Microsoft word - antiparasitics

GUIDELINE for TREATMENT of PARASITIC INFECTIONS

ROUNDWORMSBenzimidazoles (Mebendazole and Albendazole)
EXCEPT Strongyloides → Ivermectin FILARIAL WORMS Ivermectin
TAPEWORMS Praziquantel for adultworm stages
Albendazole for cysticercosis
FLUKES Praziquantel
May need to use Bithionol for some Fasciola infections LUMINAL (GI, GU) PROTOZOAMetronidazole

T. cruzi → Nifurtimox + Benznidazole
T. brucei spp. → Melarsoprol : begin treatment early in the disease course
Eflornithine : may be used for the CNS phase
TOXOPLASMA → Pyamethamine + Sulfamethoxazole or Metronidazole

MALARIA PROPYLAXIS
Chloroquine if traveling to areas with endemic chloroquine-sensitive
strains
Mefloquine if traveling to areas with chloroquine resistance
Doxycyline if traveling to regions with Mefloquine resistance
Chlorquanide (U.K only)
Primaquine to clear latent hepatic infection

ACUTE MALARIAChloroquine for P. ovale and P. malariae, as well as sensitive strains of P.
Quinine + Doxycycline for acute infection with CQ-resistant strains
Atovaquone + Chloruanide (Malarone) for acute infections
with CQ-resistant strains
High dose Mefliquone

ANTI-HELMINTHICS
GENERAL STRATEGY
Ascaris lumbircoides: mebendazole, pyrantel pamoate + albendazole Hookworm (Necator and Ancylostoma): restore hematologic status; drug therapy equivalent to Ascaris Whipworm (Tricuris): mebendazole, albendazole, axantel pamoate Strongyloides: ivermectin Enterobius: drug therapy equivalent to Ascaris Trichinosis: mebendazole, albendazole effective ONLY against early infection; corticosterioids to suppress reaction to chronic infection Filarial Worms (Wuchereria, Onchocerca): diethylcarbamazine, ivermectin Schistosoma: Praziquantel Clonorchis: Praziquantel Fasciola: Bithionol (available from CDC only) or triclabendazole Taenia saginata: praziquantel 4 mos. Taenia solium: praziquantel treats both adult worm infection and cystercercosis; albendazole treats cystercercosis Diphyllobothrium: praziquantel or niclosamide Echinococcus: long-term albendazole + surgical resection ALBENDAZOLE
CLASS: Benzimidazole
TX: broad spectrum against nematode infections
First-line therapy for roundworm, hookworm, pinworm, and whipworm
Also effective for cystic echinococcosis and Taenia solium cystercercosis
MECH: inhibits polymerization of worm β-tubulin
PHARM: The active metabolite (albendazole sulfoxide) has a high volume of
distribution → increased activity against deeply encysted organisms
Treatment usually only requires single dose
AR: low systemic toxicity; teratogenicity
CI: pregnant women, cirrhosis

