Dopamine

Pharmacological properties

by chemical origin, dopamine is a precursor to the biosynthesis of norepinephrine and has a specific stimulating effect on dopamine receptors, and in high doses it also stimulates α- and β-adrenergic receptors. under the influence of the drug dopamine-darnitsa, OPS and systolic hell increase, heart contractions increase, cardiac output increases. heart rate changes relatively little. myocardial oxygen demand increases, but due to an increase in coronary blood flow, increased oxygen delivery is provided. dopamine-darnitsa reduces the resistance of the renal vessels with an increase in blood flow in them, increases glomerular filtration, sodium excretion. recorded pharmacological effects depend on the concentration of the active substance in the blood. at low doses (0.5–2 μg / kg / min), it mainly affects dopamine receptors. expands mesenteric, brain, coronary vessels, reduces renal vascular resistance, increases glomerular filtration, increases diuresis and excretion of sodium from the body.

In the range of medium doses (2–10 μg / kg / min), it stimulates β₁-adrenoreceptors, which causes a positive inotropic effect, increases cardiac output.

At doses of 10 μg / kg / min and higher, it affects α more₁-adrenoreceptors, which increases the OPSS, narrows the renal vessels, increases blood pressure, reduces diuresis.

After cessation of administration, the effect lasts no more than 5-10 minutes.

Pharmacokinetics Since dopamine is a natural intermediate of the synthesis of norepinephrine, it is impossible to track its pharmacokinetics in the body in most cases.

After the introduction of T_½ up to 5 minutes (average 2 minutes). It is metabolized in almost all tissues. 75% of the administered dose is excreted from the body during the first day by the kidneys in the form of inactive metabolites. Up to 25% of injected dopamine by the reuptake mechanism in neurovesicles is used to synthesize norepinephrine. The onset of action is within 5 minutes after the start of administration, the end is 5–10 minutes after the end of the infusion.

Indications

Shock or conditions threatening shock:

• heart failure caused by acute myocardial infarction (cardiogenic shock);
• severe infections (toxic shock);
• state of shock after surgery;
• marked reduction in blood pressure (severe arterial hypotension) of any genesis;
• hypersensitivity reactions (anaphylactic shock).

Application

The doctor prescribes the dose of the drug individually, taking into account the severity of the shock, the patients reaction to dopamine treatment, and side effects. to obtain the desired effect of dopamine on hemodynamics, the dose of each patient should be carefully selected by titration.

Before starting the course of treatment, it is necessary to restore the BCC. Simultaneously with the use of dopamine, electrolyte balance should be monitored.

If the doctor has not prescribed another, the following doses are recommended: for adult patients, who are likely to respond to moderate maintenance of the functioning of the heart and blood circulation, dopamine can be infused at an initial dose of 2-5 mg / kg body weight per minute.

In this case, for seriously ill patients, the initial dose should be 5 mg / kg body weight, and if necessary, it can be gradually increased (for example, every 15-30 minutes) to 5-10 mg / kg body weight per minute to a maximum of 20-50 mg / kg body weight per minute.

In most patients, it is possible to achieve a satisfactory condition when using doses of dopamine below 20 mg / kg body weight per minute. The use of the drug at a dose of 20 mg / kg body weight per minute may be accompanied by a decrease in renal blood flow.

If heart failure worsens, dopamine should be used as an infusion at a dose of not more than 50 mg / kg body weight per minute.

If there is a need for a dose higher than 50 mg / kg body weight per minute, diuresis should be monitored.

It is necessary to give preference to increasing the rate of administration of the drug with low concentrations before the introduction of a more concentrated solution.

The tables below show the rate of administration of the drug for various dosages and various initial concentrations.

If 1 ampoule of Dopamine-Darnitsa, concentrate for the preparation of a solution for infusion, 40 mg / ml, is diluted in 50 ml of a solution for infusion, 1 ml of this solution contains 4000 μg of dopamine hydrochloride.

If 1 ampoule of Dopamine-Darnitsa, a concentrate for the preparation of a solution for infusion, 40 mg / ml, is diluted in 500 ml of a solution for infusion, 1 ml of this solution contains 400 μg of dopamine hydrochloride.

The duration of treatment depends on the clinical condition of the patient and is determined by the doctor.

Before starting treatment with dopamine in patients with hypovolemia, BCC should be restored. Given that dopamine improves atrial ventricular conduction, patients with fibrillation and a quick response should be given cardiac glycosides before dopamine is prescribed.

In the treatment of patients in an unconscious state, due to the risk of aspiration, airway patency should be monitored. Patients with increased pre- and afterload in order to reduce the load on the heart should additionally use nitroglycerin.

Before administration, the drug must be diluted. The dilution volume is 1 ampoule per 250 ml or 500 ml of the solvent recommended for use (0.9% sodium chloride solution or 5% glucose solution).

A solution for infusion must be prepared immediately before use, using only transparent solutions that do not change color after the addition of Dopamine-Darnitsa. Infusion, if possible, should be carried out using a central venous catheter.

The finished solution should be used within 12 hours.

Contraindications

Hypersensitivity to dopamine or other components of the drug. pheochromocytoma, thyrotoxicosis. tachyarrhythmia, ventricular fibrillation, as well as conditions accompanied by mechanical resistance to filling the ventricles. hypovolemia (before the start of treatment, it is necessary to restore the deficiency of bcc). glaucoma. prostatic hyperplasia with urinary retention. Anesthesia with cyclopropane and halogenated hydrocarbons must be avoided.

Side effects

The development of adverse reactions with dopamine is associated with the pharmacological effect of the drug.

On the part of the central and peripheral nervous system: headache, anxiety, anxiety, a sense of fear, tremor, piloerektion.

From the sensory organs: mydriasis.

From the digestive tract: nausea, vomiting, bleeding from the digestive tract.

From the cardiovascular system: palpitations, cardiac arrhythmias, including tachycardia (ventricular, supraventricular and sinus), bradycardia, arrhythmia (extrasystole, ventricular extrasystole, ventricular arrhythmia), ectopic heart rhythm, aberrant conduction, ventricular conduction AV block, expansion of the QRS complex; pain behind the sternum, anginal pain, myocardial ischemia, angina pectoris, increased pressure in the ventricles, increased blood pressure, arterial hypotension, spasm of peripheral arteries, vasoconstriction, bleeding.

From the urinary system: polyuria.

On the part of the respiratory system: shortness of breath. In patients with respiratory failure, there is an increase in hypoxemia characteristic of increased blood circulation