Details About Overdose or Poisoning Generic Salt :: Phentolamine
Drug Pharmacology ::
I. Pharmacology. Phentolamineis a competitive presynaptic and postsynaptic alpha-adrenergic receptorblocker that produces peripheral vasodilation. By acting on both venousand arterial vessels, it decreases total peripheral resistance andvenous return. It also may stimulate beta-adrenergic receptors, causingcardiac stimulation. Phentolamine has a rapid onset of action (usually2 minutes) and a short duration of effect (approximately 15–20 minutes).
Drug Indications ::
Hypertensivecrisis associated with stimulant drug overdose (eg, amphetamines,cocaine, or ephedrine). Also an adjunct for cocaine-induced acutecoronary syndrome to reverse coronary artery vasoconstriction.
Hypertensivecrisis resulting from interaction between monoamine oxidase inhibitorsand tyramine or other sympathomimetic amines.
Hypertensive crisis associated with sudden withdrawal of sympatholytic antihypertensive drugs (eg, clonidine).
Extravasation of vasoconstrictive agents (eg, epinephrine, norepinephrine, and dopamine).
Drug Contra-Indications ::
III. Contraindications. Usewith extreme caution in patients with intracranial hemorrhage orischemic stroke; excessive lowering of blood pressure may aggravatebrain injury.
Drug Adverse Effects ::
IV. Adverse effects
Hypotension and tachycardia may occur from excessive doses.
Anginal chest pain and cardiac arrhythmias may occur.
Slow intravenous infusion (0.3 mg/min) may result in transient increased blood pressure caused by stimulation of beta-adrenergic receptors.
Use in pregnancy. Noassigned FDA category. However, this does not preclude its acute,short-term use in a seriously symptomatic patient (see Table III–1).
Drug Lab Interactions ::
Drug or laboratory interactions. Additiveor synergistic effects may occur with other antihypertensive agents,especially other alpha-adrenergic antagonists (eg, prazosin, terazosin).
Drug Dose Management ::
Dosage and method of administration
Parenteral. Give1–5 mg IV (children, 0.02–0.1 mg/kg) as a bolus; repeat at 5- to10-minute intervals as needed to lower blood pressure to a desiredlevel (usually 100 mm Hg diastolic in adults and 80 mm Hg diastolic inchildren, but this may vary with the clinical situation).
Catecholamine extravasation. Infiltrate5–10 mg in 10–15 mL of normal saline (children, 0.1–0.2 mg/kg; maximum10 mg) into an affected area with a fine (25- to 27-gauge) hypodermicneedle; improvement is evidenced by hyperemia and return to normaltemperature.
Drug Chemical Formulations ::
Parenteral. Phentolamine mesylate, 5 mg in 2-mL vials (with mannitol).
The suggested minimum stocking level to treat a 70-kg adult for the first 24 hours is 20 vials.