sympathomimetic

sympathomimetic /sym·pa·tho·mi·met·ic/ (-mi-met´ik)

1. mimicking the effects of impulses conveyed by adrenergic postganglionic fibers of the sympathetic nervous system.

2. an agent that produces such an effect.

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sym·pa·tho·mi·met·ic (smp-th-m-mtk, -m-)

adj.

Producing physiological effects resembling those caused by the action of the sympathetic nervous system.

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sympa·tho·mi·metic n.

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Sympathomimetic

Denoting a drug that mimics the effects of stimulation of organs and structures by the sympathetic nervous system. The sympathetic nervous system pertains to the part of the nervous system originating in the thoracic and lumbar regions of the spinal cord. In general, it inhibits or opposes the physiological effects of another aspect of the nervous system, as in tending to reduce digestive secretions, speed up the heart, and contract the blood vessels.

Mentioned in: Tilt Table Test

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sympathomimetic

[sim′pəthō′mimet′ik]

Etymology: Gk, sympathein + mimesis, imitation

a pharmacologic agent that mimics the effects of stimulation of organs and structures by the sympathetic nervous system. It functions by occupying adrenergic receptor sites and acting as an agonist or by increasing the release of the neurotransmitter norepinephrine at postganglionic nerve endings. Various sympathomimetic agents are used as decongestants of nasal and ocular mucosa, such as bronchodilators in the treatment of asthma and vasopressors and cardiac stimulants in the treatment of acute hypotension and shock; they are also used for maintaining normal blood pressure during operations using spinal anesthesia. Drugs in this group include cyclopentamine, DOBUTamine, DOPamine, epHEDrine, isoproterenol, metaproterenol, metaraminol, mephentermine, methoxamine, methoxyphenamine, naphazoline, norepinephrine, phenylephrine, propylhexedrine, protokylol, pseudoephedrine, terbutaline sulfate, tetrahydrozoline, tuaminoheptane, xylometazoline, and epINEPHrine, a synthetic isomer of the hormone secreted by the adrenal medulla. Adverse effects of sympathomimetic drugs may be nervousness, severe headache, anxiety, vertigo, nausea, vomiting, dilated pupils, glycosuria, and dysuria. Also called adrenergic drug.

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sympathomimetic (sim´pthōmimet´ik),

adj resembling the effect produced by stimulation of the sympathetic nervous system. See also adrenergic.

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sympathomimetic

adrenergic: producing effects resembling those of impulses transmitted by the postganglionic fibers of the sympathetic nervous system. Also, an agent that produces such an effect.

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dobutamine hydrochloride

Pharmacologic class: Sympathomimetic, adrenergic

Therapeutic class: Inotropic

Pregnancy risk category B

Action

Stimulates beta₁-adrenergic receptors of heart, causing a positive inotropic effect that increases myocardial contractility and stroke volume. Also reduces peripheral vascular resistance, decreases ventricular filling pressure, and promotes atrioventricular conduction.

Availability

Injection: 12.5 mg/ml in 20-ml vials

⊘Indications and dosages

➣ Short-term treatment of cardiac decompensation caused by depressed contractility (such as during refractory heart failure); adjunct in cardiac surgery

Adults: 2.5 to 10 mcg/kg/minute I.V. as a continuous infusion, adjusted to hemodynamic response

Dosage adjustment

• Elderly patients

Off-label uses

• Adjunct in myocardial infarction (MI) and septic shock
• Diagnosis of coronary artery disease (echocardiography stress test, ventriculography, computed tomography)

Contraindications

• Hypersensitivity to drug
• Idiopathic hypertrophic subaortic stenosis

Precautions

Use cautiously in:
• hypertension, MI, atrial fibrillation, hypovolemia
• pregnant or breastfeeding patients
• children.

Administration

• Use infusion pump or microdrip I.V. infusion set.
• Dilute with dextrose 5% in water or normal saline solution to at least 50 ml of solution. Know that drug is incompatible with alkaline solutions, such as sodium bicarbonate injection.

Route	Onset	Peak	Duration
I.V.	1-2 min	10 min	Brief

Adverse reactions

CNS: headache

CV: hypertension, hypotension, tachycardia, premature ventricular contractions, angina, palpitations, nonspecific chest pain, phlebitis

GI: nausea, vomiting

Metabolic: hypokalemia

Respiratory: dyspnea, asthma attacks

Skin: extravasation with tissue necrosis

Other: hypersensitivity reactions including anaphylaxis

Interactions

Drug-drug. Beta-adrenergic blockers: increased alpha-adrenergic effects

Bretylium: potentiation of vasopressor activity

Cyclopropane, halothane: serious arrhythmias

Guanethidine: decreased hypotensive effects

Thyroid hormone: increased cardiovascular effects

Tricyclic antidepressants: potentiation of cardiovascular and vasopressor effects

Drug-herbs. Rue: increased inotropic potential

Patient monitoring

• As needed, correct hypovolemia before starting therapy by giving volume expanders, as prescribed.
• Monitor ECG and blood pressure continuously during administration.
• Monitor fluid intake and output.
☞ Assess electrolyte levels. Stay especially alert for hypokalemia.

Patient teaching

• Instruct patient to report anginal pain, headache, leg cramps, and shortness of breath.
• Explain need for close observation and monitoring.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and herbs mentioned above.