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Generic name: guanidine systemic

Brand names: Guanidine Hydrochloride

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, Oral, as hydrochloride:

Generic: 125 mg

Use: Labeled Indications

Reduction of the symptoms of muscle weakness associated with the myasthenic syndrome of Eaton-Lambert, not for myasthenia gravis


Hypersensitivity to guanidine or any component of the formulation

Dosage and Administration

Dosing: Adult

Eaton-Lambert syndrome: Oral: Initial: 10-15 mg/kg/day in 3-4 divided doses, gradually increase to 35 mg/kg/day, or up to development of side effects

Dosing: Geriatric

Refer to adult dosing.


Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).

Drug Interactions

Acetylcholinesterase Inhibitors: May enhance the adverse/toxic effect of Cholinergic Agonists. Monitor therapy

Beta-Blockers: May enhance the adverse/toxic effect of Cholinergic Agonists. Of particular concern are the potential for cardiac conduction abnormalities and bronchoconstriction. Monitor therapy

Cimetropium: Cholinergic Agonists may diminish the anticholinergic effect of Cimetropium. Monitor therapy

Sincalide: Drugs that Affect Gallbladder Function may diminish the therapeutic effect of Sincalide. Management: Consider discontinuing drugs that may affect gallbladder motility prior to the use of sincalide to stimulate gallbladder contraction. Consider therapy modification

Adverse Reactions

Frequency not defined.

Cardiovascular: Atrial fibrillation, cold extremities, flushing, hypotension, palpitations, tachycardia

Central nervous system: Ataxia, confusion, dizziness, emotional lability, hallucination, irritability, jitteriness, mood changes, nervousness, psychosis

Dermatologic: Diaphoresis, folliculitis, paresthesia, skin rash, xeroderma

Gastrointestinal: Abdominal cramps, anorexia, diarrhea, gastric irritation, nausea, sore throat, xerostomia

Genitourinary: Uremia

Hematologic & oncologic: Anemia, bone-marrow depression, bruise, leukopenia, petechia, purpura, thrombocytopenia

Hepatic: Abnormal hepatic function tests

Neuromuscular & skeletal: Tremor

Renal: Increased serum creatinine, interstitial nephritis (acute or chronic), renal tubular necrosis

Miscellaneous: Fever


Concerns related to adverse effects:

  • Bone marrow suppression: Dose-related, fatal bone marrow suppression had been reported with use. Avoid concurrent use with medications known to suppress bone marrow. Monitor closely; discontinue use if bone marrow suppression is suspected.

Disease-related concerns:

  • Renal impairment: Use with caution in patients with renal impairment.

Monitoring Parameters

CBC with differential (baseline and frequently thereafter); renal function (creatinine, BUN) and urinalysis (regularly)


Pregnancy Considerations

Animal reproduction studies have not been conducted.

Patient Education

  • Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
  • Patient may experience abdominal pain, flushing, sweating a lot, lack of appetite, nausea, diarrhea, abdominal cramps, or dry mouth. Have patient report immediately to prescriber signs of infection, signs of bleeding (vomiting blood or vomit that looks like coffee grounds; coughing up blood; blood in the urine; black, red, or tarry stools; bleeding from the gums; abnormal vaginal bleeding; bruises without a reason or that get bigger; or any severe or persistent bleeding), signs of kidney problems (unable to pass urine, blood in the urine, change in amount of urine passed, or weight gain), severe loss of strength and energy, behavioral changes, severe dizziness, passing out, burning or numbness feeling, cold sensation in arms or legs, anxiety, change in balance, tremors, confusion, mood changes, sensing things that seem real but are not, abnormal heartbeat, skin changes, or fast heartbeat (HCAHPS).
  • Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

Source: Wolters Kluwer Health. Last updated December 2, 2019.