DOPAMINE HCL
Chemistry - An endogenous catecholamine which is the immediate precursor to norepinephrine, dopamine (as the HCl salt) occurs as a white to off-white crystalline powder. It is freely soluble inwater and soluble in alcohol. The injectable concentrated solution has a pH of 2.5 - 5.5 and maycontain an antioxidant (sodium bisulfate). The pH of the ready-to-use injectable products indextrose have a pH from 3 - 5.
Solutions that are pink, yellow, brown or purple indicate decomposition of the drug. Solutions thatare darker than a light yellow should be discarded. Dopamine solutions should be stored at roomtemperature (15-30°C).
After dilution in a common IV solution (not 5% bicarbonate), dopamine is stable for at least 24hours at room temperature, but it is recommended to dilute the drug just prior to use. Dopamine isstable in solutions with a pH of less than 6.4, and most stable at pH's less than 5. It is oxidized atalkaline pH.
Dopamine is reported to be compatible with the following IV fluids: D5 in LRS, D5 in half-normal saline, D5 in normal saline, D5W, mannitol 20% in water, lactated Ringer's, normal saline, and 1/6M sodium lactate. Dopamine is reported to be compatible with the following drugs: aminophylline, bretylium tosylate, calcium chloride, carbenicillin disodium, cephalothin sodium neutral, chloramphenicol sodium succinate, dobutamine HCl, gentamicin sulfate (gentamicin potency retained for only 6 hours), heparin sodium, hydrocortisone sodium succinate, kanamycinsulfate, lidocaine HCl, methylprednisolone sodium succinate, oxacillin sodium, potassium chloride, tetracycline HCl, and verapamil HCl.
Dopamine is reported to be incompatible with: Amphotericin B, ampicillin sodium, iron salts, metronidazole w/sodium bicarbonate, penicillin G potassium, and sodium bicarbonate.
Compatibility is dependent upon factors such as pH, concentration, temperature, and diluents used and it is suggested to consult specialized references for more specific information.
At very low IV doses, 0.5 - 2 micrograms/kg/min, dopamine acts predominantly on dopaminergicreceptors and dilates the renal, mesenteric, coronary, and intracerebral vascular beds. At doses from2 - 10 micrograms/kg/min, dopamine also stimulates beta1 adrenergic receptors. The net effect atthis dosage range is to exert positive cardiac inotropic activity, increase organ perfusion, renal bloodflow and urine production. At these lower doses, systemic vascular resistance remains largelyunchanged. At higher doses, >10-12 micrograms/kg/min, the dopaminergic effects are overriddenby alpha effects. Systemic peripheral resistance is increased and hypotension may be corrected incases where systemic vascular resistance is diminished. Renal and peripheral blood flow are thusdecreased.
Uses, Indications - Dopamine should be used only in critical care settings where adequate monitoring can be provided. It is used to correct the hemodynamic imbalances present in shock afteradequate fluid volume replacement, to treat oliguric renal failure, and, occasionally, as adjunctivetherapy for the treatment of acute heart failure.
Dopamine is widely distributed in the body, but does not cross the blood-brain barrier in appreciable quantities. It is unknown if dopamine crosses the placenta.
The plasma half-life of dopamine is approximately 2 minutes. It is metabolized in the kidney, liver, and plasma by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) to inactivecompounds. Up to 25% of a dose of dopamine is metabolized to norepinephrine in the adrenergicnerve terminals. In human patients receiving monoamine oxidase inhibitors, dopamine's duration ofactivity can be as long as one hour.
Contraindications/Precautions - Dopamine is contraindicated in patients with pheochromocytoma, ventricular fibrillation, and uncorrected tachyarrhythmias. It is not a substitute for adequatefluid, electrolyte or blood product replacement therapy and should be used with caution in patientswith ischemic heart disease or an occlusive vascular disease. Decrease dose or discontinue the drugshould symptoms occur implicating dopamine as the cause of reduced circulation to the extremitiesor the heart. The drug should be discontinued or dosage reduced should arrhythmias (PVC's)occur.
Extravasation injuries with dopamine can be very serious with necrosis and sloughing of surrounding tissue. patient's IV sites should be routinely monitored. Should extravasation occur, infiltrate the site (ischemic areas) with a solution of 5-10 mg phentolamine (Regitine®) in 10-15 ml of normal saline. A syringe with a fine needle should be used to infiltrate the site with many injections.
Overdosage - Accidental overdosage is manifested by excessive blood pressure elevation (see adverse effects above). Treatment consists only of temporarily discontinuing therapy since dopamine's duration of activity is so brief. Should the patients condition fail to stabilize, the use of phentolamine has been suggested for use.
Dopamine may reverse the effects of beta-blocking agents.
Monoamine oxidase inhibitors (rarely used in veterinary medicine), can significantly prolongand enhance the effects on dopamine.
Use of halothane or cyclopropane may result in increased myocardial sensitization to the catecholamines; dopamine-induced ventricular arrhythmias may be treated with propranolol.
Seizures, hypotension, and bradycardia have been reported if dopamine is used concurrently withphenytoin.
In animals (species not specified), the renal and mesenteric vasodilitation effects of dopamine havebeen antagonized by butyrephenones (e.g., haloperidol), opiates, and phenothiazines.
Storage, Stability, Compatibility
Dopamine injectable products should be protected from light.Solutions that are pink, yellow, brown or purple indicate decomposition of the drug. Solutions thatare darker than a light yellow should be discarded. Dopamine solutions should be stored at roomtemperature (15-30°C).
