eMedicine Specialties > Pediatrics: General Medicine > Parasitology
Amebiasis: Treatment & Medication
Updated: Aug 11, 2008
- Overview
- Differential Diagnoses & Workup
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Treatment
Medical Care
Asymptomatic infections are not treated in endemic areas. However, in nonendemic areas asymptomatic infection should be treated because of its potential to progress to invasive disease. Luminal agents that are minimally absorbed by the GI tract (eg, paromomycin, iodoquinol, diloxanide furoate) are best suited for such therapy.Metronidazole is the mainstay of therapy for invasive amebiasis. Tinidazole has been recently approved by the US Food and Drug Administration (FDA) for intestinal or extraintestinal amebiasis. Other nitroimidazoles with longer half-lives (ie, secnidazole, ornidazole) are currently unavailable in the United States . Nitroimidazole therapy leads to clinical response in approximately 90% of patients with mild-to-moderate amebic colitis. Chloroquine has also been used for patients with hepatic amebiasis. Dehydroemetine (available from the Centers for Disease Control and Prevention [CDC] Drug Services [404-639-3670]) has been successfully used but is not preferred due to its potential myocardial toxicity. For more information, see CDC Drug Service.
Intraluminal parasites are not affected by nitroimidazole therapy. Therefore, nitroimidazole therapy should be followed by treatment with a luminal agent such as paromomycin or diloxanide furoate to prevent a relapse. The recommended dose and the duration of therapy are described under the individual agents discussed in Medication.
Broad-spectrum antibiotics may be added to treat bacterial superinfection in a case of fulminant amebic colitis and suspected perforation. Bacterial coinfection of amebic liver abscess has occasionally been observed (both before and as a complication of drainage), and adding antibiotics to the treatment regimen is reasonable in the absence of a prompt response to nitroimidazole therapy.
Surgical Care
Surgical intervention is required for acute abdomen due to perforated amebic colitis, massive GI bleeding, or toxic megacolon. Toxic megacolon is rare and is typically associated with the use of corticosteroids. Surgical attempts to correct amebic bowel perforation or peritonitis should be avoided, although some patients may benefit from peritoneal lavage.
Unlike pyogenic liver abscess, amebic liver abscess generally responds to medical therapy alone and drainage is seldom necessary. When necessary, imaging-guided percutaneous treatment (needle aspiration or catheter drainage) has replaced surgical intervention as the procedure of choice for reducing the size of an abscess. The indications for drainage of amebic liver abscess include the following:
- Presence of left-lobe abscess (>10 cm in diameter)
- Impending rupture and abscess that does not respond to medical therapy within 3-5 days
Consultations
- Infectious disease specialist
- Gastroenterologist
- Surgeon
Diet
No special diet is recommended.
Medication
Antibiotics
Activity against anaerobic bacteria and protozoa is exhibited by several agents. Metronidazole is considered the drug of choice for symptomatic, invasive disease. Paromomycin is the drug of choice for noninvasive disease. Because parasites persist in the intestine of 40-60% of patients treated with metronidazole, follow it with paromomycin to cure luminal infection. Do not give the 2 medications at the same time because the diarrhea that often results from paromomycin might be confused with continuing active intestinal disease from the parasite.
Metronidazole (Flagyl, Protostat)
Kills trophozoites of E histolytica in intestine and tissue. Does not eradicate cysts from intestines.
Adult
Intestinal amebiasis:
PO: 500-750 mg PO tid for 5-10 d; alternatively, 2 g PO qd for 3 d or a single dose of 50 mg/kg
IV: 500 mg IV q6h for 5-10 d
Amebic liver abscess: 500 mg IV q6h for 10 d
Pediatric
35-50 mg/kg/d PO/IV divided q8h for 10 d
Metronidazole potentiates effect of warfarin; elimination is accelerated by simultaneous use of phenytoin and phenobarbital; clearance is decreased by cimetidine
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Avoid during first trimester of pregnancy; frequent adverse effects include nausea, anorexia, headache, and metallic taste; occasional adverse effects include vomiting, diarrhea, insomnia, weakness, dry mouth, stomatitis, vertigo, tinnitus, paresthesia, rash, dark urine, urethral burning, disulfiramlike reaction with alcohol, and candidiasis; rare adverse effects include seizures, pseudomembranous colitis, ataxia, leukopenia, peripheral neuropathy, pancreatitis, and encephalopathy
Tinidazole (Fasigyn, Tindamax)
5-nitroimidazole derivative with selective antimicrobial activity against anaerobic bacteria and protozoa. The mechanism by which tinidazole exhibits activity against Giardia and Entamoeba species is not known.
