VA Class:AP900

AHFS Class:

• Amebicides 8:30.04

Generic Name(s):

• Paromomycin Sulfate

Associated Monographs

• Aminoglycosides General Statement

Paromomycin is an aminoglycoside antibiotic with antibacterial and antiprotozoal activity.122

Amebiasis

Paromomycin sulfate is used as a luminal amebicide in the treatment of amebiasis caused by Entamoeba histolytica .100,110,116,117,118,122 A luminal amebicide generally is sufficient for the treatment of asymptomatic cyst passers who have only intraluminal infections; however, treatment of symptomatic intestinal amebiasis or extraintestinal disease involves the use of several drugs to ensure eradication of tissue-invading trophozoites as well as cysts in the intestinal lumen.100,116,117,118

Paromomycin is used alone for the treatment of asymptomatic intestinal amebiasis and is considered a drug of choice for the treatment of asymptomatic cyst passers, especially in children and pregnant women.100,110,116,117,118 Other luminal amebicides that can be used for the treatment of asymptomatic cyst passers include oral iodoquinol or diloxanide furoate (not commercially available in the US).100,110,116,117,118

Some strains of Entamoeba are nonpathogenic (e.g., E. dispar , E. hartmanni ) and asymptomatic intraluminal infections with these organisms generally do not require treatment.100,116,117,118 A high percentage of Entamoeba recovered from the intestinal tracts of homosexual males appear to be nonpathogenic.116,118 However, some of these nonpathogenic strains are difficult to differentiate from pathogenic E. histolytica without specialized testing.116,117 Because of the risk of invasive amebiasis if asymptomatic E. histolytica infections are not treated, many clinicians suggest that asymptomatic cyst passers in areas nonendemic for E. histolytica receive treatment with a luminal amebicide.116,117 Treatment of asymptomatic cyst passers in endemic areas (e.g., Mexico, India, Southern and Western Africa, Far East, portions of Central and South America) is more controversial.116,117,118

Although paromomycin may be effective for the treatment of mild intestinal amebiasis, the drug acts principally as a luminal amebicide and should not be used alone for the treatment of severe intestinal and extraintestinal amebiasis.117 The regimen of choice for symptomatic intestinal amebiasis or extraintestinal disease (including liver abscess) is treatment with a nitroimidazole derivative (oral metronidazole or oral tinidazole) followed by treatment with a luminal amebicide (oral iodoquinol or oral paromomycin).100,110,116,117,118 When used as follow-up after a tissue amebicide (e.g., metronidazole), paromomycin eradicates encysted E. histolytica in the intestinal lumen.116,117,118 Paromomycin may be preferred, rather than iodoquinol or diloxanide furoate, in children or pregnant women.116,117

Balantidiasis

Paromomycin has been used with some success for the treatment of balantidiasis† caused by Balantidium coli . However, tetracycline is considered the drug of choice and metronidazole and iodoquinol are alternatives for treatment of balantidiasis.100,110

Cestode (Tapeworm) Infections

Paromomycin has been used effectively for the treatment of cestodiasis (tapeworm infection) caused by certain cestodes pathogenic to humans including Diphyllobothrium latum † (fish tapeworm), Dipylidium caninum † (dog and cat tapeworm), Hymenolepis nana † (dwarf tapeworm), Taenia saginata † (beef tapeworm), and T. solium † (pork tapeworm). However, other agents (e.g., praziquantel, niclosamide [not commercially available in the US], nitazoxanide) currently are recommended for the treatment of these tapeworm infections.110

Cryptosporidiosis

Paromomycin reportedly has been beneficial in the treatment of cryptosporidiosis† caused by Cryptosporidium parvum in some patients with human immunodeficiency virus (HIV) infection.111,115,120 A regimen of paromomycin and azithromycin was used with some success (i.e., reduced oocyst excretion, improvement in diarrhea) in a limited number of patients with AIDS and cryptosporidiosis.120 However, results of a prospective, double-blind, placebo-controlled study in symptomatic HIV-infected individuals found that paromomycin (500 mg 4 times daily for 21 days) was no more effective than placebo for the treatment of cryptosporidiosis.107

The duration and severity of clinical symptoms of cryptosporidiosis vary depending on the immune status of the patient.114,126,127,128 Immunocompetent individuals usually have disease that is asymptomatic or self-limited (i.e., acute, watery diarrhea that persists for up to 2 weeks and may be accompanied by nausea, vomiting, abdominal pain, fever); however, immunocompromised individuals can have disease that manifests either as asymptomatic shedding of cryptosporidial oocysts or as transient infection with diarrhea lasting less than 2 months, chronic diarrhea lasting 2 months or longer with persistence of parasites in stool or biopsy specimens, or fulminant cholera-like illness.114,126,127,128 The severity of symptoms of cryptosporidiosis in HIV-infected individuals appears to depend on the CD4⁺ T-cell count, and fulminant infections usually have occurred in those with CD4⁺ T-cell counts less than 50/ mm³.114,126 No anti-infective agent has been found to reliably eradicate Cryptosporidium , although several drugs (e.g., paromomycin, azithromycin, nitazoxanide) appear to suppress the infection.114,126,127,128

