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PYRANTEL

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Classification   |    Detailed evidence-based information

Substances Included Synonyms

Therapeutic Toxic Class

    A) Pyrantel, a pyrimidine derivative antihelmintic agent, is a depolarizing neuromuscular blocking agent that acts via the release of acetylcholine and inhibition of cholinesterase thereby causing the paralysis of susceptible helminths.

Specific Substances

    1) Pyrantel Pamoate
    2) Pyrantel Embonate
    3) Pirantel Pamoate
    4) CP-10423-16
    5) CAS 15686-83-6 (pyrantel)
    6) CAS 22204-24-6 (pyrantel embonate)

Available Forms Sources

    A) FORMS
    1) Pyrantel pamoate is available as 144 mg/mL oral suspension (Prod Info REESE'S PINWORM MEDICINE oral caplets, oral suspension, 2004).
    B) USES
    1) Pyrantel pamoate is indicated for the treatment of pinworms (enterobiasis) (Prod Info REESE'S PINWORM MEDICINE oral caplets, oral suspension, 2004).

Overview

Life Support

    A) This overview assumes that basic life support measures have been instituted.

Clinical Effects

    0.2.1) SUMMARY OF EXPOSURE
    A) WITH THERAPEUTIC USE
    1) The most commonly reported adverse effects, following therapeutic administration of pyrantel, include headache, dizziness, drowsiness, insomnia, rashes, anorexia, nausea, vomiting, abdominal pain, and diarrhea. Transient elevations of serum transaminase levels have been reported in a small percentage of patients.
    B) WITH POISONING/EXPOSURE
    1) There is no overdose information available at the time of this review.
    0.2.7) NEUROLOGIC
    A) WITH THERAPEUTIC USE
    1) Therapeutic use of pyrantel may cause headaches, drowsiness, restlessness, insomnia, and dizziness.
    0.2.8) GASTROINTESTINAL
    A) WITH THERAPEUTIC USE
    1) Gastrointestinal disturbances, including nausea, vomiting, diarrhea, abdominal pains, and anorexia, are commonly reported adverse effects following therapeutic administration of pyrantel.
    0.2.20) REPRODUCTIVE
    A) Pyrantel pamoate is classified as FDA pregnancy category C.
    B) There are no reports available of pyrantel being used by pregnant women. There has been no evidence of teratogenicity among rats or rabbits.

Laboratory Monitoring

    A) Serum drug levels are not clinically useful.
    B) Monitor liver enzyme levels in symptomatic patients.

Treatment Overview

    0.4.2) ORAL/PARENTERAL EXPOSURE
    A) ACTIVATED CHARCOAL: Administer charcoal as a slurry (240 mL water/30 g charcoal). Usual dose: 25 to 100 g in adults/adolescents, 25 to 50 g in children (1 to 12 years), and 1 g/kg in infants less than 1 year old.
    B) Treatment is SYMPTOMATIC and SUPPORTIVE.

Range Of Toxicity

    A) TOXICITY: The toxic dose in humans is not established.
    B) THERAPEUTIC DOSE: ORAL SUSPENSION: ADULTS AND CHILDREN 2 TO 12 YEARS OF AGE: A single oral dose of 11 mg/kg; maximum total dose: 1 g. Dosing is based on weight (dosage taken as a single dose): 25 to 37 pounds: 1/2 teaspoonful. 38 to 62 pounds: 1 teaspoonful. 63 to 87 pounds: 1.5 teaspoonfuls. 88 to 112 pounds: 2 teaspoonfuls. 113 to 137 pounds: 2.5 teaspoonfuls. 138 to 162 pounds: 3 teaspoonfuls. 163 to 187 pounds: 3.5 teaspoonfuls. 188 pounds and over: 4 teaspoonfuls. Safety and efficacy has not been established for children less than 25 pounds or under 2 years of age.

