Antiparasitic

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Metronidazole

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- Oral nitroimidazole
- Treat luminal protozoal infections (giardia, trichomonas, E. histolytica) and anaerobic bacteria
- Transfers electron from pyruvate:ferredoxin oxidoreductase to form a free radical that adducts DNA/proteins/membranes
- Good penetration of CNS and abscesses
- Causes disulfiram-like effect, metallic taste, dizziness/vertigo, abdominal pain, and nausea

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Tinidazole

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- Oral nitroimidazole
- Treat luminal protozoal infections (giardia, trichomonas, E. histolytica) and anaerobic bacteria
- Similar mechanism and side effects as metronidazole, but longer half life and fewer GI side effects

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Paromomycin

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- Oral aminoglycoside
- Treat luminal protozoal infections (giardia, E. histolytica, Dientamoeba fragilis)
- Inhibits protein synthesis by causing mRNA misreading and freezing of 30S ribosomal subunit
- Can cause N/V, diarrhea, and abdominal cramps
- CI in renal disease (oto/renal/neuro toxicity)

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Nitazoxanide

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- Oral nitrosalicylamide
- Treat luminal protozoal infections in pediatric patients (giardia and cryptosporidium); may not work in AIDS patients
- Metabolized to tizoxanide/tizoxanide glucuonide, which interferes with pyruvate:ferredoxin oxidoreductase electron transfer in anaerobic metabolism
- Well tolerated, but may cause GI distress and headache

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Atovaquone

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- Oral antimalarial
- Combined with proguanil for prophylaxis/treatment of all forms of malaria
- Can be used for treatment/prophylaxic of pneumocystis jiroveci and toxoplasmosis
- Disrupts mitochondrial membrane of parasites
- Take with fatty meal
- May cause hsn, abdominal pain, N/V, diarrhea, rash or headache

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Proguanil

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- Oral antimalarial
- Combined with atovaquone for prophylaxis/treatment of all forms of malaria
- Metabolite cycloguanil is a DHF reductase inhibitor
- Causes synergistic mitochondrial membrane disrutpion with atovaquone
- Well absorbed orally
- May cause hsn, abdominal pain, N/V, diarrhea, rash or headache

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Doxycycline

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- Oral tetracycline
- Used alone for prophylaxis of MDR P. falciparum or combined with quinine/quinidine for acute malaria
- Interferes with tRNA access to 30S ribosomal subunit
- Antacids/Fe supplements (di/tri valent cations) interfere with absorption
- Causes teeth staining, decreased long bone growth, hepatotoxicity, photosensitivity, renal insufficiency, and superinfections
- CI in pregnancy and children

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Chloroquine

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- Oral/IV aminoquinolone
- DOC for prophylaxis/treatment of chloroquine-sensitive malaria (vivax/ovale/malaria tend to be sensitive; falciparum is developing reistance)
- No activity against hypnozoites
- Accumulates in acidic vesicles to elevate pH and increase concentration of toxic ferriprotoporphyrin IX via heme polymerase inhibition
- Very large Vd leads to tissue sequestration and slow release (given once/week)
- Frequently causes GI distress, headache, visual disturbances, fatigue, and confusion
- May cause hair depigmentation, partial alopecia, and exacerbate psoriasis
- Long-term high doses can lead to retinal degeneration

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Mefloquine

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- Oral fluoroquinoline
- Used for prophylaxis/treatment of chlorquine-resistant malaria (mainly P. falciparum)
- Unknown mechanism
- Dose-dependent GI effects and dizziness
- Can cause nightmares, vertigo, confusion, psychosis, and convulsions
- CI in pregnancy, epilepsy, psychiatric disorders, and concomitant beta-blockers

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Artemisinin derivatives (Artesunate/Artemether)

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- IM/IV/rectal wormwood derivatives
- DOC to treat MDR P. falicparum malaria and severe malaria
- Converted by intra-parasitic iron to free radicals and then alkylate malarial proteins
- Fast acting, but very short half-life, so they have to be used with a second drug to prevent relapses
- Very safe drugs

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Quinine

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- Oral cinchona alkaloid
- Clinical cure of chloroquine-resistant P. falciparum
- May work by similar mechanism to chloroquine (accumulation of toxic heme derivatives
- Causes cinchonism → dose-dependent tinnitus, vertigo, headache, dysphoria, N/V, diarrhea, visual disturbances, respiratory depression, and cyanosis
- Hypoglycemia is common in heavy malarial infections
- Increase effects of oral anticoagulants, digitalis, and NM blocking agents
- Barbiturates, primidone, and phenytoin decrease effects

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Quinidine

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- IV cinchona alkaloid
- Clinical cure of chloroquine-resistant P. falciparum
- Similar mechanism, side effects and drug interactions to quinine, but greater risk of shock due to alpha-adrenergic antagonism and myocardial depression

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Primaquine

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- Oral 8-aminoquinoline
- Used for radical cure of P. vivax/ovale, prophylaxis for P. vivax (and other plasmodium spp.)
- Interferes with mitochondiral function of tissue forms and gametocytes
- Causes hemolysis in G6PD deficient individuals and dose-dependent methemoglobinemia and cyanosis
- CI in G6PD deficiency and pregnancy

