Pyrantel (Oral-Local)


VA CLASSIFICATION
Primary: AP200{01}

Commonly used brand name(s): Combantrin; Pin-X; Reese"s Pinworm Caplets; Reese"s Pinworm Medicine.

Note: For a listing of dosage forms and brand names by country availability, see Dosage Forms section(s).



Category:


Anthelmintic (oral-local)—

Indications

Note: Bracketed information in the Indications section refers to uses that are not included in U.S. product labeling.

Accepted

[Ascariasis (treatment)]—Pyrantel is indicated in the treatment of ascariasis caused by Ascaris lumbricoides (common roundworm). {05} {06}{11}

Enterobiasis (treatment)—Pyrantel is indicated in the treatment of enterobiasis (oxyuriasis) caused by Enterobius vermicularis (Oxyuris vermicularis) (pinworm). {02} {05} {06}

[Helminth infections, multiple (treatment)]—Pyrantel is indicated in the treatment of multiple helminth infections.{11}

[Hookworm infection (treatment)]—Pyrantel is used in the treatment of hookworm infection (uncinariasis) caused by Ancylostoma duodenale (common hookworm; Old World hookworm) and Necator americanus (American hookworm; New World hookworm). {06} {07}

[Trichostrongyliasis (treatment)]—Pyrantel is used in the treatment of trichostrongyliasis caused by Trichostrongylus species. {07}{11}

—Not all species or strains of a particular helminth may be susceptible to pyrantel.


Pharmacology/Pharmacokinetics

Physicochemical characteristics:
Molecular weight—
    594.68

Mechanism of action/Effect:

Not vermicidal or ovicidal; acts as a depolarizing neuromuscular blocking agent, thereby causing sudden contraction, followed by paralysis, of the helminths; also acts as a cholinesterase inhibitor and ganglionic stimulant; helminths are rendered unable to maintain their position in the intestinal lumen and are expelled from the body in the fecal stream by peristalsis. {06}

Absorption:

Poorly and incompletely absorbed from gastrointestinal tract. {06}

Time to peak serum concentration

1 to 3 hours. {02}

Peak serum concentration:

0.05 to 0.13 mcg/mL. {02}

Elimination:
    Fecal (unchanged)—>50%. {02}
    Renal—<15% excreted in urine as unchanged drug and metabolites. {06}


Precautions to Consider

Pregnancy/Reproduction

Pregnancy—
Adequate and well-controlled studies in humans have not been done. {04}However, the use of pyrantel during pregnancy is not recommended.{11}{14}{15}{16}

Studies in animals have not shown that pyrantel causes adverse effects in the fetus. {02}

Breast-feeding

Pyrantel is poorly and incompletely absorbed from the gastrointestinal tract and resulting maternal serum concentrations are low (0.05 to 0.13 mcg/mL). Therefore, it is unlikely that significant amounts of pyrantel would be excreted in breast milk. Problems in humans have not been documented. However, the Canadian manufacturer recommends discontinuing breast-feeding while on pyrantel therapy.{11}

Pediatrics

Appropriate studies on the relationship of age to the effects of pyrantel have not been performed in children up to the age of 2.{14}{15}{16} However, no pediatrics-specific problems have been documented to date.


Geriatrics


No information is available on the relationship of age to the effects of pyrantel in geriatric patients.

Drug interactions and/or related problems
The following drug interactions and/or related problems have been selected on the basis of their potential clinical significance (possible mechanism in parentheses where appropriate)—not necessarily inclusive (» = major clinical significance):


Note: Combinations containing any of the following medications, depending on the amount present, may also interact with this medication.

» Piperazine {08}    (may antagonize the anthelmintic effects of pyrantel; concurrent use is not recommended)


Medical considerations/Contraindications
The medical considerations/contraindications included have been selected on the basis of their potential clinical significance (reasons given in parentheses where appropriate)— not necessarily inclusive (» = major clinical significance).


Risk-benefit should be considered when the following medical problem exists
Hypersensitivity to pyrantel
Liver disease{11}{14}{15}{16}
Note: Worsening of pre-existing myasthenia gravis has been reported in one patient.{12}



Patient monitoring
The following may be especially important in patient monitoring (other tests may be warranted in some patients, depending on condition; » = major clinical significance):


For pinworms
» Perianal examinations    (cellophane tape swabs of the perianal area to detect the presence of ova may be required prior to and starting 1 week following treatment with pyrantel, especially in patients with persisting symptoms; swabs should be taken every morning prior to defecation and bathing for at least 3 days to determine efficacy or provide proof of cure; perianal examinations may also be required to detect the presence of adult worms in the perianal area; no patient should be considered cured unless perianal swabs have been negative for 7 consecutive days)


For roundworms
» Stool examinations    (may be required prior to and approximately 2 weeks following treatment with pyrantel to determine efficacy or provide proof of cure; because of colonic mixing, ova may persist in the stool for up to 1 week following cure)




