FLAGELLATES The Intestinal and Genital Flagellates Objective Outline Intestinal and Genital Flagellates • The following species are found in humans • Enteromonas hominis • Retortamonas intestinalis • Chilomastix mesnili • Giardia lamblia • Trichomonas vaginalis • Trichomonas tenax • Trichomonas (Pentatrichomonas) hominis Giardia Lamblia (G.duodenalis or G.intestinalis) • Inhabits and reproduce in the upper portion of the small intestine, adhering to the intestinal epithelium with a prominent ventral adhesive disc • G. lamblia is responsible for the disease giardiasis TRANSMISSION: Fecal-oral route Life cycle of G. lamblia treatment • Metronidazole is the drug of choice for giardiasis in J.T.27. Metronidazole 250 mg three times daily for 7 days is as effective • as quinacrine in the treatment of giardiasis.27,36,80–83 Although • metronidazole has been reported to bemutagenic in bacteria and • carcinogenic at high dosages in animals,noevidence suggests that • it currently represents a risk in humans.80,81,83 • Quinacrine (Atabrine) administered 100 mg three times daily • for 5 days, with cure rates of 90% to 95%, was once considered • the drug of choice for giardiasis, but is no longer commercially • available; it can be obtained from PanoramaCompounding Pharmacy • (see Case 78-5, Question 2).27,80,81 • Furazolidone (Furoxone), an alternative to metronidazole, • is available as a tablet and suspension for the treatment of • giardiasis.27,80–83 Furazolidone has cure rates of 80% to 90%, • and the adult dosage is 100 mg four times daily for 7 days. • Furazolidone, which is available as a suspension, is preferred • by some clinicians for children. However, metronidazole should • be considered the drug of choice for giardiasis in both adults and • children. • Tinidazole (Tindamax), an analog of metronidazole, is also • highly effective for giardiasis.27,90 Other alternatives are paromomycin • (25–35 mg/kg/day in three divided doses for 7 days), • albendazole (400 mg daily for 5 days), and nitazoxanide (100– • 500 mg twice daily for 3–7 days).80,82,91–93 • After therapy, diarrhea usually subsides within 1 to 2 days • and completely resolves in about 10 days.80–83 Cyst excretion is • disrupted 2 days after initiation of therapy. Complete normalization • of intestinal functions, especially recovery from malabsorption, • may require 4 to 8 weeks.81 If J.T. does not respond to one • course of therapy, she may need a second course of metronidazole METRONIDAZOLE • Available for oral, intravenous, intravaginal and topical administration • The half life of metronidazole in plasma is approximately 8hrs • Metronidazole penetrates well into body tissues and fluids, including vaginal secretion, seminal fluid, saliva, breast milk and CSF except the placenta • After an oral dose >75% is eliminated in the urine largely as metabolites • Metronidazole is active against intestinal and extraintestinal cysts and trophozoites.