The US Centers for Disease Control and Prevention (CDC), National Institutes of Health (NIH), and Infectious Diseases Society of America (IDSA), and other clinicians state that the most appropriate treatment for cryptosporidiosis in HIV-infected individuals is the use of potent antiretroviral agents and symptomatic treatment of diarrhea.114,126,127,128 A highly potent antiretroviral regimen can result in immune restoration (CD4⁺ T-cell counts exceeding 100/ mm³) which usually results in resolution of the infection.126,127,128 Symptomatic treatment of diarrhea in HIV-infected or immunocompetent individuals with cryptosporidiosis should include oral or IV fluids and electrolyte replacement to correct dehydration and nutritional supplementation when necessary;127,128 severe diarrhea may require intensive support.127 Adjunctive use of antimotility agents may be indicated, but these agents are not consistently effective and should be used with caution in young children.127,128

Dientamoeba fragilis Infections

Paromomycin is considered a drug of choice for the treatment of infections caused by Dientamoeba fragilis †.110 Iodoquinol, paromomycin, tetracycline, or metronidazole are the drugs of choice for the treatment of D. fragilis infections.110

Giardiasis

Paromomycin sulfate is considered an alternative for the treatment of giardiasis† caused by Giardia duodenalis (also known as G. lamblia or G. intestinalis ).100,110,119

Drugs of choice for the treatment of giardiasis are metronidazole, tinidazole, or nitazoxanide; alternative agents include paromomycin (especially in pregnant women), furazolidone (no longer commercially available in the US), or quinacrine (not commercially available in the US).100,110 Although paromomycin may be less effective than the other agents, the drug is poorly absorbed from the GI tract and may be useful for the treatment of giardiasis in pregnant women.100,110,119

Hepatic Encephalopathy

Paromomycin has been used in the management of hepatic coma122 as an adjunct to protein restriction and supportive therapy to inhibit nitrogen-forming bacteria of the GI tract. However, nonabsorbable disaccharides (lactulose) or certain other anti-infectives (neomycin or metronidazole) usually are recommended for such adjunctive therapy.123,124 (See Uses: Hepatic Encephalopathy in Neomycin Sulfate 8:12.02.)

Leishmaniasis

Cutaneous Leishmaniasis

Paromomycin sulfate has been used topically† (in conjunction with topical methylbenzethonium chloride) for the treatment of cutaneous leishmaniasis†.103,104,105,106,110,121,129 This topical regimen administered twice-daily for 10-20 days has been effective in some patients for the treatment of cutaneous leishmaniasis caused by Leishmania major †; however, topical paromomycin should be used only in geographic regions where cutaneous leishmaniasis species have low potential for mucosal spread.110,121,129

The treatment of choice for cutaneous leishmaniasis usually is pentavalent antimony compounds (IM or IV sodium stibogluconate or meglumine antimonate [drugs not commercially available in the US]);110,121,129 topical† paromomycin or IM or IV pentamidine are alternatives.110,121

Topical treatment cannot cure lymph node infection or protect against mucosal disease if metastasis has already started.121 Prolonged (e.g., twice daily for about 3 months) topical therapy has eliminated the protozoa from cutaneous lesions in patients with recurrent disease (leishmaniasis recidivans),103 and elimination of protozoa has occurred within 10-30 days of twice-daily therapy in patients with acute cutaneous leishmaniasis.104,105 If effective, clinical healing of lesions usually is complete within several weeks to a month after completion of topical paromomycin therapy.103,104,105

Visceral Leishmaniasis (Kala-azar)

Paromomycin sulfate has been used IM† for the treatment of visceral leishmaniasis (kala-azar).121,129,130

The treatment of choice for visceral leishmaniasis usually is pentavalent antimony compounds (e.g., IM or IV sodium stibogluconate or meglumine antimonate [drugs not commercially available in the US]) or IV amphotericin B (conventional or liposomal);110,121,129,130 IM or IV pentamidine or IM† paromomycin are alternatives.110

In an open-label, prospective, randomized study in patients 5-55 years of age with visceral leishmaniasis, IM† paromomycin (11 mg/kg daily for 21 days) was noninferior to IV amphotericin B (1 mg/kg of conventional amphotericin B every other day for 30 days).130 The final cure rate 6 months after the end of treatment was 95% in patients who received paromomycin and 99% in those who received amphotericin B.130

Other Uses

Paromomycin has been used for the treatment of acute bacillary dysentery†, carrier states of Shigella †, and gastroenteritis caused by Escherichia coli †, but other agents are preferred.