Side/Adverse Effects

Note: Side/adverse effects are generally infrequent at usual doses (11 mg [base] per kg of body weight [mg/kg]). However, they may be considerably more frequent at higher doses without any significant increase in efficacy of the medication.{11}

The following side/adverse effects have been selected on the basis of their potential clinical significance (possible signs and symptoms in parentheses where appropriate)—not necessarily inclusive:

Those indicating need for medical attention
Incidence rare {02}{11}
    
Hypersensitivity (skin rash)



Those indicating need for medical attention only if they continue or are bothersome
Incidence less frequent {02}{11}{14}{15}{16}
    
CNS effects (dizziness; drowsiness; headache; irritability; trouble in sleeping)
    
gastrointestinal disturbances (abdominal or stomach cramps or pain; diarrhea ; loss of appetite; nausea or vomiting)





Overdose
For more information on the management of overdose or unintentional ingestion, contact a poison control center (see Poison Control Center Listing).

Clinical effects of overdose
The following effects have been selected on the basis of their potential clinical significance (possible signs and symptoms in parentheses where appropriate)—not necessarily inclusive:
    
Autonomic dysfunction (blurred vision; confusion; dizziness, faintness, or lightheadedness when getting up from a lying or sitting position sudden ; sweating; unusual tiredness or weakness ; irregular heartbeat)
    
muscle spasm, twitches, and weakness
    
prostration ( extreme tiredness or weakness)
    
asphyxia (difficulty in breathing; loss of consciousness)
{11}

Treatment of overdose
There is no specific antidote for pyrantel overdose.{11}
To decrease absorption—Early gastric lavage. {11}

Supportive care—Maintaining an open airway and breathing, and maintaining blood pressure.{11}

Patients in whom intentional overdose is confirmed or suspected should be referred for psychiatric consultation.



Patient Consultation
As an aid to patient consultation, refer to Advice for the Patient, Pyrantel (Oral).

In providing consultation, consider emphasizing the following selected information (» = major clinical significance):

Before using this medication
»   Conditions affecting use, especially:
Hypersensitivity to pyrantel

Pregnancy—Use is not recommended





Breast-feeding—Use is not recommended
Other medications, especially piperazine

Proper use of this medication
No special preparations (e.g., dietary restrictions or fasting, concurrent medications, purging, or cleansing enemas) required before, during, or immediately after therapy

Proper administration technique for oral liquids

» Second dose may be required in some infections

For pinworms
Treating all household members concurrently; treating again in 2 to 3 weeks

» Proper dosing

» Proper storage

Precautions while using this medication
Checking with physician if no improvement within a few days

» Caution if dizziness or drowsiness occurs

For pinworms
» Avoiding scratching the anal area.

» Washing hands and fingernails with soap often during the day, especially before eating and after using the toilet.

Wearing tight underpants both day and night. Changing them daily.

Cleaning the bedroom floor by vacuuming or damp mopping for several days after treatment. Avoiding dry sweeping that may stir up dust.

Keeping the toilet seat clean

» Washing (not shaking) all bedding and nightclothes after treatment to prevent reinfection

Other measures may be recommended by some physicians

For hookworms
Importance of taking iron supplements daily during treatment and for up to 6 months following treatment if anemia was present prior to treatment


Side/adverse effects
Signs of potential side effects, especially hypersensitivity


General Dosing Information
No special preparations (e.g., dietary restrictions or fasting, concurrent medications, purging, or cleansing enemas) are required before, during, or immediately after treatment with pyrantel. {02}

Diet/Nutrition
Pyrantel may be taken with or without food at any time of day. It may be taken alone or with milk or fruit juice.{11}{14}{15}{16}

For hookworms
In the treatment of hookworms, especially in patients who are heavily infected or have inadequate dietary intake of iron, concurrent iron therapy may be required if anemia occurs. Iron therapy may need to be continued for up to 6 months to replenish iron stores.

For pinworms
Because of the high probability of transfer of pinworms, it is usually recommended that all members of the household be treated concurrently. Retreatment of entire household is recommended 2 to 3 weeks following initial treatment.


Oral Dosage Forms

Note: Bracketed uses in the Dosage Forms section refer to categories of use and/or indications that are not included in U.S. product labeling. The dosing and strengths of the dosage forms available are expressed in terms of pyrantel base (not the pamoate salt).

PYRANTEL PAMOATE ORAL SUSPENSION USP

Usual adult and adolescent dose {02} {06}{11}
[Ascariasis]
Oral, 11 mg (base) per kg of body weight as a single dose. May be repeated in two to three weeks if required.

Enterobiasis
Oral, 11 mg (base) per kg of body weight as a single dose. Repeat in two to three weeks.

[Hookworm infection]
Oral, 11 mg (base) per kg of body weight once a day for three days.

[Trichostrongyliasis]
Oral, 11 mg (base) per kg of body weight as a single dose.{11}


Usual adult prescribing limits
Up to 1 gram (base). {02}

Usual pediatric dose
[Ascariasis or]
Enterobiasis or
[ Uncinariasis (hookworm infection)]
Children 2 years of age and over— See Usual adult and adolescent dose.{11}{14}{15}{16}

Infants and children up to 2 years of age—Dosage has not been established.

