Antiprotozoals

Question 1

Artemether with lumefantrine/benflumetol

Answer 1

Antimalarial

Artemether (an artemisinin) is metabolised to the active metabolite artenimol (dihydroartemisinin). Combination acts in the food vacuole of the malaria parasite interfering with the conversion of haem to nontoxic haemozoin; also inhibits nucleic acid and protein synthesis.

Question 2

Atovaquone with proguanil

Answer 2

Antimalarial

Ubiquinone analogue; thought to selectively inhibit protozoal mitochondrial electron transport at the cytochrome bc1 complex and reduce pyrimidine biosynthesis, preventing protozoal replication.

Proguanil is converted to cycloguanil (active metabolite), which is a plasmodial dihydrofolate reductase inhibitor.

The combination of atovaquone and proguanil is synergistic.

Question 3

Chloroquine

Answer 3

Antimalarial SAS product

Rapidly acting schizonticide with some gametocytocidal activity.

Interferes with DNA or RNA synthesis; increases intravacuolar pH; causes haem accumulation by inhibiting its polymerisation, resulting in parasite death.

It has anti-inflammatory activity and may also have immunosuppressive effects.

Question 4

Mefloquine

Answer 4

Antimalarial

Mefloquine may form toxic complexes with free haem that damage membranes and interact with other plasmodial components.

Question 5

Primaquine

Answer 5

Antimalarial

Tissue schizonticide effective against intrahepatic forms of P. vivax and P. ovale. Mode of action unclear. Also gametocytocidal against P. falciparum.

Question 6

Quinine

Answer 6

Antimalarial

Quinine may inhibit plasmodial haem polymerase causing haem accumulation (toxic to parasite membranes); interferes with DNA or RNA synthesis; binds to haemoglobin protease; increases intravacuolar pH.

Question 7

Tafenoquine

Answer 7

Primaquine antimalarial

Interferes with parasite’s mitochondrial function and causes accumulation of haem which is toxic to the parasite

Question 8

Paromomycin

Answer 8

Aminoglycoside SAS product

Amoebiasis due to E. histolytica (to eradicate pathogenic cysts in the GIT either in asymptomatic infection or after treatment of invasive or symptomatic intestinal disease with metronidazole)

Question 9

Pyrimethamine

Answer 9

SAS product

Folic acid antagonist.