Adrenergic System Drugs

Adrenergic System Drugs: Beta-3 Agonist - Mirabegron

Mirabegron is a beta-3 agonist.

These receptors are primarily found in adipose (fat) tissue and the bladder.

Mirabegron targets the beta-3 receptors that are found in the urothelium (epithelial tissue that lines the urinary tract) and detrusor muscles (smooth muscle in the wall of the urinary bladder).

By stimulating the beta-3 receptor, it relaxes the detrusor muscle during the storage phase of the bladder fill cycle, which increases the bladder capacity.

It is indicated for relief of overactive bladder (OAB), including urge urinary incontinence, urgency, and frequency.

Mirabegron Side effects

Increased blood pressure

Tachycardia

Mirabegron Adverse reactions

Angioedema

Urinary tract infection

Mirabegron interactions

It may increase levels and risk of toxicity with digoxin.

Use cautiously in renal and hepatic impairment.

It should not be used with certain chemotherapy agents.

Mirabegron considerations

Sustained-release tablets cannot be chewed or crushed.

Monitor blood pressure.

Monitor for signs of angioedema (swelling of face, lips, tongue, and/or larynx) and seek immediate medical attention.

Adrenergic System Drugs: Alpha-1 Agonist and Vasopressor - Phenylephrine

Phenylephrine works by narrowing the blood vessels in the nose area, reducing swelling and congestion.

It constricts blood vessels by stimulating alpha-adrenergic receptors.

Additional Indications for Use:

Phenylephrine is also used as a vasopressor in the management of hypotension associated with shock that may persist after adequate fluid replacement.

Phenylephrine is both an alpha-1 agonist and a vasopressive drug (pressor). This medication is used for temporary relief of congestion in the nose caused by various conditions including the common cold, sinusitis, hay fever, and allergies.

The intranasal application of certain adrenergic medications can cause the constriction of dilated arterioles and a reduction in nasal blood flow, which thus decreases congestion. These adrenergic drugs work by stimulating alpha-1-adrenergic receptors and have little or no effect on beta-adrenergic receptors.

Phenylephrine Side effects

Tachycardia

Headache

Dizziness

Burning

Stinging

Dryness of nares

Runny nose

Sneezing

Phenylephrine Adverse effects

Arrhythmias

Trouble breathing

Rash

Swelling of tongue/face/throat

Phenylephrine Medication interactions

An adrenergic crisis caused by combining phenylephrine and monoamine oxidase inhibitors (MAOIs) can occur within minutes.

Taking MAO inhibitors may cause a serious (possibly fatal) drug interaction, leading to a hypertensive crisis. Concurrent ingestion can result in a life-threatening hypertensive crisis. Signs and symptoms of hypertensive crisis include chest pain, tachycardia or bradycardia, severe headache, neck stiffness or soreness, nausea and vomiting, sweating, photosensitivity, and enlarged pupils. Seek immediate emergent care.

Phenylephrine Considerations

Avoid spraying the medication into your eyes or onto the middle of the inside of your nose.

Do not use this medication for more than 3 days, or it may cause a condition called rebound congestion. Symptoms of rebound congestion include long-term redness and swelling inside the nose and an increased runny nose.

Adrenergic System Drugs: Peripherally Acting Anti-Adrenergic/Alpha-1-Adrenergic Blocker - Doxazosin

Dilates both arteries and veins by blocking postsynaptic alpha-1-adrenergic receptors, making it easier for blood to flow.

Lowers blood pressure.

Increases urine flow and decreases symptoms of BPH by relaxing the muscles in the prostate and bladder neck.

Additional Indication for Use

Symptomatic benign prostatic hyperplasia (BPH)

Doxazosin is a peripherally acting anti-adrenergic/alpha-1-adrenergic blocker used to treat hypertension.

Doxazosin Side effects

First-dose orthostatic hypotension

First-dose syncope

Tachycardia/palpitations

Dizziness

Headache

Dyspnea

Doxazosin Adverse reactions

Hypersensitivity

Chest pain

Doxazosin Interactions

Use cautiously for those with hepatic impairment.

Nonsteroidal anti-inflammatory (NSAIDs), sympathomimetics, or estrogens may decrease the effects of antihypertensive therapy.

Avoid concurrent use of alcohol or over-the-counter (OTC) medications and herbal products, especially cold preparations.

Doxazosin Considerations

The first-dose phenomenon, which is a severe and sudden drop in blood pressure after the administration of the first dose of an alpha-adrenergic blocker, can cause clients to fall or pass out.

Monitor blood pressure and pulse 2-6 hours after the first dose, with each increase in dose, and periodically during therapy (weekly monitoring).