Tolazoline
Mechanism :
An alpha-adrenergic blocking agent, tolazoline HCl is structurally related to phentolamine. By directly relaxing vascular smooth muscle, tolazoline has peripheral vasodilating effects and decreases total peripheral resistance. Tolazoline also is a competitive alpha1 and alpha2 adrenergic blocking agent.
Indication :
- Reduce pulmonary vascular resistance in newborn.
- Improve pulmonary circulation in ventilated babies.
Contraindications :
Cardiotoxic accumulation can occur quite rapidly in babies with renal failure when tolazoline is given by continuous infusion. Babies given a continuous tolazoline infusion must have their blood pressure measured periodically.
Dosing :
Loading dose IV:
1-2 mg/kg given over 10 minutes. Observe infant for 30 minutes. If a positive response occurs (increased pO2), commence maintenance therapy.
Maintenance dose IV infusion:
1-2 mg/kg/hour. Note: Correct acidosis and hypovolemia prior to administration, infuse through a scalp vein, pulmonary artery catheter, or right upper extremity vein, titrate dose to desired effect.
Doses >5 mg/kg/hour are not likely to increase efficacy. Titrate to discontinue.
Adverse Effect :
Transient tachycardia; peripheral vasodilatation presenting as sweating, hyperalgesia of the lips, piloerection; clear lacrimal and nasal discharge; muscle fasciculation; apprehensiveness. Adverse effects should diminish with time and generally disappear within 2 hours of dosing.
Interaction :
Norepinephrine, Epinephrine: A paradoxical drop in blood pressure can occur followed by a precipitous increase in blood pressure.
Alcohol: Accumulation of acetaldehyde can occur.
Hepatic Dose :
No dosage adjustments are recommended.