Note: The following amounts have also been given— {03}In the U.S.



• Infants and children weighing:


• 11 to 16 kg (25 to 37 lb)—125 mg (base)


• 17 to 28 kg (38 to 62 lb)—250 mg (base)


• 29 to 39 kg (63 to 87 lb)—375 mg (base)


• 40 to 50 kg (88 to 112 lb)—500 mg (base)


• 51 to 62 kg (113 to 137 lb)—625 mg (base)


• 63 to 73 kg (138 to 162 lb)—750 mg (base)


• 74 to 84 kg (163 to 187 lb)—875 mg (base)


• > 85 kg (> 188 lb)—1000 mg (base){14}{15}{16}
In the treatment of enterobiasis, pyrantel may be given in the above amounts as a single dose. {14}{15}{16}In Canada



• Infants and children weighing:


• 11 kg or less (25 lb or less)—125 mg (base).


• 12 to 23 kg (26 to 50 lb)—250 mg (base).


• 24 to 45 kg (51 to 100 lb)—500 mg (base).


• 46 to 68 kg (101 to 150 lb)—750 mg (base).


• > 69 kg (> 151 lb)—1000 mg (base).{11}
In the treatment of ascariasis, enterobiasis, or uncinariasis (hookworm infection), pyrantel may be given in the above amounts as a single dose. Alternatively, in the treatment of uncinariasis, pyrantel may be given in the above amounts once a day for three days. {11}



Strength(s) usually available
U.S.—


250 mg (base) per 5 mL (OTC) [Reese"s Pinworm Medicine{05}] [Pin-X]

Canada—


250 mg (base) per 5 mL (OTC) [Combantrin{03} ( sodium benzoate) (tartrazine-free ) (imitation caramel flavor){11}]

Packaging and storage:
Store below 40 °C (104 °F), preferably between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Store in a tight, light-resistant container. Protect from freezing.

Auxiliary labeling:
   • Shake well.
   • May cause dizziness or drowsiness.
   • Continue medicine for full time of treatment (for 3-day uncinariasis treatment).

Note: When dispensing, include a calibrated liquid-measuring device.



PYRANTEL PAMOATE TABLETS

Usual adult and adolescent dose
See Pyrantel Pamoate Oral Suspension USP . {06}

Usual adult prescribing limits
See Pyrantel Pamoate Oral Suspension USP .

Usual pediatric dose
See Pyrantel Pamoate Oral Suspension USP .

Strength(s) usually available
U.S.—


62.5 mg (base) (OTC) [Reese"s Pinworm Caplets]

Canada—


125 mg (base) (OTC) [Combantrin (scored){03} ( tartrazine-free){11}]

Packaging and storage:
Store below 40 °C (104 °F), preferably between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Store in a tight, light-resistant container.

Auxiliary labeling:
   • May cause dizziness or drowsiness.
   • Continue medicine for full time of treatment (for 3-day uncinariasis treatment).



Revised: 3/16/2000



References
  1. USP DI 1989, VA Medication Classification System, p 2472.
  1. PDR 1989, Antiminth (Pfizer), p 1614.
  1. CPS 1988, Combantrin (Pfizer), p 185.
  1. Villar MA, Sibai BM. Nematode infections: is it wise to withhold medical treatment during pregnancy? Am J Obstet Gynecol 1992; 166: 549-50.
  1. PDR for Nonprescription Drugs 1990, Reese"s Pinworm Medicine (Reese), p 643.
  1. CPS 1989, Combantrin (Pfizer), p 224.
  1. Mandell, Douglas, Bennett (eds). Principles and practice of infectious diseases, 3rd ed. 1990. New York: Churchill Livingstone, p 418.
  1. Goodman and Gilman (eds). The pharmacologic basis of therapeutics, 7th ed, 1985. New York: Macmillan, p 1020.
  1. Product Information: Combantrin®, pyrantel pamoate, Pfizer Canada, Quebec, Canada. In: Krogh CME (ed): Compendium of Pharmaceuticals and Specialties, 34th ed. Canadian Pharmaceutical Association, Ottawa, Ontario, Canada, 1999:p.378–379.
  1. Bescansa E, Nicolas M, Aguado C et al: Myasthenia gravis aggravated by pyrantel pamoate. J Neurol Neurosurg Psychiatry 1991; 54:563.
  1. Product Information: Pin-X®, pyrantel pamoate, Effcon Laboratories, Marietta, GA, reviewed 2/2000.
  1. Product Information: Reese's Pinworm Medicine, pyrantel pamoate, Reese Pharmaceutical Company, Cleveland, OH, reviewed 3/2000.
  1. Product Information: Reese's Pinworm Caplets, pyrantel pamoate, Reese Pharmaceutical Company, Cleveland, OH, reviewed 3/2000.
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