Chloroquine is a medication primarily used to prevent and treat malaria in areas where malaria remains sensitive to its effects. Certain types of malaria, resistant strains, and complicated cases typically require different or additional medication. Chloroquine is also occasionally used for amebiasis that is occurring outside the intestines, rheumatoid arthritis, and lupus erythematosus. While it has not been formally studied in pregnancy, it appears safe. It was studied to treat COVID-19 early in the pandemic, but these studies were largely halted in the summer of 2020, and is not recommended for this purpose. It is taken by mouth.Common side effects include muscle problems, loss of appetite, diarrhea, and skin rash. Serious side effects include problems with vision, muscle damage, seizures, and low blood cell levels. Chloroquine is a member of the drug class 4-aminoquinoline. As an antimalarial, it works against the asexual form of the malaria parasite in the stage of its life cycle within the red blood cell. How it works in rheumatoid arthritis and lupus erythematosus is unclear.Chloroquine was discovered in 1934 by Hans Andersag. It is on the World Health Organizations List of Essential Medicines. It is available as a generic medication. Medical uses
Malaria
Chloroquine has been used in the treatment and prevention of malaria from Plasmodium vivax, P. ovale, and P. malariae. It is generally not used for Plasmodium falciparum as there is widespread resistance to it.Chloroquine has been extensively used in mass drug administrations, which may have contributed to the emergence and spread of resistance.
Acute flaccid myelitis (AFM) is a serious condition of the spinal cord. Symptoms include rapid onset of arm or leg weakness and decreased reflexes. Difficulty moving the eyes, speaking, or swallowing may also occur. Occasionally, numbness or pain may be present. Complications can include trouble breathing.The cause of most cases is unclear as of 2018. More than 90% of recent cases have followed a mild viral infection such as from enteroviruses. While polio can cause AFM, since 2014, it has not been involved in cases in the United States. The underlying mechanism involves damage to the spinal cords grey matter. Diagnosis may be supported by medical imaging of the spine, nerve conduction studies, and cerebrospinal fluid testing.Treatment involves supportive care. Physical therapy may be recommended. Occasionally, mechanical ventilation is required to support breathing. Outcomes are variable. The condition is rare and occurs most commonly in children. Fewer than one in 500,000 children is affected per year in the United States. Although the illness is not new, an increase in cases has been seen since 2014 in the United States. In 2018,  233 cases were confirmed in the United States. Signs and symptoms
Symptoms include:

Difficulty moving the eyes or drooping eyelids
Facial droop or weakness
Difficulty with swallowing or slurred speech
Sudden arm or leg weaknessA summary of the condition by the Centers for Disease Control and Prevention (CDC) in 2014:
Common features included acute focal limb weakness and specific findings on magnetic resonance imaging (MRI) of the spinal cord consisting of nonenhancing lesions largely restricted to the grey matter.