After dilution in a common IV solution (not 5% bicarbonate), dopamine is stable for at least 24hours at room temperature, but it is recommended to dilute the drug just prior to use. Dopamine isstable in solutions with a pH of less than 6.4, and most stable at pH's less than 5. It is oxidized atalkaline pH.
Dopamine is reported to be compatible with the following IV fluids: D5 in LRS, D5 in half-normal saline, D5 in normal saline, D5W, mannitol 20% in water, lactated Ringer's, normal saline, and 1/6M sodium lactate. Dopamine is reported to be compatible with the following drugs: aminophylline, bretylium tosylate, calcium chloride, carbenicillin disodium, cephalothin sodium neutral, chloramphenicol sodium succinate, dobutamine HCl, gentamicin sulfate (gentamicin potency retained for only 6 hours), heparin sodium, hydrocortisone sodium succinate, kanamycinsulfate, lidocaine HCl, methylprednisolone sodium succinate, oxacillin sodium, potassium chloride, tetracycline HCl, and verapamil HCl.
Dopamine is reported to be incompatible with: Amphotericin B, ampicillin sodium, iron salts, metronidazole w/sodium bicarbonate, penicillin G potassium, and sodium bicarbonate.
Compatibility is dependent upon factors such as pH, concentration, temperature, and diluents used and it is suggested to consult specialized references for more specific information.
Pharmacology - DOPAMINE HCL
Dopamine is a precursor to norepinephrine and acts directly and indirectly (byreleasing norepinephrine) on both alpha and beta1 receptors. Dopamine also has dopaminergiceffects.At very low IV doses, 0.5 - 2 micrograms/kg/min, dopamine acts predominantly on dopaminergicreceptors and dilates the renal, mesenteric, coronary, and intracerebral vascular beds. At doses from2 - 10 micrograms/kg/min, dopamine also stimulates beta1 adrenergic receptors. The net effect atthis dosage range is to exert positive cardiac inotropic activity, increase organ perfusion, renal bloodflow and urine production. At these lower doses, systemic vascular resistance remains largelyunchanged. At higher doses, >10-12 micrograms/kg/min, the dopaminergic effects are overriddenby alpha effects. Systemic peripheral resistance is increased and hypotension may be corrected incases where systemic vascular resistance is diminished. Renal and peripheral blood flow are thusdecreased.
Uses, Indications - Dopamine should be used only in critical care settings where adequate monitoring can be provided. It is used to correct the hemodynamic imbalances present in shock afteradequate fluid volume replacement, to treat oliguric renal failure, and, occasionally, as adjunctivetherapy for the treatment of acute heart failure.
Pharmacokinetics - DOPAMINE HCL
Dopamine is not administered orally as it is rapidly metabolized in the GItract. After IV administration, the onset of action is usually within 5 minutes and persists for lessthan 10 minutes after the infusion has stopped.Dopamine is widely distributed in the body, but does not cross the blood-brain barrier in appreciable quantities. It is unknown if dopamine crosses the placenta.
The plasma half-life of dopamine is approximately 2 minutes. It is metabolized in the kidney, liver, and plasma by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) to inactivecompounds. Up to 25% of a dose of dopamine is metabolized to norepinephrine in the adrenergicnerve terminals. In human patients receiving monoamine oxidase inhibitors, dopamine's duration ofactivity can be as long as one hour.
Contraindications/Precautions - Dopamine is contraindicated in patients with pheochromocytoma, ventricular fibrillation, and uncorrected tachyarrhythmias. It is not a substitute for adequatefluid, electrolyte or blood product replacement therapy and should be used with caution in patientswith ischemic heart disease or an occlusive vascular disease. Decrease dose or discontinue the drugshould symptoms occur implicating dopamine as the cause of reduced circulation to the extremitiesor the heart. The drug should be discontinued or dosage reduced should arrhythmias (PVC's)occur.
Adverse Effects, Warnings
Most frequent adverse effects seen include nausea and vomiting, ectopic beats, tachycardia, palpitation, hypotension, hypertension, dyspnea, headache and vasoconstriction.Extravasation injuries with dopamine can be very serious with necrosis and sloughing of surrounding tissue. patient's IV sites should be routinely monitored. Should extravasation occur, infiltrate the site (ischemic areas) with a solution of 5-10 mg phentolamine (Regitine®) in 10-15 ml of normal saline. A syringe with a fine needle should be used to infiltrate the site with many injections.
Overdosage - Accidental overdosage is manifested by excessive blood pressure elevation (see adverse effects above). Treatment consists only of temporarily discontinuing therapy since dopamine's duration of activity is so brief. Should the patients condition fail to stabilize, the use of phentolamine has been suggested for use.
Drug Interactions
Oxytocic drugs may cause severe hypertension when used with dopamine.Dopamine may reverse the effects of beta-blocking agents.
Monoamine oxidase inhibitors (rarely used in veterinary medicine), can significantly prolongand enhance the effects on dopamine.
Use of halothane or cyclopropane may result in increased myocardial sensitization to the catecholamines; dopamine-induced ventricular arrhythmias may be treated with propranolol.
Seizures, hypotension, and bradycardia have been reported if dopamine is used concurrently withphenytoin.
In animals (species not specified), the renal and mesenteric vasodilitation effects of dopamine havebeen antagonized by butyrephenones (e.g., haloperidol), opiates, and phenothiazines.