GUANIDINE HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GUANIDINE HYDROCHLORIDE (GUANIDINE HYDROCHLORIDE).
Guanidine hydrochloride enhances the release of acetylcholine from nerve terminals and inhibits its reuptake, thereby increasing synaptic acetylcholine levels. It may also stabilize neuronal membranes and modulate ion channels.
| Metabolism | Guanidine is metabolized primarily in the liver via N-acetylation; approximately 90% of a dose is excreted unchanged in urine, with minor metabolism to inactive acetylated metabolites. |
| Excretion | Primarily renal (90-95% unchanged); minor biliary/fecal (<5%). |
| Half-life | 3-6 hours (prolonged in renal impairment; up to 24-48 hours in severe renal failure). |
| Protein binding | Minimal (<10%); not significantly bound to plasma proteins. |
| Volume of Distribution | Vd approximately 4-5 L/kg (extensive tissue distribution). |
| Bioavailability | Oral: 75-100% (well absorbed; food does not significantly affect). |
| Onset of Action | Oral: 2-4 hours (for myasthenic effect); IV: immediate but not used clinically. |
| Duration of Action | Oral: 4-8 hours; may extend in renal impairment. |
125 mg orally twice a day for 5-7 days, then 125 mg once daily for 3-6 weeks, or as directed for myasthenia gravis; alternatively, 15-40 mg/kg/day orally in 3-4 divided doses, not to exceed 1.5 g/day. Route: oral.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if CrCl < 10 mL/min. For CrCl 10-50 mL/min, reduce dose by 50% and extend interval to 24 hours. Not recommended in severe renal impairment. |
| Liver impairment | No specific guidelines available; use with caution in severe hepatic impairment due to potential for reduced clearance. Monitor for toxicity. |
| Pediatric use | 11-33 mg/kg/day orally in 3-4 divided doses, maximum 1 g/day. Safety and efficacy not established in children < 1 year. |
| Geriatric use | Initiate at lower end of dosing range (125 mg once daily) due to age-related renal function decline. Monitor renal function and for increased adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for GUANIDINE HYDROCHLORIDE (GUANIDINE HYDROCHLORIDE).
| Breastfeeding | Present in breast milk; M/P ratio unknown. Potential for infant toxicity (gastrointestinal, neuromuscular). Discontinue breastfeeding or drug. |
| Teratogenic Risk | Insufficient human data; animal studies not available. Based on mechanism, potential for fetal toxicity at high doses. Avoid in first trimester unless benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to guanidine or any component of the formulation","Severe renal impairment (CrCl <30 mL/min) without appropriate dose reduction","Preexisting bone marrow depression or blood dyscrasias","Patients with known QT prolongation or torsades de pointes risk"]
| Precautions | ["Bone marrow depression: May cause leukopenia, thrombocytopenia, and aplastic anemia; monitor CBCs regularly.","Renal impairment: Accumulation in renal failure increases toxicity; use with extreme caution and adjust dose.","Cardiotoxicity: Can induce arrhythmias, QT prolongation, and hypotension; monitor ECG and electrolytes.","Neurotoxicity: Potential for convulsions, confusion, and peripheral neuropathy, especially with high doses.","Gastrointestinal effects: Gastric irritation, nausea, and diarrhea are common; administer with food."] |
Loading safety data…
| Monitor maternal blood pressure, heart rate, ECG (QT interval), renal function. Fetal growth and amniotic fluid volume via ultrasound. Check for signs of neonatal hypotension or myasthenia if used near term. |
| Fertility Effects | No human data; animal studies not available. Theoretical risk of spermatogenesis impairment (based on structural analogs). |