Clinical Effects

Summary Of Exposure

    A) WITH THERAPEUTIC USE
    1) The most commonly reported adverse effects, following therapeutic administration of pyrantel, include headache, dizziness, drowsiness, insomnia, rashes, anorexia, nausea, vomiting, abdominal pain, and diarrhea. Transient elevations of serum transaminase levels have been reported in a small percentage of patients.
    B) WITH POISONING/EXPOSURE
    1) There is no overdose information available at the time of this review.

Vital Signs

    3.3.3) TEMPERATURE
    A) HYPERTHERMIA
    1) WITH THERAPEUTIC USE
    a) Hyperthermia has been reported as an adverse effect following therapeutic administration of pyrantel pamoate (Cervoni & Oliver-Gonzalez, 1971; Anon, 1990).

Respiratory

    3.6.2) CLINICAL EFFECTS
    A) STRIDOR
    1) WITH THERAPEUTIC USE
    a) CASE REPORT - A 6-year-old female developed stridor and periorbital edema several hours after ingesting 250 mg of pyrantel pamoate suspension. The patient had no allergies or previous significant medical history other than a mild viremia that began several days earlier. The patient recovered following supportive treatment (Del Mar, 1982).

Neurologic

    3.7.1) SUMMARY
    A) WITH THERAPEUTIC USE
    1) Therapeutic use of pyrantel may cause headaches, drowsiness, restlessness, insomnia, and dizziness.
    3.7.2) CLINICAL EFFECTS
    A) HEADACHE
    1) WITH THERAPEUTIC USE
    a) Headaches may occur following therapeutic use of pyrantel (Prod Info Antiminth(R), pyrantel pamoate, 1974; Lenoir, 1985; Anon, 1990) Sweetman, 2002).
    b) During a study to determine the clinical efficacy of pyrantel in helminthiasis, headaches occurred in 6 of 158 patients following ingestion of a single dose of pyrantel pamoate (Cervoni & Oliver-Gonzalez, 1971).
    B) DROWSY
    1) WITH THERAPEUTIC USE
    a) Drowsiness may occur as an adverse effect following therapeutic use of pyrantel pamoate (Prod Info Antiminth(R), pyrantel pamoate, 1974; Cervoni & Oliver-Gonzalez, 1971) Sweetman, 2002).
    C) FEELING NERVOUS
    1) WITH THERAPEUTIC USE
    a) Restlessness occurred in two patients and irritability occurred in one patient after ingesting a single 50 mg/mL dose of a pyrantel pamoate suspension (Cervoni & Oliver-Gonzalez, 1971).
    D) INSOMNIA
    1) WITH THERAPEUTIC USE
    a) Insomnia has been reported as an adverse effect following therapeutic administration of pyrantel pamoate (Prod Info Antiminth(R), pyrantel pamoate, 1974; Cervoni & Oliver-Gonzalez, 1971) Sweetman, 2002).
    E) DIZZINESS
    1) WITH THERAPEUTIC USE
    a) Therapeutic use of pyrantel pamoate may cause dizziness (Prod Info Antiminth (R), 1974; Anon, 1984; (Anon, 1990) Sweetman, 2002).
    F) ASTHENIA
    1) WITH THERAPEUTIC USE
    a) A 72-year-old male with myasthenia gravis became fatigued while chewing and walking several hours after ingestion of a single 1000 mg dose of pyrantel pamoate (Bescansa et al, 1991). Pyrantel pamoate may worsen myasthenia gravis because of its actions as a depolarizing neuromuscular blocker.
    3.7.3) ANIMAL EFFECTS
    A) ANIMAL STUDIES
    1) PARALYSIS
    a) In rabbits, parenteral administration causes paralysis and death (Bescansa et al, 1991). Pyrantel exerts its antihelmintic effect by causing depolarizing neuromuscular blockade.

