Beta-Agonist

1. Abstract

2. Introduction

3. Example of beta agonist

4. Mechanism of action

5. Examples of beta agonist drugs

6. Dose

7. Side effects

8. Benefits

9. Risks

10. Pharmacokinetic properties

11. Drug - Drug interaction

12. Drug - Food interaction

13. Monograph

1-Abstract:

 Beta-adrenergic agonists, or β agonists, are a class of medications primarily used in the management of respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD). They work by binding to beta-adrenergic receptors in the body, particularly β2 receptors in the smooth muscle of the airways in the lungs. Upon activation, β agonists induce bronchodilation, decrease inflammation, and may enhance mucociliary clearance, and thereby improving airflow.

3-Examples of beta agonists:

There are beta-1, beta-2 and beta-3 receptors.

Beta-1 agonists: bind to receptors in your heart. This causes:

• ·Heart to beat faster

• ·Pump blood with more force.

•  Used to treat certain heart conditions.                                     

  Beta-2 agonists: most commonly, bind to receptors in your lungs.

• Relaxes the muscles in your airways

• Commonly used to treat COPD and asthma.

Beta-3 agonists: fairly new class of medications.

• Relax your bladder muscles to reduce your urge to pee.

• Treat overactive bladder.

 4-Mechanism of action :

• Beta-agonists use alpha- and beta-receptors. Beta-agonists work on parts of your sympathetic nervous system which diverting your body’s resources to the most critical organ functions like those in your muscles, lungs and heart including:

     1 - Relaxing your muscles in your lungs to allow you to breathe easier.

     2 - Increasing your heart rate to pump oxygen-rich blood to your muscles.

     3 - Relaxing your bladder to hold more pee (urine) .

• In contrast, beta-blockers block the receptors so agonists can’t latch on. This keeps the receptors from getting activated.

Selective beta-agonists only target beta-receptors in certain parts of your body. Nonselective beta-agonists target all of your beta-receptors.

• Overall, β agonists help alleviate symptoms of airway constriction, improve airflow, and facilitate breathing in conditions characterized by bronchoconstriction, such as asthma and COPD.

5-Some examples of beta-agonist drugs include:

• Short-Acting B-Agonists (4-6 h)

• Albuterol

• Levalbuterol

• Pirbuterol

• Terbutaline

• Metaproterenol

• Long-Acting B-Agonists (12 h)

• Arformoterol

• Bambuterol

• Clenbuterol

• Formoterol

• Salmeterol

• Protokylol

• Approved Ultralong-Acting B-Agonists (24 h)

• Indacaterol

Sadaterol

• Vilanterol (in association with other drugs only.

6-Dose.

1. Short-acting beta2-agonists (SABAs):

   - Albuterol (salbutamol): The usual dose for inhalation is 1-2 inhalations (90-180 mcg) every 4-6 hours as needed for quick relief of acute symptoms.

2. Long-acting beta2-agonists (LABAs):

   - Formoterol (e.g., Foradil, Perforomist): The usual dose varies depending on the specific formulation and indication, but typical dosing regimens may include one inhalation (e.g., 12 mcg) twice daily.

7 - 8 - 9

10- pharmacokinetic properties of beta agonists:

1.    Absorption: Beta agonists can be administered via inhalation, oral ingestion, or intravenous injection. The absorption rate and bioavailability can vary depending on the route of administration.

2.    Distribution: Beta agonists distribute throughout the body via the bloodstream and can reach target tissues.

3.    Metabolism: occurs in the liver via enzymes like cytochrome P450. Some beta agonists undergo significant first-pass metabolism when taken orally, reducing their bioavailability.

4.    Excretion:excreted through the kidneys, either unchanged or as metabolites. The elimination half-life varies between different beta agonists.

11- Drug -Drug interaction

Some important drug interactions involving beta agonists include:

·   Beta Blockers:Beta agonists stimulate beta-adrenergic receptors, leading to bronchodilation and increased heart rate.

·   Diuretics: cause electrolyte imbalances such as hypokalemia (low potassium levels),

·   Corticosteroids:  used in combination with inhaled corticosteroids for asthma management.

·   Monoamine Oxidase Inhibitors (MAOIs):  prolonging their action and increasing the risk of cardiovascular side effects.

12- Drug - Food interaction

There are some general considerations and potential interactions to be aware of:

·   Grapefruit Juice:grapefruit juice can inhibit certain enzymes in the intestine (specifically CYP3A4).

·   High-Protein Meals:increase the metabolism of certain beta agonists.

·   Caffeine: has stimulant effects similar to beta agonists.

·   Tyramine-Containing Foods: cause a hypertensive crisis when combined with certain medications .