Considered a second line agent in the treatment of hypertension, usually with
Hypersensitivity to guanadrel or any component; known or suspected
pheochromocytoma; concurrent use or within 1 week of any monoamine oxidase
inhibitor; exacerbation of CHF
Orthostatic hypotension is common. Avoid using other drugs that cause
orthostatic hypotension (alpha-blocking agents or reserpine). Discontinue 48-72
hours before elective surgery (reduces potential for vascular collapse). If
emergency surgery required, notify anesthesiologist of the drug regimen. Avoid
using tricyclic antidepressants and indirect-acting sympathomimetics (can
reverse the blood pressure lowering effects). Use cautiously in asthma (may
aggravate condition), CHF (sodium and water retention), and PUD (may aggravate
condition). Safety and efficacy have not been established in pediatric patients.
Dosage adjustment required with renal dysfunction.
Cardiovascular: Palpitations (30%), chest pain (28%), peripheral edema (29%)
Central nervous system: Fatigue (64%), headache (58%), faintness (47% to
49%), drowsiness (45%), confusion (15%)
Gastrointestinal: Increased bowel movements (31%), gas pain (24% to 32%),
constipation (21%), anorexia (19%), weight gain/loss (42% to 44%)
Genitourinary: Nocturia (48%), polyuria (34%), ejaculation disturbances (18%)
Neuromuscular & skeletal: Paresthesia (25%), aching limbs (43%), leg
cramps (20% to 26%)
Ocular: Visual disturbances (29%)
Respiratory: Shortness of breath at rest (18%), coughing (27%)
1% to 10%:
Cardiovascular: Orthostatic hypotension
Central nervous system: Psychological problems (4%), depression (2%), sleep
Gastrointestinal: Glossitis (8%), nausea/vomiting (4%), xerostomia (2%)
Genitourinary: Impotence (5%)
Renal: Hematuria (2%)
<1% (Limited to important or life-threatening symptoms): Cardiovascular:
TCAs decrease hypotensive effect of guanadrel.
Increased toxicity of direct-acting amines (epinephrine, norepinephrine) by
guanadrel; the hypotensive effect of guanadrel may be potentiated.
Increased effect of beta-blockers, vasodilators.
Phenothiazines may inhibit the antihypertensive response to guanadrel;
consider an alternative antihypertensive with different mechanism of action.
Amphetamines, related sympathomimetics, and methylphenidate decrease the
antihypertensive response to guanadrel; consider an alternative antihypertensive
with different mechanism of action. Reassess the need for amphetamine, related
sympathomimetic, or methylphenidate; consider alternatives.
Ephedrine may inhibit the antihypertensive response to quanadrel; consider an
alternative antihypertensive with different mechanism of action. Reassess the
need for ephedrine.
Norepinephrine/phenylephrine have exaggerated pressor response; monitor blood
MAO inhibitors may cause severe hypertension; give at least 1 week apart.
Acts as a false neurotransmitter that blocks the adrenergic actions of
norepinephrine; it displaces norepinephrine from its presynaptic storage
granules and thus exposes it to degradation; it thereby produces a reduction in
total peripheral resistance and, therefore, blood pressure
Peak effect: Within 4-6 hours
Duration: 4-14 hours
Absorption: Oral: Rapid
Serum half-life, biphasic:
Initial: 1-4 hours
Terminal: 5-45 hours
Time to peak serum concentration: Within 1.5-2 hour
Elderly: Initial: 5 mg once daily
Dosing interval in renal impairment:
Clcr 10-50 mL/minute: Administer every 12-24 hours.
Clcr <10 mL/minute: Administer every 24-48 hours.
Use is limited to second-line therapy in the treatment of
|Mental Health: Effects
on Mental Status|
Sedation is common; may cause confusion; may rarely cause
Effects on Psychiatric
Contraindicated with MAOIs; TCAs and phenothiazines may decrease the
hypotensive effects of guanadrel
|Dental Health: Local
Manufacturer's information states that guanadrel may block vasopressor
activity of epinephrine. This has not been observed during use of epinephrine as
a vasoconstrictor in local anesthesia.
Effects on Dental Treatment|
No effects or complications reported
May cause orthostatic hypotension, sit or lie down at the first sign of
dizziness or weakness; rise slowly from sitting or lying, especially for
prolonged periods; take no new prescription or OTC medication without contacting
your physician or pharmacist
Monitor blood pressure, standing and sitting/supine
Tablet, as sulfate: 10 mg, 25 mg
Finnerty FA Jr and Brogden RN,
"Guanadrel: A Review of Its Pharmacodynamic and Pharmacokinetic Properties and Therapeutic Use in Hypertension,"
Drugs, 1985, 30(1):22-31.
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