Anti Parasite

Primaquine indication

TISSUE schizonticide → Used to eradicate primary exoerythrocytic (liver/tissue) form of plasmodium and relapse of secondary form in P.vivax and ovale

Primaquine mechanism of action

Metabolites are oxidants → Schizonticidal action

Primaquine AE

Hemolytic anemia in G6PD px; CI in pregnancy; hemolysis and methemoglobinemia

Chloroquine indication

BLOOD schizonticide; used to treat P falciparum; used as prophylaxis

Toxoplasmosis drugs

Pyrimethamine

Antimalaria drugs

Primaquine, Chloroquine, Atovaquone-proguanil, Mefloquine, Quinine,

Pyrimethamine, Artesunate

Amebiasis, giardia drugs

Metronidazole, Tinidazole

Trypanosomiasis drugs

Pentamidine

Nematodes drugs

Mebendazole, Pyrantel pamoate, Thiabendazole, Ivermectin, Diethylcarbamazine

Cestodes drugs

Niclosamide, Albendazole

Trematodes drugs

Praziquantel

Chloroquine ADME

Penetrate CNS and placenta, dealkylated in liver and excrete in urine

Chloroquine AE

Low dose = low side effect, high dose= GI upset, headache etc; caution in CNS disorder and liver/GI disease; avoid in Px with porphyria and heart disease

Quinine indication

BLOOD schizonticide; used for SEVERE chloroquine resistant strain; use with doxy, tetra and clinda

Quinine mechanism of action

Interfere with heme polymerization → Erythrocytic form death

Quinine AE

Reversible cinchonism (N/V, tinnitus, vertigo), hematotoxic → Blackwater fever, fetotoxic

Artemisinin/Artesunate indication

BLOOD schizonticide; FIRST LINE in multi drug resistant P. falciparum

Artemisinin/Artesunate mechanism of action

Produce free radicals after being cleaved → blood cell death

Artemisinin/Artesunate AE

Neurotoxic and prolonged QT in extremely high dose

Mefloquine indication

BLOOD schizonticide; prophylaxis and treatment of multidrug resistant P. falciparum

Mefloquine AE

Quinine/quinidine concurrent use causes ECG abnormalities and cardiac arrest; CI in pregnancy

Atovaquone-proguanil indication

Prevent and treat malaria; used for chloroquine resistant falciparum

Pyrimethamine indication

BLOOD schizonticide; used for P falciparum and T. gondii

Pyrimethamine mechanism of action

Inhibit dihydrofolate reductase in plasmodium and tetrahydrofolate in protozoa → cannot do de novo synthesis

Pyrimethamine AE

Megaloblastic anemia → Reverse with folinic acid

Toxoplasmosis treatment of choice

Pyrimethamine + sulfadiazine

Metronidazole indication

Used for Giardia lamblia, Trichomonas vaginalis, anaerobic cocci, and anaerobic gram-negative bacilli, pseudomembraneous colitis

Metronidazole mechanism of action

Nitro group is electron acceptor → lower cytotoxin compound → Bind to protein and DNA → E. histolytica death

Metronidazole AE

Nausea, vomiting, oral moniliasis, disulfiram like reaction if taken with alcohol

What is tinidazole

Similar to metronidazole; just as effective with shorter period of treatment but more expensive

Pentamidine indication

T. brucei gambiense (hemolymphatic stage), prophylaxis for pneumocystis jirovecii infection + sulfa allergy, leishmaniasis alternative drug

Pentamidine mechanism of action

Interference with parasite RNA/DNA, phospholipid and protein synthesis; not clear

Pentamidine ADME

DOES NOT enter CNS → ineffective in trypanosomiasis second stage

Mebendazole mechanism

Inhibit microtubule assembly, block glucose uptake → Parasite expelled in feces

Mebendazole indications

Whipworms (Trichuris trichiura), Pinworms (Enterobius vermicularis), Hookworms (Necator americanus and Ancylostoma duodenale), Roundworms (Ascaris lumbricoides)

Pyrantel pamoate mechanism

Neuromuscular blocking agent → Activate nicotinic receptor → Contract + paralysis → expulsion of parasite

Pyrantel pamoate indication

Roundworm, pinworm and hookworm

Ivermectin mechanism of action

Target GABA → Increase Cl channel → Hyperpolarization → Paralysis and death

Diethylcarbamazine (DEC) mechanism of action

Immobilize microfilariae and alter surface structure → Parasite is more susceptible to host defense

Diethylcarbamazine (DEC) indication

W. bancrofti and Brugia malayi

Diethylcarbamazine (DEC) contraindicatino

Px with onchocerciasis → causes Mazzotti reaction

Praziquantel mechanism

Increase Ca entry → Increase contraction → Paralysis/vacuolization → death

Praziquantel indication

Schistosoma spp, Clonorchis sinensis, and Paragonimus westermani, off label for t. solium

Niclosamide indication

Intestinal fluke, cestode scolex, alternative to PZQ for taeniasis and cestode infection

Niclosamide mechanism

Inhibit ADP phosphorylation → no ATP

Albendazole mechanism

Inhibit microtubule assembly

Albendazole indication

Gnasthostoma spp, cysticercosis, hydatid disease