many side effects as chloroquine. But, it is comparatively less toxic. 

How to Use Chloroquine Phosphate? 

Chloroquine phosphate can intake in the form of tablets. Chloroquine tablet uses for treating malaria and amebiasis. To prevent malaria in adults, can use one dose of the tablet for one week. That should take on the same day of the week. The dosage level must be determined by the doctors. It is preferable to take one dose of chloroquine hydrochloride before 2 weeks or after 8 weeks for travelling to the malaria-affected areas. If a person severely affected by malaria, the physician will prefer to take an extra half a dose after 6 to 8 hours of taking one dose of tablets. For treating or preventing children from malaria, physicians calculate the amount of chloroquine phosphate level based on children’s weight. 

For treating amebiasis, it is recommended to take one dose of tablets for 2 days and a half dose of tablets every 2 to 3 weeks. chloroquine tablet can be taken with other amebicides medicine. 

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FAQs on Chloroquine

Q1. What Chloroquine is Used for?

Ans: Chloroquine phosphate is a widely used medicine for treating and preventing malaria. These are also used for treating amebiasis. Chloroquine phosphate belongs to the drug class called amebicides and antimalarials. The Aralen is a brand name for the antimalarial drug, chloroquine. Hydroxychloroquine is similar to chloroquine and it is useful for treating amebiasis and several forms of malaria. This can treat amebiasis which is spread outside the intestine. 

Q2. What is the Side Effect of Chloroquine?

Ans: The patients intaking chloroquine may have effects like headache, nausea, vomiting, diarrhea, and abdominal cramps. It is preferable to consult a physician if it lasts a longer duration. The serious side effects of quinine include abnormal heartbeat, a bleeding problem, kidney damage, visual impairments. Researchers proved that the continuous intake of chloroquine impacts the function of the kidney. This is due to the Na+ and Cl retention. This can be controlled by providing chloroquine-induced increases in plasma aldosterone concentration and lowering GFR. But chloroquine does not have any relationship with serum enzyme level elevations. In rare cause, it may cause liver injury. 

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