Administration

Paromomycin sulfate is administered orally with a meal.122

Paromomycin sulfate has been administered topically† for the treatment of cutaneous leishmaniasis† as a preparation containing paromomycin 15% and methylbenzethonium chloride 12% in white petrolatum.103,104,105,106,110,121,129 Paromomycin sulfate also has been administered IM† for the treatment of visceral leishmaniasis (kala azar)†.129,130 Topical and parenteral preparations of the drug are not commercially available in the US.

Dosage

Dosage of paromomycin sulfate is expressed in terms of paromomycin.122

Amebiasis Caused by Entamoeba histolytica

For the treatment of asymptomatic intestinal amebiasis caused by Entamoeba histolytica , the usual dosage of paromomycin in adults and children is 25-35 mg/kg daily, administered in 3 divided doses, for 5-10 days (usually 7 days).110,122

When paromomycin is used as follow-up after a tissue amebicide (e.g., metronidazole, tinidazole) in the treatment of mild to moderate or severe intestinal amebiasis or extraintestinal amebiasis (including hepatic abscess), the usual dosage in adults and children is 25-35 mg/kg daily, administered in 3 divided doses, for 5-10 days (usually 7 days).110,122

Cestode (Tapeworm) Infections

For the treatment of cestodiasis caused by Diphyllobothrium latum †, Dipylidium caninum †, Taenia saginata †, or T. solium †, a paromomycin dosage of 1 g every 15 minutes for 4 doses in adults and 11 mg/kg every 15 minutes for 4 doses in children has been used.125

For the treatment of cestodiasis caused by Hymenolepis nana †, a paromomycin dosage of 45 mg/kg daily, given as a single daily dose for 5-7 days, has been used in adults and children.125 Multiple-day therapy is necessary in H. nana infections, since the drug is not as effective against the larval stage of the worms as it is against adult worms. In addition, multiple worms are generally present in patients with H. nana infections. Patients with H. nana infections should be instructed to follow strict personal and environmental hygiene measures to avoid autoinfection with the parasite during therapy.

Cryptosporidiosis

For the treatment of cryptosporidiosis† in children, adolescents, or adults with human immunodeficiency virus (HIV) infection, the Centers for Disease Control and Prevention (CDC), National Institutes of Health (NIH), and Infectious Diseases Society of America (IDSA) recommend 25-35 mg/kg daily given in 2-4 divided doses.127,128 Maximum dosage in children is 500 mg 4 times daily.127,128

A paromomycin dosage of 1.5-2.25 g daily, given in 3-6 divided doses for 10-14 days, has been used;111,112,113 occasionally, more prolonged courses of therapy (e.g., 4-8 weeks) may be necessary.111 Prolonged maintenance therapy has been employed, although relapse still can occur during (e.g., after 3-4 months of paromomycin) such therapy.111

A regimen of paromomycin (1 g twice daily for 12 weeks) and azithromycin (600 mg once daily for 4 weeks) has been used for the treatment of cryptosporidiosis in a limited number of AIDS patients.120

Dientamoeba fragilis Infections

For the treatment of infections caused by Dientamoeba fragilis †, the usually recommended dosage of paromomycin for adult and pediatric patients is 25-35 mg/kg daily, administered in 3 divided doses, for 7 days.110

Giardiasis

For the treatment of giardiasis† caused by Giardia duodenalis (also known as G. lamblia or G. intestinalis ), a paromomycin dosage of 25-35 mg/kg daily, administered in 3 divided doses, for 7 days is recommended for adult and pediatric patients.110

Hepatic Encephalopathy

As an adjunct in the management of hepatic coma, the manufacturer states that adults can receive paromomycin in a dosage of 4 g daily in divided doses given for 5-6 days.122

Leishmaniasis

For the treatment of cutaneous leishmaniasis†, a preparation containing paromomycin sulfate 15% and methylbenzethonium chloride 12% in white petrolatum has been applied topically† twice daily for 10-20 days.103,104,105,106,110,121

For the treatment of visceral leishmaniasis† (kala azar), paromomycin has been administered IM† in a dosage of 11-20 mg/kg daily for 10-21 days.121,129,130

Adverse Effects

Adverse GI effects reported with oral paromomycin include anorexia, nausea,122 vomiting, epigastric burning and pain, increased GI motility, abdominal cramps,122 diarrhea,122 and pruritus ani. Paromomycin has also been reported to cause hypocholesterolemic and malabsorptive effects similar to those of neomycin. Malabsorption of xylose and sucrose, and abnormal fat metabolism have been demonstrated. Paromomycin may also cause steatorrhea by precipitation of bile salts.