Gastrointestinal

    3.8.1) SUMMARY
    A) WITH THERAPEUTIC USE
    1) Gastrointestinal disturbances, including nausea, vomiting, diarrhea, abdominal pains, and anorexia, are commonly reported adverse effects following therapeutic administration of pyrantel.
    3.8.2) CLINICAL EFFECTS
    A) NAUSEA, VOMITING AND DIARRHEA
    1) WITH THERAPEUTIC USE
    a) Gastrointestinal distress, including nausea, vomiting, and diarrhea, may occur following therapeutic use of pyrantel pamoate and are transient effects (Prod Info Antiminth(R), pyrantel pamoate, 1974; Cervoni & Oliver-Gonzalez, 1971) Anon, 1984; (Anon, 1990; Lenoir, 1985) Sweetman, 2002).
    B) ABDOMINAL PAIN
    1) WITH THERAPEUTIC USE
    a) Abdominal pain and distension have been reported as adverse effects following therapeutic administration of pyrantel pamoate (Prod Info Antiminth(R), pyrantel pamoate, 1974; Cervoni & Oliver-Gonzalez, 1971) Anon, 1984; (Sarmah, 1988) Sweetman, 2002).
    C) LOSS OF APPETITE
    1) WITH THERAPEUTIC USE
    a) Anorexia may occur following therapeutic ingestion of pyrantel pamoate (Prod Info Antiminth(R), pyrantel pamoate, 1974; Cervoni & Oliver-Gonzalez, 1971) Anon, 1984; Sweetman, 2002).

Hepatic

    3.9.2) CLINICAL EFFECTS
    A) LIVER ENZYMES ABNORMAL
    1) WITH THERAPEUTIC USE
    a) Transient elevation of SGOT levels may occur following therapeutic use of pyrantel (Prod Info Antiminth, 1974; (McEvoy, 1997) Sweetman, 2002).

Dermatologic

    3.14.2) CLINICAL EFFECTS
    A) ERUPTION
    1) WITH THERAPEUTIC USE
    a) Skin rashes may occur following therapeutic ingestion of pyrantel pamoate (Prod Info Antiminth(R), pyrantel pamoate, 1974; Cervoni & Oliver-Gonzalez, 1971) Anon, 1984; (Anon, 1990) Sweetman, 2002).

Reproductive

    3.20.1) SUMMARY
    A) Pyrantel pamoate is classified as FDA pregnancy category C.
    B) There are no reports available of pyrantel being used by pregnant women. There has been no evidence of teratogenicity among rats or rabbits.
    3.20.2) TERATOGENICITY
    A) ANIMAL DATA
    1) There have been NO congenital defects or postnatal defects observed in pregnant rats after ingesting up to 3000 mg/kg or in pregnant rabbits after ingesting 1000 mg/kg (Briggs et al, 1998).
    3.20.3) EFFECTS IN PREGNANCY
    A) PREGNANCY CATEGORY
    PYRANTEL PAMOATEC
    Reference: Briggs et al, 1998
    3.20.4) EFFECTS DURING BREAST-FEEDING
    A) LACK OF INFORMATION
    1) There is lack of data available regarding the use of pyrantel during lactation (Briggs et al, 1998).

Laboratory Monitoring

Monitoring Parameters Levels

    4.1.1) SUMMARY
    A) Serum drug levels are not clinically useful.
    B) Monitor liver enzyme levels in symptomatic patients.

Treatment

Life Support

    A) Support respiratory and cardiovascular function.

Patient Disposition

    6.3.1) DISPOSITION/ORAL EXPOSURE
    6.3.1.5) OBSERVATION CRITERIA/ORAL
    A) Patients who exhibit only mild CNS depression or other signs of mild intoxication should be observed, either in the emergency department or as an inpatient, until no longer intoxicated.

Monitoring

    A) Serum drug levels are not clinically useful.
    B) Monitor liver enzyme levels in symptomatic patients.

