Schizonticides

Tissue Schizonticides. These eradicate the Hver stages of the parasite and thereby prevent their entry into the blood. As a class, therefore, they ate useful for prophylaxis. Some tissue schizonticides can act on the long-Hved tissue forms (hypnozoites) of P. vivax and P. ovale and thus can cure the latter infections by preventing relapses. 

Blood Schizonticides. These destroy the erythrocytic stages of the parasites and are useful for the clinical cure of falcipamm malaria or suppression of relapsing infections. 

The dmgs known as antifolates act as effective blood schizonticides. Unfortunately, the parasites readily develop resistance to them. Most antifolates show poor oral tolerance, absorption, and host toxicity. They fall into two types depending on the mechanisms by which they operate. 

Antimalarial therapy employs the same agents and is based on the same principles. The blood-schizonticidal halofantrine is reserved for therapy only. The pyrimethamine-sulfadoxine combination may be used for initial selftreatment. 

Mefloquine is also a 4-aminoquinoline. It is a blood schizonticide active against the asexual stages of all malaria parasites. Mefloquine is currently the prophylactic agent of choice for short-term travellers. Resistance of P. falciparum against mefloquine has occurred in South-East Asia. Only an oral... 

VI.a.2.2. Biguanides. Proguanil is a dihydrofolate reductase inhibitor. It is a slow acting blood schizonticide and not effective on its own. It has also a marked effect on the primary tissue stages of Plasmodium falciparum. It is used in combination with chloroquine for the prophylaxis of chloroquine-resistant Plasmodium falciparum. 

Quinine is the principal alkaloid derived from the bark of the cinchona tree. It has been used for malaria suppression for over 300 years. By 1959 it was superseded by other drugs, especially chloroquine. After widespread resistance to chloroquine became manifest quinine again became an important antimalarial. Its main uses are for the oral treatment of chloroquine-resistant falciparum malaria and for parenteral treatment of severe attacks of falciparum malaria. Quinine is a blood schizonticide with some gametocytocidal activity. It has no exoerythrocytic activity. Its mechanism of action is not well understood. It can interact with DNA, inhibiting strand separation and ultimately protein synthesis. Resistance of quinine has been increasing in South-East Asia. 

Halofantrine, a 9-phenanthrenemethanol derivative, is a blood schizonticide and is active against Plasmodium vivax and chloroquine sensitive as well as chloroquine resistant strains of Plasmodium falciparum. As no parenteral preparation is available it cannot be used for severely ill patients. Oral absorption is slow and incomplete and is increased by a fatty meal. 

Quinacrine, a 9-aminoacridine, is a blood schizonticide with activity against all four types of... 

While its detailed mechanism of action is unknown, it is an effective blood schizonticide that is, it acts against the form of the parasite responsible for chnical symptoms. Orally administered mefloquine is well absorbed and has an absorption half-hfe of about 2 hours the elimination half-hfe is 2 to 3 weeks. Among its side effects are vertigo, visual alterations, vomiting, and such CNS disturbances as psychosis, hallucinations, confusion, anxiety, and depression. It should not be used concurrently with compounds known to alter cardiac conduction or prophylactically in patients operating dangerous machinery. It should not used to treat severe malaria, as there is no intravenous formulation. 

Mechanism of Action An antiprotozoal with blood and some tissue schizonticidal ac-tivityagainst malaria parasites of humans. Highly selective activity against plasmodia and Toxoplasma gondii. Therapeutic Effect Inhibition of tetrahydrofolic acid synthesis. 

It is a highly effective erythrocytic schizonticide especially against mature trophozoite and schizont forms of malarial parasite. 

It shows rapid schizonticidal action and brings about quick clinical improvement in falciparum malaria with low recrudescence rate. It has some gametocidal action too. 

It is a schizonticidal drug and leads to destruction of asexual erythrocytic forms... 

Life cycle of malaria parasites. Only the asexual erythrocytic stage of infection causes clinical malaria. All effective antimalarial treatments are blood schizonticides that kill this stage. 

When not limited by resistance, chloroquine is a highly effective blood schizonticide. It is also moderately effective against gametocytes of P vivax, P ovale, and P malariae but not against those of P falciparum. Chloroquine is not active against liver stage parasites. 

Mefloquine has strong blood schizonticidal activity against P falciparum and P vivax, but it is not active against hepatic sta-ges or gametocytes. The mechanism of action of mefloquine is unknown. 

Artemisia annua L. A. apiacea Hance ex Walpers Qing Guo (Stinking artemisia) (aerial part) Dihydroartemisinin, artesunate, artemisinin, chloroquine, flavonoids, sesquiterpene.33-269-476 This herb is mildly toxic. A schizonticidal agent, antimalarial, treat infections of multidrug-resistant strains of Plasmodium falciparum, the cause of human malignant cerebral malaria. 

Artemisia annua L. China Dihydroartemisinin, artesunate, artemisinin, chloroquine.33 This herb is mildly toxic. A schizonticidal agent, antimalarial. 

Secondary tissue schizonticides. Agents such as primaquine destroy exoerythrocytic tissue schizonts such as those developing in the liver. 

Primaquine [PRIM a kwin] is an 8-aminoquinoline that eradicates primary exoerythrocytic forms of R falciparum and R vivax and the secondary exoerythrocytic forms of recurring malarias (R vivax and R ovale). In addition, the sexual (gametocytic) forms of all four plas-modia are destroyed in the blood or are prevented from maturing later in the mosquito. Because of its lack of activity against the erythrocytic schizonts, primaquine is often used in conjunction with a schizonticide. 

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