MEBENDAZOLE
CLASS: Benzimidazole
TX: broad spectrum against nematode infections
First-line therapy for roundworm, hookworm, and whipworm
MECH: inhibits polymerization of worm β-tubulin
PHARM: Low oral biovailability due to non-absorption + first-pass metabolism
AR: low systemic toxicity; teratogenicity
CI: pregnancy women and peds < 2 yrs
IVERMECTIN
CLASS: Avermectin
TX: DOC for treatment of onchocerciasis
Effective against filarial worm infections (EXCECPT Loa Loa)
Also covers most nematodes (Strongyloides, Ascaris, whipworm, pinworm)
MECH: Increased conductance of Cl- through glutamate channels in nematodes
only
→ tonic paralysis of worm pharyngeal muscles
Not active against filarial stages
Cidal against developing larvae
Inhibits emergence of microfilariae from adult uterus → lowers organism load
in cutaneous vessels → reduce vector TMX of Onchocerca (black Tsetse fly)
PHARM: Long half-life due to slow clearance, large Vd, and enterohepatic
circulation
Treatment usually only requires single-dose
AR: low systemic toxicity; CNS toxicity may develop if there is damage to BBB
CI: pregnant women, cirrhosis
PRAZIQUANTEL
TX: DOC for cestode and trematode infections
First-line therapy for schistosomiasis
Fluke infections require higher dosages; tapeworm infections may be
eradicated with a single dose
MECH: Low-dose: increases worm muscular activity → spastic paralysis
High-dose: disruption of tegument → calcium influx → blebbing → PHARM: Inactivated by hepatic metabolism
AR: abdominal distress, headache, dizziness, sedation
CI: pregnant women
ANTI-PROTOZOAN AGENTS (NON-MALARIA)
GENERAL STRATEGY
Entamoeba histolytica: metronidazole is active against luminal and systemic infection Trcihomonas: metronidazole Giardia: metronidazole or tinidazole Cyclospora and Isospora : TMP-Sulfa T. cruzi: acute infection may be treated (limited efficacy) with nifertimox and benznidazole; long-term therapy limited by significant toxicity T. brucei : melasoprol for early infection, eflornathine for CNS disease Leishmania spp. : pentavalent antimony Toxoplasma: pyrimethamin + sulfadiazine; spiramycin if pregnant; metronidazole METRONIDAZOLE
TX: DOC for Trichomonas vaginitis, Giardia, and ALL forms of symptomatic
amebiasis
MECH: anaerobic bacteria + liver result in reduction of the nitro group, forming a
highly reactive radical → oxidative damage to DNA and proteins
PHARM: good distribution
AR: headache, dry mouth, metallic taste, anorexia, NVD, disulfuram-like reaction
with EtOH
CI: pregnant women in third trimester
ANTI-MALARIA AGENTS
GENERAL STRATEGY
Blood Szhizonticides: these agents terminate the circulating erythrocyte stage (clinical disease) of malaria Thus, they may be used for treatment of active disease and for chemoprophylaxis Tissue Schizonticides: these agnets act within hepatocytes to prevent the initial intra-hepatic schizogony that precedes active malarial disease Thus, the primary role of these drugs is in prophylaxis Gametocides and Sporontocides: activity against the sexual stages Not used clinically Could theoretically be active within infected mosquitoes (sporontocides) or prevent TMX of gametes during blood meal (gametocides) QUININE
CLASS: Blood schizonticide; quinolone ring derivative
TX: The DOC for chloroquine-resistant strains of malaria; no longer in widespread
use
MECH: Weak base → concentrates in food vacuole of Plasmodium → inhibits
polymerization of heme → increased toxicity to the organism
Free Heme generates ROSs (Fenton reaction) PHARM: nearly complete oral absorption AR Tinnitus, headaches, nausea, blurred vision Hypersensitivity: flushing, pruritis, hemolysis May develop ‘Balckwater Fever’ → massive intravascular hemolysis resulting in hemoglobinemia and renal failure Hypoglycemia due to increased insulin secretion Hypotonia due to decreased NMJ excitability CHLOROQUINE
CLASS: Blood schizonticide; quinolone ring derivative
TX: Used to terminate clinical malaria and for prophylaxis (suppressive)
MECH: Equivalent to QUININE
PHARM: high Vd, so dosing must be carefully titrated
AR: High doses cause hypotension, arrhythmias
> 5 g: may be lethal
CI: hepatic disease, G6PDH deficiency (will cause brisk hemolysis)
MEFLOQUINE
CLASS: Blood schizonticide; quinolone ring derivative
TX: DOC for prophylaxis in areas in which malaria is highly chloroquine-resistant
(This may be accomplished with weekly low doses)
High doses may be sued to treat CQ-resistant clinical disease
MECH: concentrates in food vacuoles but DOES NOT inhibit heme polymerizationl
instead, causes osmotic swelling
RES: resistance is rapidly evolving; usually associated with MDR malaria
PHARM: slow and incomplete absorption
AR: nausea, lassitude, dizziness, fatigue, seizures, psychosis
CI: pregnant women, Hx of psychosis
PRIMAQUINE
CLASS: Tissue Schizonticide; quinolone ring derivative
TX: DOC for clearance of latent hepatic schizonts (P. vivax and P. ovale)
Weak activity against P. falciparum hepatic schizonts
Significant gametocidal activity against all types of malaria
MECH: unknown; may be converted to an oxidative metabolite
RES: some resistance seen in P. vivax
PHARM: complete absorption with high Vd; rapidly converted to weak
metabolites
AR: hypotension (IM), methemoglobinemia
CI: G6PDH deficiency
CHLORGUANIDE (PROGUANIL)
CLASS: Tissue Schizonticide; quinolone ring derivative
TX: Malaria prophylaxis at the tissue schizont level
Also used to terminate clinical diseasewith co-formulated with atovaquone
(Malarone)
MECH: converted to CYCLOGUANIL → inhibits DHFR and parasitic DNA synthesis
RES: due to mutation at the drug binding site, decreasing affinity
PHARM: significant ethnic variation in generation of the active metabolite (CYP2C
conversion)
AR: no significant toxicity
ATOVAQUONE
CLASS: Hydroxynapthoquinone
TX: combined with Chlorquanide (as Malarone) for treatment of acute
chloroquine-resistant malaria
MECH: inhibits electron transport (ubiquinone analog)
PHARM: very low oral bioavailability; increased absorption with fatty meal
AR: maculopapular rash, fever, NVD, headache

Source: http://www.teasnag.org/wp-content/uploads/2012/03/Antiparasitics.pdf

Aug25g.pdf

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