DEFINITY RT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DEFINITY RT (DEFINITY RT).
Definity RT is a perflutren lipid microsphere suspension that acts as an ultrasound contrast agent. The microspheres consist of perfluoropropane gas encapsulated in a lipid shell. When administered intravenously, they oscillate in an ultrasound field, enhancing the backscatter of ultrasound waves, thereby improving visualization of cardiac chambers and blood flow.
| Metabolism | Perflutren (perfluoropropane) is inert and not metabolized. It is eliminated via the lungs in exhaled air. The lipid shell components are metabolized via normal lipid metabolic pathways. |
| Excretion | Primarily eliminated via the lungs as exhaled perfluoropropane gas; renal excretion of the lipid shell components is negligible (<1%). |
| Half-life | Terminal elimination half-life of perfluoropropane gas is approximately 1.3 minutes; clinical contrast enhancement persists for 3-5 minutes post-injection. |
| Protein binding | Negligible; perfluoropropane is not significantly bound to plasma proteins. |
| Volume of Distribution | Perfluoropropane: ~0.8 L/kg, reflecting distribution primarily into blood and well-perfused tissues; limited extravascular distribution due to gas phase. |
| Bioavailability | Intravenous: 100%. |
| Onset of Action | Intravenous: Immediate (within seconds) after bolus injection; left ventricular opacification appears within 10-20 seconds. |
| Duration of Action | Intravenous: Contrast enhancement lasts 3-5 minutes, sufficient for standard echocardiographic imaging; repeat doses may be administered as needed. |
10 µL/kg intravenously as a bolus injection; may repeat once after 30 minutes if needed.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for renal impairment; no data available for GFR-based modifications. |
| Liver impairment | No specific dose adjustments recommended for hepatic impairment based on Child-Pugh score. |
| Pediatric use | Safety and efficacy not established in pediatric patients; no dosing guidelines available. |
| Geriatric use | No specific dose adjustments recommended; use with caution due to potential for greater sensitivity in elderly patients. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DEFINITY RT (DEFINITY RT).
| Breastfeeding | It is unknown whether perflutren or its components are excreted in human milk. No M/P ratio is available. Caution should be exercised when administered to a nursing woman. Consider the developmental and health benefits of breastfeeding along with the mother's clinical need for Definity RT and any potential adverse effects on the breastfed infant. |
| Teratogenic Risk | Definity RT (perflutren lipid microsphere) is classified as FDA Pregnancy Category B. Animal studies in rats and rabbits at doses up to 40 and 20 times the human dose (based on body surface area) revealed no evidence of fetal harm. However, no adequate and well-controlled studies exist in pregnant women. Use during pregnancy only if clearly needed. First trimester risks are unknown; second and third trimester risks are not specifically identified but caution is advised. |
■ FDA Black Box Warning
WARNING: SERIOUS CARDIOPULMONARY REACTIONS: Serious cardiopulmonary reactions, including fatalities, have occurred during or within 30 minutes following the administration of DEFINITY RT. The risk is highest in patients with unstable cardiopulmonary conditions (e.g., acute myocardial infarction, acute coronary syndromes, worsening or unstable congestive heart failure, serious ventricular arrhythmias, respiratory failure, or recent cardiopulmonary surgery). Always have resuscitation equipment and trained personnel readily available.
| Serious Effects |
["Known or suspected hypersensitivity to perflutren or any component of the product.","Intracardiac right-to-left, bidirectional, or transient right-to-left shunts.","Patients with unstable cardiopulmonary conditions: acute myocardial infarction, acute coronary syndromes, worsening unstable congestive heart failure (NYHA Class III/IV), serious ventricular arrhythmias, respiratory failure, or recent cardiopulmonary surgery."]
| Precautions | ["Serious cardiopulmonary reactions: including fatalities, especially in patients with unstable cardiopulmonary conditions.","Hypersensitivity reactions: including anaphylaxis, have been reported.","Risk of embolic phenomena: Microspheres may cause microvascular obstruction in patients with right-to-left shunts, pulmonary hypertension, or severe pulmonary disease.","Use in patients with intracardiac shunts: Theoretical risk of cerebral microemboli."] |
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| Fetal Monitoring | During administration, monitor for hypersensitivity reactions, including anaphylaxis, and cardiopulmonary effects such as dyspnea, hypotension, or hypertension. Fetal heart rate monitoring should be considered during and after administration if clinically indicated. No specific maternal monitoring beyond standard clinical observation is required. |
| Fertility Effects | No studies have been conducted to assess the effect of Definity RT on fertility. Animal reproduction studies have not shown impairment of fertility at doses up to 40 times the human dose. No human data are available; theoretical effects on fertility are not established. |