Home Drug Guide Guanethidine Monosulfate

Drug Guide

Generic Name

Guanethidine Monosulfate

Brand Names Ismelin

Classification

Therapeutic: Antihypertensive; Sympatholytic agent

Pharmacological: Adrenergic neuron blokcer

FDA Approved Indications

  • Hypertension (primarily used in the past)

Mechanism of Action

Guanethidine inhibits the release of norepinephrine from sympathetic nerve endings, leading to vasodilation and decreased blood pressure.

Dosage and Administration

Adult: Initially, 20-50 mg daily in divided doses; dosage adjusted based on response and tolerability.

Pediatric: Not typically used in pediatric populations.

Geriatric: Start at lower doses; monitor closely for side effects.

Renal Impairment: Adjust dose as needed; renal function monitoring recommended.

Hepatic Impairment: No specific guidelines; use with caution.

Pharmacokinetics

Absorption: Moderate; 40-60% bioavailability after oral administration.

Distribution: Widely distributed; crosses the blood-brain barrier.

Metabolism: Minimal hepatic metabolism.

Excretion: Primarily renal excretion.

Half Life: Approximately 10-12 hours.

Contraindications

  • Known hypersensitivity to guanethidine
  • Severe cardiovascular disease

Precautions

  • Use with caution in patients with renal impairment, cerebrovascular disease, or bipolar disorder; may cause or exacerbate depression, orthostatic hypotension, and urinary retention.

Adverse Reactions - Common

  • Orthostatic hypotension (Frequent)
  • Diarrhea (Common)
  • Nasal congestion (Common)

Adverse Reactions - Serious

  • Severe hypotension (Rare)
  • Peripheral neuropathy with long-term use (Rare)
  • Psychiatric disturbances, depression (Rare)

Drug-Drug Interactions

  • Antihypertensive agents, especially other vasodilators or centrally acting agents.
  • MAO inhibitors may potentiate hypotensive effects.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor blood pressure, heart rate, mental status, and urinary output.

Diagnoses:

  • Risk for falls due to hypotension.
  • Impaired cardiac perfusion.

Implementation: Administer as prescribed; monitor for signs of hypotension and adverse effects.

Evaluation: Assess blood pressure response and symptom control; adjust dose accordingly.

Patient/Family Teaching

  • Rise slowly from sitting or lying position to minimize dizziness.
  • Report signs of depression, urinary retention, or severe hypotension.
  • Do not discontinue abruptly; follow dosing instructions carefully.

Special Considerations

Black Box Warnings:

  • Potential for severe hypotension leading to syncope.
  • Risk of hemolytic anemia with long-term therapy.

Genetic Factors: None specified.

Lab Test Interference: None known.

Overdose Management

Signs/Symptoms: Severe hypotension, dizziness, weakness, syncope.

Treatment: Supportive care; vasopressors may be used; also, gastric lavage and activated charcoal if ingestion was recent.

Storage and Handling

Storage: Store at room temperature, away from moisture and light.

Stability: Stable under recommended storage conditions.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.