Skip to main content


Medically reviewed by Last updated on Sep 16, 2021.


(GWAHN i deen)

Index Terms

  • Guanidine HCl
  • Guanidine Hydrochloride

Dosage Forms

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

Tablet, Oral, as hydrochloride:

Generic: 125 mg

Pharmacologic Category

  • Cholinergic Agonist

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

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. Specifically, cholinergic effects may be enhanced or increased. 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

The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.

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

What is this drug used for?

• It is used to treat myasthenic syndrome of Eaton-Lambert.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Abdominal pain

• Flushing

• Sweating a lot

• Lack of appetite

• Nausea

• Diarrhea

• Abdominal cramps

• Dry mouth

• Anxiety

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Infection

• Bleeding like 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

• Kidney problems like 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

• Pinpoint red spots on skin

• Change in balance

• Tremors

• Confusion

• Mood changes

• Sensing things that seem real but are not

• Abnormal heartbeat

• Skin changes

• Fast heartbeat

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a limited summary of general information about the medicine's uses from the patient education leaflet and is not intended to be comprehensive. This limited summary does NOT include all information available about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not intended to provide medical advice, diagnosis or treatment and does not replace information you receive from the healthcare provider. For a more detailed summary of information about the risks and benefits of using this medicine, please speak with your healthcare provider and review the entire patient education leaflet.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.