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Pyrimethamine

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- Oral diaminopyrimidin
- Treat toxoplasmosis with sulfadiazine
- Selective inhibitor of protozoal dihydrofolate reductase; synergistic with sulfadiazine
- Slowly absorbed and accumulates in lungs, liver, and kidneys
- Can cause megaloblastic anemia and is teratogenic in animals

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Sulfadiazine

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- Oral sulfonamide
- Treat toxoplasmosis with pyrimethamine
- PABA analog that acts as dihydrofolate reductase inhibitor; synergisitc with pyrimethamine
- Rapidly absorbed and eliminated unchanged renally
- Can cause skin rashes (Stevens-Johnson syndrome)
- Causes fever, skin rash, bone marrow suppression, and hepatotoxicity in most AIDS patients

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Trimethoprim-Sulfamethoxazole

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- Oral combination drug
- DOC for pneumocystis jiroveci pneumonia in AIDS and children with ALL
- Synergistic inhibition of tetrahydrofolate production; SMZ is PABA analog and TMP is dihydrofolate reductase inhibitor
- Non-immunocompromised → N/V, agranulocytosis, aplastic anemia, Stevens-Johnson syndrome, jaundice, and CNS effects
- AIDS → side effects in majority of patients; fever, malaise, rash, pancytopenia, neutropenia, thrombocytopenia, hepatits, GI side effects, and renal dysfunction
- Thiazide diuretics increase thrombocytopenia; prolonged PT with warfarin, and decreased phenytoin metabolism
- CI in pregnancy

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Pentamidine isethionate

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- IV/IM/aerosol aromatic diamidine
- Treat pneumocystis jiroveci pneumonia and hemolymphatic stage of trypanosoma brucie gamiense
- Interferes with nuclear metabolism and inhibits synthesis of DNA/RNA/protein/phospholipids
- IV delivery causes tachycardia, N/V, dizziness, blood dyscrasias, life-threatening hypotenion, hypoglycmia, and possible fatal pancreatitis
- IM causes pain and sterile abscess

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Albendazole

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- Oral benzididazole
- Single dose for nematodes (ascaris lumbricoides, hookworms, trichuris trichiura)
- Twice daily for one week for strongyloides stercoralis
- Also used for , enterobius vermicularis, capillaria philippinesis, inoperable echnococcal liver cysts, and neurocyticercosis
- Binds tubulin to disrupt polymerization and prevent glucose uptake in parasites
- Should be taken with fatty meal
- Metabolite albendazole sulphoxide is primarily responsibe for antihelmintic effects
- Concurrent corticosteroids raises drug levels

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Pyrantel pamoate

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- Oral pyrimidine derivative
- Treat enterobiasis, ascariasis, hookworm infection, trichostrongyliasis
- Not effective against whipworm
- Causes NM blockade (spastic paralysis) via nicotinic stimulation and inhibition of cholinesterases
- Causes mild side effects at high doses (GI symptoms, headache, rash, and fever)
- Mutually antagonistic with piperazine

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Diethylcarbamazine

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- Oral piperazine derivative
- Treat lymphatic filariasis and loa loa
- Multiple effects, including immobilization of parasites and increasing microfilarial surface membranes susceptibility to host's defense
- Placed in table salt some endemic areas
- Not used in onchocerciasis because it can cause Mazzotti reaction (pruritis, fever, hypotension, facial edmea, and eosiniphilia)
- Can cause eye complications (punctate keratitis, eveitis, retinal pigment atrophy), cerebral edema, and leukocytosis

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Ivermectin

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- Oral anti-helminth
- DOC for strongyloides steroralis, cutaneous larva migrans, and onchocerciasis (but does not kill adult worms)
- Also used in microfilaria and ectoparasites (scabies/pediculosis)
- Induces GABA release which leads to parasite paralysis and death (does not cross BBB into human CNS)
- Causes mild ithcing, swollen lymph nodes, dizziness, and postural hypotension

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Praziquantel

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- Oral pyrazinoisoquinoline derivative
- DOC for flukes (schisosoma) and tapeworms; not used for fasciola hepatica
- Low doses cause spastic paralysis and high doses cause vacuolization of parasite tegument to increase susceptibility to host defenses; both mechanisms are calcium dependent
- Can cause headache, dizziness, malaise, nausea, abdominal discomfort, and fatigue

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Permethrin

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- Cream/shampoo/spray pyrethin derivative
- Treat lice, ticks, fleas, and mites
- Disrupts Na-channels in parasite nerve cells to cause paralysis
- Use on clothes and bed nets to decrease mosquito and sandfly exposure
- Infrequently causes erythema, numbness, tingling, and rash

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Lindane

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- Lotion/creme benzene hexachloride
- Treat scabies
- Rare CNS toxicities (siezures) if accidentally ingested or absorbed through inflamed/excoriated skin

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Diethyltoluamide (DEET)

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- Insect repellant
- Used to prevent mosquito (malaria) and sand fly (leishmaniasis) diseases
- Can cause toxic encephalopathy in small children