Health Centres - Avloclor
How does it work?
Avloclor tablets contain the active ingredient chloroquine phosphate, which is an antimalarial medicine, though it also has other uses, for example, in treating the autoimmune diseases rheumatoid arthritis and lupus erythematosus.
Malaria is a potentially fatal disease caused by various types of single-celled (protozoan) parasites known as Plasmodium. Plasmodium are carried by mosquitoes and injected into the bloodstream during a bite from an infected mosquito. Once in the blood, the parasites travel to the liver, where they multiply. The parasites are then released back into the bloodstream where they invade the red blood cells and multiply again. An actual attack of malaria develops when the red blood cells burst, releasing a mass of parasites into the bloodstream. The attacks do not begin until a sufficient number of blood cells have been infected with parasites.
Chloroquine works by attacking the parasites once they have entered the red blood cells. It kills the parasites and prevents them from multiplying further.
It is not fully understood how chloroquine kills the parasites, but it is thought to work by blocking the action of a chemical that the parasites produce to protect themselves once inside the red blood cells. When inside the red blood cells, the malaria parasites digest the oxygen carrying pigment haemoglobin that is found in these cells. This divides the haemoglobin into two parts; haem and globin, and the haem part is toxic to the malaria parasite. To prevent itself from being damaged by haem, the malaria parasite produces a chemical that converts haem into a compound that is not toxic to them. Chloroquine blocks the action of this chemical. This causes the levels of the toxic haem to rise, thus killing the malaria parasites.
Chloroquine can be used both to prevent and to treat malaria. For prevention it is usually taken in combination with another antimalarial medicine called proguanil. However, the malaria parasite is resistant to these medicines in certain areas of the world, and it is important to check with your pharmacist which medicines are currently recommended to prevent malaria in the country you are travelling to. You can also check in the travel section of this site.
If chloroquine is recommended for prevention it should be started a week before travel to the malarious region. It should then be taken throughout the stay, so that if you are bitten by an infected mosquito, there will be medicine in your blood to prevent malaria developing. Chloroquine should be continued for a further four weeks after leaving the malarious area, so that there is still medicine in the blood to kill any remaining parasites released from the liver into the red blood cells during this time.
Higher doses than those used for preventing malaria are used to treat malaria infection.
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