Other adverse effects which have occasionally been reported with oral paromomycin include rash, headache, vertigo, eosinophilia, exanthema, and unexplained hematuria.

Following topical† application of paromomycin combined with topical methylbenzethonium chloride in patients with cutaneous leishmaniasis†, local reactions including burning,104,105,121 pruritus,121 erythema,129 pain,129 edema,129 and blisters121,129 have occurred.

Adverse effects reported following IM† injection of paromomycin in patients with visceral leishmaniasis† include injection site pain, fever, elevated liver enzymes, and reversible ototoxicity.130

Precautions and Contraindications

Paromomycin is contraindicated in patients with known hypersensitivity to the drug.122 Paromomycin also is contraindicated in patients with intestinal obstruction.122

As with other antibiotics, the use of paromomycin may result in the overgrowth of nonsusceptible organisms, including fungi, and patients should be carefully monitored for the development of new infections caused by nonsusceptible organisms.122 Secondary Staphylococcus enterocolitis may occur. Appropriate therapy should be instituted if a superinfection occurs.122

Like other aminoglycosides, paromomycin has potential nephrotoxic, ototoxic, and probably neuromuscular blocking effects. (See Cautions: Renal and Electrolyte Effects and Otic Effects in the Aminoglycosides General Statement 8:12.02.) Oral paromomycin should be administered with caution to patients with ulcerative intestinal lesions to avoid renal toxicity through inadvertent absorption of the drug.122 (See Cautions: Precautions and Contraindications in the Aminoglycosides General Statement 8:12.02.) High doses or prolonged therapy with paromomycin should be avoided.

Since paromomycin is only active against intestinal protozoa, the drug should not be used alone in the treatment of extraintestinal amebiasis.122

Mechanism of Action

Paromomycin sulfate is considered a luminal or contact amebicide since it acts principally in the intestinal lumen. Unlike tetracyclines, paromomycin is a direct-acting amebicide, and is effective either in the presence or absence of bacteria.

Like other aminoglycosides, paromomycin is bactericidal and appears to inhibit protein synthesis in susceptible bacteria at the 30S segment of the ribosome.

Spectrum

Paromomycin sulfate has a broad spectrum of activity, including activity against protozoa, bacteria, and cestodes.

Paromomycin sulfate is active against protozoa, especially Entamoeba histolytica. The drug is believed to act against both the trophozoite and encysted forms of Entamoeba . Limited in vitro studies indicate that paromomycin concentrations of 5 mcg/mL may be amebistatic and concentrations of 10 mcg/mL may be amebicidal against Acanthamoeba .101 In one study, several strains of Blastocystis hominis were not susceptible to the drug in vitro.108

Paromomycin has an antibacterial spectrum similar to that of neomycin.122 Paromomycin is active against some gram-positive bacteria (e.g., some strains of Staphylococcus ) and many gram-negative aerobic bacteria, but generally is inactive against Pseudomonas aeruginosa and anaerobic bacteria. Paromomycin also has some activity against Mycobacterium tuberculosis .

Paromomycin has been shown to be active against certain cestodes (tapeworms) pathogenic to humans including Diphyllobothrium latum (fish tapeworm), Dipylidium caninum (dog and cat tapeworm), Hymenolepis nana (dwarf tapeworm), Taenia saginata (beef tapeworm), and T. solium (pork tapeworm).

Pharmacokinetics

Absorption

Paromomycin sulfate is poorly absorbed from the GI tract, and most of an oral dose is excreted unchanged in feces.122 Impaired GI motility, or lesions or ulcerations of the intestine may facilitate absorption of the drug.

Paromomycin sulfate is rapidly absorbed following IM† injection, and peak plasma concentrations are attained within 1 hour.130

Distribution

Accumulation can occur in patients with impaired renal function.

Elimination

Almost 100% of an oral dose is eliminated unchanged in feces;122 any absorbed drug is slowly excreted in urine.

Chemistry and Stability

Chemistry

Paromomycin is an aminoglycoside antibiotic obtained from Streptomyces rimosus var. paromomycinus .122 The drug is structurally related to neomycin, streptomycin, and kanamycin.

Paromomycin sulfate occurs as a creamy white to light yellow, odorless or practically odorless, very hygroscopic, amorphous powder with a saline taste. The drug has solubilities of greater than 1 g/mL in water and less than 0.1 mg/mL in alcohol at 25°C.

Stability

Paromomycin sulfate capsules should be stored at 15-30°C and protected from moisture.122

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