Oral Exposure

    6.5.1) PREVENTION OF ABSORPTION/PREHOSPITAL
    A) ACTIVATED CHARCOAL
    1) PREHOSPITAL ACTIVATED CHARCOAL ADMINISTRATION
    a) Consider prehospital administration of activated charcoal as an aqueous slurry in patients with a potentially toxic ingestion who are awake and able to protect their airway. Activated charcoal is most effective when administered within one hour of ingestion. Administration in the prehospital setting has the potential to significantly decrease the time from toxin ingestion to activated charcoal administration, although it has not been shown to affect outcome (Alaspaa et al, 2005; Thakore & Murphy, 2002; Spiller & Rogers, 2002).
    1) In patients who are at risk for the abrupt onset of seizures or mental status depression, activated charcoal should not be administered in the prehospital setting, due to the risk of aspiration in the event of spontaneous emesis.
    2) The addition of flavoring agents (cola drinks, chocolate milk, cherry syrup) to activated charcoal improves the palatability for children and may facilitate successful administration (Guenther Skokan et al, 2001; Dagnone et al, 2002).
    2) CHARCOAL DOSE
    a) Use a minimum of 240 milliliters of water per 30 grams charcoal (FDA, 1985). Optimum dose not established; usual dose is 25 to 100 grams in adults and adolescents; 25 to 50 grams in children aged 1 to 12 years (or 0.5 to 1 gram/kilogram body weight) ; and 0.5 to 1 gram/kilogram in infants up to 1 year old (Chyka et al, 2005).
    1) Routine use of a cathartic with activated charcoal is NOT recommended as there is no evidence that cathartics reduce drug absorption and cathartics are known to cause adverse effects such as nausea, vomiting, abdominal cramps, electrolyte imbalances and occasionally hypotension (None Listed, 2004).
    b) ADVERSE EFFECTS/CONTRAINDICATIONS
    1) Complications: emesis, aspiration (Chyka et al, 2005). Aspiration may be complicated by acute respiratory failure, ARDS, bronchiolitis obliterans or chronic lung disease (Golej et al, 2001; Graff et al, 2002; Pollack et al, 1981; Harris & Filandrinos, 1993; Elliot et al, 1989; Rau et al, 1988; Golej et al, 2001; Graff et al, 2002). Refer to the ACTIVATED CHARCOAL/TREATMENT management for further information.
    2) Contraindications: unprotected airway (increases risk/severity of aspiration) , nonfunctioning gastrointestinal tract, uncontrolled vomiting, and ingestion of most hydrocarbons (Chyka et al, 2005).
    6.5.2) PREVENTION OF ABSORPTION
    A) ACTIVATED CHARCOAL
    1) CHARCOAL ADMINISTRATION
    a) Consider administration of activated charcoal after a potentially toxic ingestion (Chyka et al, 2005). Administer charcoal as an aqueous slurry; most effective when administered within one hour of ingestion.
    2) CHARCOAL DOSE
    a) Use a minimum of 240 milliliters of water per 30 grams charcoal (FDA, 1985). Optimum dose not established; usual dose is 25 to 100 grams in adults and adolescents; 25 to 50 grams in children aged 1 to 12 years (or 0.5 to 1 gram/kilogram body weight) ; and 0.5 to 1 gram/kilogram in infants up to 1 year old (Chyka et al, 2005).
    1) Routine use of a cathartic with activated charcoal is NOT recommended as there is no evidence that cathartics reduce drug absorption and cathartics are known to cause adverse effects such as nausea, vomiting, abdominal cramps, electrolyte imbalances and occasionally hypotension (None Listed, 2004).
    b) ADVERSE EFFECTS/CONTRAINDICATIONS
    1) Complications: emesis, aspiration (Chyka et al, 2005). Aspiration may be complicated by acute respiratory failure, ARDS, bronchiolitis obliterans or chronic lung disease (Golej et al, 2001; Graff et al, 2002; Pollack et al, 1981; Harris & Filandrinos, 1993; Elliot et al, 1989; Rau et al, 1988; Golej et al, 2001; Graff et al, 2002). Refer to the ACTIVATED CHARCOAL/TREATMENT management for further information.
    2) Contraindications: unprotected airway (increases risk/severity of aspiration) , nonfunctioning gastrointestinal tract, uncontrolled vomiting, and ingestion of most hydrocarbons (Chyka et al, 2005).
    6.5.3) TREATMENT
    A) SUPPORT
    1) There is no antidote for pyrantel overdose. Most patients may be safely managed with conservative, supportive care.