Adult
Intestinal amebiasis: 600 mg bid or 800 mg tid PO for 5 d; alternatively, 2 g PO qd for 3 d with food
Hepatic amebic abscess: 2 g PO qd for 3-5 d with food
Pediatric
<3 years: Not established
>3 years:
Intestinal amebiasis: 50 mg/kg/d PO for 3 d with food; not to exceed 2 g/dose
Amebic liver abscess: 50 mg/kg/d PO for 3-5 d with food; not to exceed 2 g/dose, limited data exist for pediatric patients treated >3 d (monitor closely)
Limited data available; interaction information based on experience with other nitroimidazole derivatives (ie, metronidazole); may prolong PT when coadministered with warfarin; avoid alcoholic beverages and preparations containing ethanol or propylene glycol during and 3 d following administration (may cause disulfiramlike reaction); may increase serum levels of lithium, phenytoin, cyclosporine, tacrolimus, and fluorouracil; CYP450 inducers (eg, phenobarbital, rifampin, phenytoin) may increase elimination; CYP450 inhibitors (eg, cimetidine, ketoconazole) may decrease elimination; concurrent administration with cholestyramine may decrease PO bioavailability; oxytetracycline may antagonize effect
Documented hypersensitivity; first trimester of pregnancy
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Carcinogenicity has been observed in mice and rats treated chronically with metronidazole (another nitroimidazole), although not observed with tinidazole, use cautiously; seizures and peripheral neuropathy have been reported; caution with history of blood dyscrasia; may cause metallic/bitter taste, nausea, anorexia, vomiting, weakness, fatigue, dizziness, or headache; if administered on day of hemodialysis, administer additional dose equivalent to one half of recommended dose following dialysis
Paromomycin (Humatin)
Amebicidal aminoglycoside antibiotic that is poorly absorbed. Active only against intraluminal form of amebiasis. Used to eradicate cysts of E histolytica following treatment with metronidazole or tinidazole for an invasive disease.
Adult
25-35 mg/kg/d PO divided q8h for 7 d
Pediatric
Administer as in adults
Nephrotoxic potential may increase with concurrent administration of other aminoglycosides, penicillins, cephalosporins, amphotericin B, or loop diuretics
Documented hypersensitivity; intestinal obstruction
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Due to narrow therapeutic index and toxic hazards associated with extended administration, do not use for long-term therapy; caution in renal failure, hypocalcemia, myasthenia gravis, and conditions that depress neuromuscular transmission; adjust dose in renal impairment
Anthelmintics
Parasite biochemical pathways are different from the human host; thus, toxicity is directed to the parasite, egg, or larvae.
Iodoquinol (Yodoxin)
Halogenated hydroxyquinoline. Luminal amebicide; acts primarily in bowel lumen because it is poorly absorbed. Best tolerated when given with meals. Because it is active only against intraluminal form of amebiasis, it is used to eradicate cysts of E histolytica after treatment of invasive disease.
Adult
650 mg PO tid for 20 d
Pediatric
30-40 mg/kg/d PO divided tid for 20 d; not to exceed 2 g/d
None reported
Documented hypersensitivity; iodine intolerance; impaired renal or liver function
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Occasional adverse effects include skin rash, acne, thyroid gland enlargement, nausea, diarrhea, cramps, and pruritus; rare adverse effects include optic neuritis, optic atrophy, loss of vision, peripheral neuropathy with prolonged use, and iodine sensitivity
Chloroquine phosphate (Aralen)
Inhibits growth by concentrating within acid vesicles of parasite, which increases internal pH of organism. Also inhibits hemoglobin utilization and metabolism of parasite. In vitro studies with trophozoites of E histolytica demonstrate that chloroquine possesses amebicidal activity comparable to that of emetine. Highly effective in treatment of amebic liver abscess when administered with emetine or dehydroemetine. Like emetine and dehydroemetine, it is not effective against luminal forms. Irreversible retinal damage does not occur with dose and duration used for treatment of hepatic amebiasis.
