Clinical therapeutics: The adrenergic system and related drugs

S. Krishnamoorthy*

Group Clinical Pharmacist, Kauvery Hospital, Trichy

*Correspondence: Clinical.cst@kauveryhospital.com

Background

The adrenergic system is an important modulator of synaptic transmission in the central and peripheral nervous system. The endogenous catecholamines epinephrine and norepinephrine activate multiple G protein-coupled receptors (GPCR) to transmit their signal within the neurons.

Alpha Adrenergic Agonists (α Stimulants )

They act on muscles surrounding blood vessels in the dermal skin and cause vasoconstriction.

Drugs

  • Alpha-1 Stimulants : phenylephrine and oxymetazoline
  • Alpha-2 Stimulants : methyldopa and clonidine

Alpha Adrenergic Antagonists ( α Blockers)

Alpha-blockers lower blood pressure by keeping a hormone called norepinephrine from tightening the muscles in the walls of smaller arteries and veins.

Drugs

  • Selective (α Only): Prazosin, Terazosin, Doxazosin, Tamsulosin, Silodosin
  • Non Selective (α & β): Phenoxybenzamine , Phentolamine
  • Alpha-2 blockers : Yohimbine and Idazoxan

Beta Adrenergic Agonists (β Stimulants)

β-adrenergic receptor stimulation (β-ARS) is a physiological mechanism that regulates cardiovascular function under stress conditions or physical exercise

Drugs

  • Beta-1 Stimulants: Adrenaline, Dobutamine and Isoprenaline
  • Beta- Stimulants: Salbutamol, Terbutaline, Salmeterol and Formeterol

Beta Adrenergic Antagonists (β Blockers)

The medicines block the effects of the hormone epinephrine, also known as adrenaline. Beta-blockers cause the heart to beat more slowly and with less force. This lowers blood pressure.

Drugs

  • Only block beta-1 receptors: Acebutolol, Betaxolol, Bisoprolol, Esmolol, and Metoprolol
  • Block both beta-1 and beta-2 receptors: Nadolol, Penbutolol, Pindolol, Propranolol, Sotalol, and Timolol.

Clinical Uses

Alpha Adrenergic Agonists (α Stimulant)

  • Alpha-1 agonists are mainly used to treat hypotension. Other conditions include: Glaucoma (increased intraocular pressure) Septic shock (widespread infection and inflammation that causes organ failure and dangerously low blood pressure)
  • The use of combination of alpha 2 adrenergic agonists with a stimulant is often used in presence of ADHD with comorbid features, specifically oppositional defiant disorder, Giles de Tourette Syndrome (childhood-onset neurodevelopmental disorder that is characterized by several motor and phonic tics) syndrome, and aggressive/impulsive behavior.

Alpha Adrenergic Antagonists (α Blockers)

  • The alpha-1 adrenergic receptor antagonists (also called alpha-blockers) are a family of agents that bind to, inhibit type 1 alpha-adrenergic receptors, and thus inhibit smooth muscle contraction. Their major uses are for hypertension and for symptomatic benign prostatic hypertrophy
  • Alpha-blockers are medications that treat high blood pressure. They can also treat some conditions affecting the circulatory system, prostate, and help with treating certain types of tumors. They work by slowing down specific types of cell activity in your nervous system.

Beta Adrenergic Agonists (β Stimulants)

  • A beta-1 agonist used to treat cardiac decompensation in patients with organic heart disease or from cardiac surgery. A beta blocking agent used to treat hypertension and aid in the management of heart failure
  • Beta-2 agonists commonly manage breathing conditions like asthma and COPD. Providers also use types of beta-agonists during some medical emergencies, and to treat heart conditions, overactive bladder and high potassium levels (hyperkalemia).

Beta-Adrenergic Antagonists (β Blockers)

  • Beta-blockers are indicated and have FDA approval for the treatment of tachycardia, hypertension, myocardial infarction, congestive heart failure, cardiac arrhythmias, coronary artery disease, hyperthyroidism, essential tremor, aortic dissection, portal hypertension, glaucoma, migraine prophylaxis, and other conditions.
  • Beta-1-selective blockers include hypertension, chronic stable angina, heart failure, post-myocardial infarction, and decreased left ventricular function after a recent myocardial infarction.

Monitor these parameters while on these drugs

Alpha Adrenergic Agonists (α Stimulants)

  • Hypotension
  • Bradycardia
  • Xerostomia

Alpha Adrenergic Antagonists (α Blockers)

  • Fast or pounding heartbeat

Beta-Adrenergic Agonists (β Stimulants)

  • Fast heart rate (tachycardia)
  • Irregular heart rate (arrhythmia)
  • High blood pressure (hypertension)

Beta Adrenergic Antagonists (β Blockers)

  • Slow heart rate (bradycardia),
  • Low blood pressure (hypotension)
  • Irregular heart rhythms (arrhythmias).

Conclusion

Communication between nurses, pharmacists, and physicians would  improve the care for the patients needing Adrenergic drugs and prevent side effects and interactions Proper utilization of these agents requires the dedicated attention of health care staff working as a cohesive interprofessional team, who are well acquainted with the patient’s condition and the medications administered.

Reference

  • Cannon WB, Rosenbluth A (31 May 1933). “Studies On Conditions Of Activity In Endocrine Organs XXVI: Sympathin E and Sympathin I”. American Journal of Physiology.
  • Zwieten, Van; A, P. (1986). “Interaction Between α and β-Adrenoceptor-Mediated Cardiovascular Effects”. Journal of Cardiovascular Pharmacology.
  • Beta-2 Agonists https://doi.org/10.1016/B978-0-12-813442-9.00006-7.

 

Mr. Krishnamoorthy
Clinical pharmacist

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