Anti-Parasite Drugs
Anti-malarial drugs
These drugs target various stages of the malaria parasite life cycle.
Chloroquine
It raises the pH of parasite vacuoles inhibiting haem-polymerase
– This stops the parasite feeding in RBCs stopping the life cycle
– It is taken weekly and used in malaria prophylaxis and attacks
– It is also used an anti-inflammatory in autoimmune disorders
Side effects
• Headache + Contraindicated in epilepsy
• Unfortunately, resistance to chloroquine is emerging in many species of P. Falciparum.
Mefloquine
This acts similarly to chloroquine and is used for prophylaxis and treatment of chloroquine-resistance strains
Side effects
• Dizziness + Psychiatric signs (suicidal thoughts)
Contraindications
- Epilepsy
Quinine
This interferes with the erythrocytic stage of the parasite by inhibiting its ability metabolise haem
– Quinine is used in the management of P. Falciparum that has become resistant to chloroquine.
Side effects
• Produces curare-like effects on skeletal muscle + tinnitus + visual disturbances
• Blackwater fever –> a haemolytic crisis that occasionally complicates malaria infection.
• Large numbers of red blood cells undergo haemolysis releasing haemoglobin into the bloodstream
• This can cause an AKI.
Artemisinins
e.g. Dihydroartemisin + Artensuante
These are semi-synthetic drugs which are used in combination therapy to treat P. Falciparum
– They are broken down to dihydroartemisinin which generates free radicals to kill the parasite
Side effects
• GI upset
• Dizziness
Fansidar
This is Pyrimethamine (inhibits dihydrofolate reductase) + Sulfadoxine (inhibits dihydropteroate synthase)
– Acts to prevent folic acid synthesis prevent DNA synthesis –> used to treat P. Falciparum
Side effects
• Megaloblastic anaemia
• Folate deficiency
Proguanil
This is a prodrug whose active metabolite inhibits dihydrofolate reductase to stop parasite DNA synthesis
– It is commonly used in combination with chloroquine or atovaquone (electron transport chain inhibitor)
Drugs against other parasites
Mebendazole
This drug is used to treat many parasitic worm infections including threadworms, hookworms and giardia
– It inhibits the synthesis of microtubules which stops uptake of glucose and nutrients killing the helminth
Side effects
• GI upset
• Hepatotoxicity
Praziquantel
This drug is most famous for treating schistosomiasis arguably by increasing cell permeability to Ca2+
Side effects
• GI upset
• CNS disturbance (dizziness, headache)
Ivermectin
Used against parasites like head lice, scabies. It opens Cl– channels causing cell hyperpolarization and death
Side effects
• CNS depression
• Ataxia
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