Anti-malarial drugs Flashcards
Four species of plasmodium typically cause human malaria
Plasmodium falciparum
P vivax
P malariae
P ovale
Which specie is responsible for the majority of serious complications and deaths?
P falciparum
Malaria
-Parasite life cycle
- mosquito inoculates sporozoites to initiate human infection
- sporozoites invade liver cells –> exoerythrocytic stage: tissue schinzonts mature in the liver
- from liver –> merozoites. Only erythrocytic parasites cause clinical illness
- Sexual stage gametocytes also develop in erythrocytes before being taken up by mosquitoes, where they develop into –> infective sporozites
- in P falciparum and P malariae infection, treatment that eliminates erythrocytic parasites will cure these infections
- in P vivax and P ovale infections, a dormant hepatic stage, the hypnozoite, is not eradicated by most drugs and relapses can occur
- Which stage of infections causes clinical malaria?
2. All effective antimalarial treatment are?
- Only the asexual erythrocytic stage
2. Blood schinzonticides that kill this stage
Only drug that is able to kill quiescent hypnozoites
Primaquine
Drugs that act on hepatic schizonts during initial infection
Atovaquone-proguanil
Drugs that act on blood-stage schinzonticides
Atovaquone–proguanil,
Doxycycline,
Mefloquine,
Chloroquine
Antimalarial drugs
-treatment
- Chloroquine –> most nonfalciparum and falciparum infections from areas without known resistance
- Malarone (atavaquone and proguanil) –> uncomplicated falciparum malaria from most areas
- Mefloquine, quinine, halofantrine –> against resistant falciparum malaria
- Intravenous artesunate, quinidine, quinine –> severe falciparum malaria
- Primaquine –> Vivax and ovale malaria, to eradicate liver forms
Chloroquine
- pharmacokinetics
- action
-initial 1/2 life of 3-5 days but much longer terminal elimination 1/2 of 1-2 month
- effective against blood and gameto forms
- preventing the biocrystallization of the hemoglobin breakdown product heme into hemozoin –> accumulation of heme is toxic to the parasite
- highly effective blood schonzonticide
- not active against liver stage
Chloroquine
- basis of resistance
- clinical uses
-mutations in putative transporter
- chemoprophylaxis of malaria, amebic liver abscesses, rheumatological diseases
- treatment of uncomplicated malaria,
- rapidly terminates fever and clears parasitemia,
- does not eliminate dormant liver forms of P vivax and P ovale –> primaquine
Chloroquine
-adverse effects
- usually well tolerated
- ECG changes, severe hypotension, dermatitis
-safe in pregnancy and for young children
Quinine
- pharmacokinetics
- action
-effective in blood and gameto forms
- mechanism of action is unknown
- gametocidal against P vivax and P ovale
- not active against liver stage parasites
Quinine
-clinical uses
- treatment of severe palciparum malaria (i/v)
- treatment of falciparum malaria (oral)
- severe, uncomplicated malaria commonly with second drug (doxycycline, in children with clindamycin)
- generally not used for chemoprophylaxis
Quinine
- unwanted effects
- contraindications and drug interactions
- cinchonism (visual and hearing disturbances, GI distress, headache, virtigo)
- hypoglycemia
- blackwater fever
- underlying visual and auditory problems
- should not be given together with mefloquine
Mefloquine
- pharmacokinetics
- action
-elimination 1/2 life is about 20 days
- mechanism of action is unknown
- strong blood schinzonticidal activity against P falciparum and P vivax
- not active against hepatic stages or gametocytes