Range Of Toxicity

Summary

    A) TOXICITY: The toxic dose in humans is not established.
    B) THERAPEUTIC DOSE: ORAL SUSPENSION: ADULTS AND CHILDREN 2 TO 12 YEARS OF AGE: A single oral dose of 11 mg/kg; maximum total dose: 1 g. Dosing is based on weight (dosage taken as a single dose): 25 to 37 pounds: 1/2 teaspoonful. 38 to 62 pounds: 1 teaspoonful. 63 to 87 pounds: 1.5 teaspoonfuls. 88 to 112 pounds: 2 teaspoonfuls. 113 to 137 pounds: 2.5 teaspoonfuls. 138 to 162 pounds: 3 teaspoonfuls. 163 to 187 pounds: 3.5 teaspoonfuls. 188 pounds and over: 4 teaspoonfuls. Safety and efficacy has not been established for children less than 25 pounds or under 2 years of age.

Therapeutic Dose

    7.2.1) ADULT
    A) ORAL SUSPENSION: A single oral dose of 11 mg/kg of body weight should be administered up to a maximum total dose of 1 g (Prod Info REESE'S PINWORM MEDICINE oral caplets, oral suspension, 2004).
    7.2.2) PEDIATRIC
    A) ORAL SUSPENSION: CHILDREN 2 TO 12 YEARS OF AGE: A single dose of 11 mg/kg of body weight should be administered up to a maximum total dose of 1 g (Prod Info REESE'S PINWORM MEDICINE oral caplets, oral suspension, 2004).
    B) Dosing is based on weight (dosage taken as a single dose) (Prod Info REESE'S PINWORM MEDICINE oral caplets, oral suspension, 2004):
    1) 11 to 17 kg: 1/2 teaspoonful
    2) Greater than 17 to 28 kg: 1 teaspoonful
    3) 29 to 39 kg: 1.5 teaspoonfuls
    4) 40 to 51 kg: 2 teaspoonfuls
    5) Greater than 51 to 62 kg: 2.5 teaspoonfuls
    6) 63 to 73 kg: 3 teaspoonfuls
    7) 74 to 85 kg: 3.5 teaspoonfuls
    8) Greater than 85 kg: 4 teaspoonfuls
    C) Safety and efficacy have not been established in children less than 11 kg or under 2 years of age (Prod Info REESE'S PINWORM MEDICINE oral caplets, oral suspension, 2004).

Toxicity Information

    7.7.1) TOXICITY VALUES
    A) ANIMAL DATA
    1) LD50- (ORAL)MOUSE:
    a) 175 mg/kg (RTECS , 2002)
    2) LD50- (ORAL)RAT:
    a) 170 mg/kg (RTECS , 2002)

Pharmacology Toxicology

Pharmacologic Mechanism

    A) Pyrantel is a depolarizing neuromuscular blocking agent that induces persistent nicotinic activation, resulting in the spastic paralysis of the helminth. Pyrantel also inhibits cholinesterases (Hardman et al, 1996).

