can be mild, moderate or severe. Ascariasis is one of the commonest parasitic
infections. Other widely prevalent infections are toxoplasmosis, hookworm
disease and trichomoniasis.
infections can result in fetal or neonatal damage, cutaneous nodules, (a small
mass of tissue or aggregation of cells found on the skin), nutritional
deficiencies, skin eruptions, as well as major damage to eyes, lungs, heart,
central nervous system or liver.
Infections such as
schistosomiasis, leishmaniasis, amebiasis and trypanosomiasis are the pioneer
causes of mortality around the globe.
Joel Thome and Mary
Wen, both from the Washington State University College of Pharmacy, Washington,
reviewed literature on the prevalence of drug therapy for parasitic infections
in the United States. It was published in US Pharmacist 2012.
Owing to better
living, water, and food standards, people in the United States are less
affected by the parasitic infections. United States is naturally blessed with
protective climate particularly in the northern region. The citizens of America
are chiefly affected when traveling to the tropical regions, or when in direct
contact with immigrants or people newly immigrated to the U.S. Rarely the
infection is caused by direct contact with animals or pets and improperly cooked
Drug therapy and
prevention methods for common parasitic infections in the U.S. is described
This group of drugs is
chiefly used for treating and preventing malaria. The travelers are advised to
take two doses before entering malaria-endemic region and then continue for
four weeks after returning back.
can be taken for one week post returning.
The patients should be
educated about the importance of prevention of the bite of Anopheles mosquito.
can be achieved by wearing long-sleeved and long-legged clothing, using
mosquito nets and applying strong insect repellants.
Drugs such as
hydroxychloroquine and amodiaquine are rarely employed for monotherapy. However
they are sometimes used against chloroquine-resistant strains.
Metronidazole and Tinidazole:
tinidazole are the best available choice of treatment against amebiasis,
giardiasis and trichomoniasis. 'Drug therapy for amebiasis should generally
consist of a luminal agent that is capable of eradicating the luminal
(intestinal) infection' say the authors.
The recommended dose
of metronidazole is 750mg orally three times a day or 500mg intravenously every
6 hours for 10 days.
with chloroquine is effective for treating hepatic abcess or extraintestinal
Metronidazole in the
doses of 250mg three times a day with meals for five days is effective in
curing giardiasis. A single dose of 2g tinidazole also gives useful results.
Other options are nitazoxanide or paromomycin.
Metronidazole in the
single dose of 2g can treat trichomoniasis. Dyspepsia may be present with this
therapy so metronidazole 500mg twice daily can be given for seven days.
Although, less effective, tinidazole can also be given instead of
metronidazole is intended for bacterial vaginosis, and not Trichomonas vaginalis' caution the authors.
associated with nausea, dermatologic reactions, vaginal candida infection and
parageusia (bad taste in the mouth). Certain neurologic reactions such as
headache, dizziness, peripheral neuropathy, disorders of special senses (optic
or auditory nerve disorders), seizures, etc. are also seen.
Other side effects
associated with metronidazole are aseptic meningitis, leucopenia, hemolytic
uremic syndrome and encephalopathy.
Alcohol should be
avoided during this drug therapy so as not to risk a disulfiram-like reaction.
Ivermectin is the most
popular antiparasitic but not the most effective drug in the United States.
Although it is FDA approved for systemic infections by larval forms of Onchocerca volvulus and intestinal
strongyloidiasis (infected by small intestine roundworms), but it is widely
used for lice, scabies and enterobiasis (pinworms).
In southern Mexico and
Guatemala, ivermectin is extensively used for eradicating onchocerciasis (a
disease caused by black flies depositing larvae of Onchocerca volvulus under the skin).
Ivermectin works by
inactivating certain helminths (roundworms and tapeworms) through
hyperpolarizing their neurons ((making the parasite neurons more negatively
Ivermectin is normally
given as a single dose. Repeat doses might be required once or twice a year.
Side effects of
ivermectin include dizziness, fatigue, rash or abdominal pain. Other associated
effects can be lymphangitis, peripheral edema, myalgias, hypotension,
arthralgias, tachycardia and lymphadenitis.
Pyrantel pamoate is
used for curing enterobiasis, usually caused by pinworms (Enterobius vermicularis). Pyrantel pamoate is also used against
ascariasis and is employed as an alternative for mebendazole for hookworms.
Common adverse effects
of pyrantel pamoate are dizziness, somnolence and headache.
Albendazole is FDA
approved and as effective as mebendazole against helminth infestation. It is
highly effective in treating neurocysticercosis (tapeworm larvae invading the
central nervous system of humans) and echinococcosis (allergic reactions and
damage to organs by larva of tapeworm; infecting humans through contact with
dogs and livestock).
infections (e.g., ascariasis), the dose can be given on an empty stomach to
reduce absorption. For systemic or extraintestinal infections, albendazole can
be given with food to enhance absorption' recommend the authors.
Prolonged therapy of
albendazole is associated with deleterious side effects.
Adverse Effects of Antihelminthic Drugs:
The adverse effects of
antihelminthic drugs depend upon the duration of treatment. Some adverse
effects may occur when the parastic worms are dying rather than when they
directly infect humans.
Special Considerations When Treating Ocular or CNS
In the U.S. about 66
percent patients have seizures and are on antiseizure therapy. Globally
neurocysticercosis is the primary cause of symptomatic seizures.
'The use of a
glucocorticoid (e.g., prednisone) can greatly reduce morbidity when treating
certain CNS (central nervous system) manifestations of parasitic infections,
particularly certain forms of neurocysticercosis—cysticercal encephalitis,
subarachnoid neurocysticercosis, and spinal intramedullary cysticercosis.'
glucocorticoid with albendazole may reduce damaging inflammation at the site of
infectio, suggest the researchers.
An important point to
keep in mind is that 'Antiparasitic drug therapy is not always indicated for
CNS or intraocular infections because dying helminths may cause more damage
than live ones.'
not be used while treating ocular infections particularly with dexamethasone.
In case of CNS or eye infection, a neurologist or an ophthalmologist should be
consulted before the onset of the treatment.
Availability of Antiparasitic Drugs :
Most of the harmful
agents for curing parasitic infections are not used in the United States
because of low occurrence of infections.
Drugs not approved for
use in the U.S., may in some cases be procured from the CDC if it is on the
Investigational New Drug (IND) list with the FDA.
1. Drug Therapy for Common Parasitic Infections
Within the United States; Joel Thome et al; US Pharmacist 2012