Adult
Hepatic amebiasis:
500 mg salt (300-mg base) PO bid for 2 d, followed by 250 mg salt (150-mg base) bid for 2-3 wk
Pediatric
Hepatic amebiasis: 10 mg (as base)/kg/d PO divided bid for 2-3 wk
Cimetidine may increase serum levels of chloroquine (possibly other 4-aminoquinolones); magnesium trisilicate may decrease absorption of 4-aminoquinolones
Documented hypersensitivity; psoriasis, retinal and visual field changes attributable to 4-aminoquinolones
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in hepatic disease, G-6-PD deficiency, psoriasis, porphyria; not recommended for long-term use in children; perform periodic ophthalmologic examinations; test for muscle weakness; retinopathy, tinnitus, nerve deafness, skin eruption, headache, anorexia, nausea, vomiting, and diarrhea may occur
Dehydroemetine (Mebadin)
Preferred over emetine because it is less toxic. Eradicates amebic tissue infections, including liver abscess, but does not act on luminal forms. Luminal amebicide also must be used to eradicate the bowel luminal infection. Only effective against the trophozoite forms and not the cyst form. Available in United States only from the Parasitic Disease Drug Service, CDC (Atlanta, GA 30333, [404-639-3670]). For more information, see CDC Drug Service.
Adult
1-1.5 mg/kg SC/IM qd for 8-10 d; not to exceed 90 mg/kg/d
Pediatric
1-1.5 mg/kg/d SC/IM divided bid for 8-10 d; not to exceed 90 mg/kg/d
None reported
Documented hypersensitivity; cardiac disease, renal disease, recent history of polyneuritis
Pregnancy
X - Contraindicated; benefit does not outweigh risk
Precautions
Caution in women who are pregnant and small children; hospitalize when administered because of the potential of serious cardiotoxicity and neuromuscular toxicity; monitor pulse and blood pressure at least tid; perform ECG prior to first injection, on day 5, day 10, and then weekly for 2 wk after last injection; discontinue if resting pulse >110 beats per min, marked hypotension, precordial pain, marked neuromuscular symptoms, T-wave depression, arrhythmias, or proteinuria occur
Diloxanide furoate (Furamid, Entamizole, Furamide)
Luminal amebicide; acts primarily in bowel lumen because it is poorly absorbed. Used to eradicate cysts of E histolytica after treatment of invasive disease. Not available in the United States.
Adult
500 mg PO tid for 10 d
Pediatric
20 mg/kg/d PO divided tid for 10 d; not to exceed 1500 mg/d
None reported
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Flatulence is common; nausea, vomiting, or diarrhea occasionally may be noted; rarely, diplopia, dizziness, or pruritus occurs
More on Amebiasis |
| Overview: Amebiasis |
| Differential Diagnoses & Workup: Amebiasis |
 Treatment & Medication: Amebiasis |
| Follow-up: Amebiasis |
| Multimedia: Amebiasis |
| References |
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Further Reading
Keywords
amebiasis, intestinal amebiasis, Entamoeba histolytica, E histolytica, Amoeba coli, A coli, amebic colitis, Entamoeba dispar, E dispar, dysentery, amebic dysentery, acute amebic colitis, fulminant amebic colitis, chronic amebic colitis, ameboma, amebic liver abscess, pleuropulmonary amebiasis, amebic peritonitis, amebic pericarditis, cerebral amebiasis, proctocolitis, dysentery, colitis, megacolon, ameboma, peritonitis, pericarditis, brain abscess, toxic megacolon, peritonitis, hepatic necrosis, portal venous obstruction, HIV, AIDS, diarrhea, bacterial dysentery, inflammatory bowel disease, carcinoma, tuberculosis, Crohn disease, actinomycosis, lymphoma, jaundice, fallopian tube amebiasis, ulcers, empyema, basilar atelectasis, pneumonia, lung abscess, heart failure