References

General Bibliography

    1) Alaspaa AO, Kuisma MJ, Hoppu K, et al: Out-of-hospital administration of activated charcoal by emergency medical services. Ann Emerg Med 2005; 45:207-12.
    2) Anon: Drugs for parasitic infections. Med Lett Drugs Ther 1990; 32:23-32.
    3) Bescansa E, Nicolas M, & Aguado C: Myasthenia gravis aggravated by pyrantel pamoate (letter). J Neurol Neurosurg & Psych 1991; 54:563.
    4) Briggs GG, Freeman RK, & Yaffe SJ: Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 5th ed, Williams & Wilkins, Baltimore, MD, 1998.
    5) Cervoni WA & Oliver-Gonzalez J: Clinical evaluation of pyrantel pamoate in helminthiasis. Am J Trop Med Hyg 1971; 20:589-591.
    6) Chyka PA, Seger D, Krenzelok EP, et al: Position paper: Single-dose activated charcoal. Clin Toxicol (Phila) 2005; 43(2):61-87.
    7) Dagnone D, Matsui D, & Rieder MJ: Assessment of the palatability of vehicles for activated charcoal in pediatric volunteers. Pediatr Emerg Care 2002; 18:19-21.
    8) Del Mar C: Angio-oedema after Combantrin in a six-year-old (letter). Med J Austr 1982; 2:117.
    9) Elliot CG, Colby TV, & Kelly TM: Charcoal lung. Bronchiolitis obliterans after aspiration of activated charcoal. Chest 1989; 96:672-674.
    10) FDA: Poison treatment drug product for over-the-counter human use; tentative final monograph. FDA: Fed Register 1985; 50:2244-2262.
    11) Golej J, Boigner H, Burda G, et al: Severe respiratory failure following charcoal application in a toddler. Resuscitation 2001; 49:315-318.
    12) Graff GR, Stark J, & Berkenbosch JW: Chronic lung disease after activated charcoal aspiration. Pediatrics 2002; 109:959-961.
    13) Guenther Skokan E, Junkins EP, & Corneli HM: Taste test: children rate flavoring agents used with activated charcoal. Arch Pediatr Adolesc Med 2001; 155:683-686.
    14) Hardman JG, Limbird LE, & Molinoff PB: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 9th ed, McGraw-Hill, New York, NY, 1996.
    15) Harris CR & Filandrinos D: Accidental administration of activated charcoal into the lung: aspiration by proxy. Ann Emerg Med 1993; 22:1470-1473.
    16) Hecht L & Murray WE: Theophylline-pyrantel pamoate interaction (letter). DICP, Ann Pharmacother 1989; 23:258.
    17) Lenoir G: Antiparasitic medications in children, neonates, and the fetus: pharmacokinetics, tolerance, toxicity. Arch Fr Pediatr 1985; 42:965-969.
    18) McEvoy GK: American Hospital Formulary Service 97, American Society of Health-System Pharmacists, Inc, Bethesda, MD, 1997.
    19) None Listed: Position paper: cathartics. J Toxicol Clin Toxicol 2004; 42(3):243-253.
    20) Pollack MM, Dunbar BS, & Holbrook PR: Aspiration of activated charcoal and gastric contents. Ann Emerg Med 1981; 10:528-529.
    21) Product Information: Antiminth(R), pyrantel pamoate. Pfizer Laboratories, New York, NY, 1988.
    22) Product Information: Antiminth(R), pyrantel pamoate. Roerig, a division of Pfizer Pharmaceuticals, New York, NY, 1974.
    23) Product Information: REESE'S PINWORM MEDICINE oral caplets, oral suspension, pyrantel pamoate oral caplets, oral suspension. Reese Pharmaceutical Company, Cleveland, Ohio, 2004.
    24) RTECS : Registry of Toxic Effects of Chemical Substances. National Institute for Occupational Safety and Health. Cincinnati, OH (Internet Version). Edition expires 8/31/2002; provided by Truven Health Analytics Inc., Greenwood Village, CO.
    25) Rau NR, Nagaraj MV, Prakash PS, et al: Fatal pulmonary aspiration of oral activated charcoal. Br Med J 1988; 297:918-919.
    26) Sarmah HC: A randomized controlled trial of pyrantel and mebendazole in children with enterobiasis and concomitant ascariasis. Indian Pediatr 1988; 25:544-547.
    27) Spiller HA & Rogers GC: Evaluation of administration of activated charcoal in the home. Pediatrics 2002; 108:E100.
    28) Thakore S & Murphy N: The potential role of prehospital administration of activated charcoal. Emerg Med J 2002; 19:63-65.