The sympathomimetics are drugs which bind to adrenergic receptors to stimulate or turn on the receptor to which they have bonded. This translates into the turning on of some cellular process that is mediated by the adrenergic receptor. These drugs are able to turn on an alpha, beta-1, and/or a beta-2 receptor.
Receptor Types : alpha, beta-1, beta-2
alpha Adrenergic Receptors - are responsible for peripheral vasoconstriction
beta-1 Adrenergic Receptors - are responsible for H.R., force of contraction, S.V.
beta-2 Adrenergic Receptors - are responsible for vasodilatation and bronchodilatation
The Mechanism Of Action For The Sympathomimetics On The beta-2 Adrenergic Receptor
1. Drug-receptor complex activates the Gs protein which in turn cleaves an ATP to make cAMP - a second messenger.
2. cAMP blocks the activation of an enzyme called Myosin Light Chain Kinase (MLCK) which would normally phosphorylate myosin (adding a PO4- group) thus activating the myosin head to interact with actin. Since cAMP blocks the activation of MLCK, then myosin light chain (MLC20) cannot be phosphorylated (activated) and thus smooth muscle relaxes because no interaction can occur between actin and myosin. You, therefore get permissive bronchodilation.
Epinephrine (Adrenaline) - alpha, beta-1, beta-2
Norepinephrine (Levophed) - alpha, beta-1, beta-2
Isoproterenol (Isuprel) - beta-1, beta-2
Metaproterenol (Metaprel, Alupent) - beta-2
Terbutaline Sulfate (Brethine) - beta-2
Albuterol Sulfate (Ventolin) - beta-2
Isoetharine Hcl (Bronkosol) - beta-2
Pirbuterol (Maxair) - beta-2
Bitolterol Mesylate (Tornalate) - beta-2
Medical Uses Of The Sympathomimetics
1. Bronchodilation - Stimulation of the beta-2 adrenergic receptor
2. Increases In Blood Pressure - Stimulation of the alpha adrenergic receptor
3. Increases In Cardiac Output - Stimulation of the beta-1 adrenergic receptor
Special Medical Uses Of The Sympathomimetics
1. Terbutaline Sulfate (Brethine), Fenoterol, and Ritodrine HCl (Yutopar) are used to inhibit premature labor. They are beta-2 selective sympathomimetics with the effect of relaxing the uterine muscle.
Adverse Side Effects Of The Sympathomimetics :
Nausea, vomiting, headaches, dizziness, irritability, nervousness, seizures, tremors, anxiety, insomnia, hypertension, palpitations, tachycardia, arrhythmias, stroke, cardiac arrest, angina, bradycardia.
Clinical Considerations In Physical Therapy Practice For The Sympathomimetics
1. Clearing Secretions From The Patient’s Lung Fields : Help your patient to clear secretions from their lungs. There are a number of things we can do to assist the patient in this way :
b. Chest Physical Therapy (CPT) has been part of our licensure since the beginning of our profession. Some of the tools that we can use to help the patient get rid of secretions from their lungs are : Postural Drainage, Percussion, Diaphragmatic Breathing, Deep Breathing and Coughing Exercises.
3. Know Your Patient’s Medicines and Medical History : Know which of your patients has chronic obstructive pulmonary disease (COPD) and what medications they are currently using.
4. Medication Side Effects : Know the side effects of those medications.
The Methylxanthines are a group of medications which are largely used to bronchodilate an individual. Members : 1. Theophylline (Theo-Dur, Uniphyl)
Mechanisms of Action For The Methylxanthines
General Actions Of The Methylxanthines :
Medical Uses Of The Methylxanthines :
Special Uses Of The Methylxanthines
1. The Treatment Of Neonatal Apnea : The methylxanthines are used to stimulate the respiratory centers in neonates. Caffeine and theophylline are often the drugs of choice.
Adverse Side Effects : Seizures (too much Methylxanthine on board), nervousness, insomnia, headaches, tachycardia, tachdysrhythmias, nausea, anorexia, vomiting, diarrhea.
Clinical Considerations In Physical Therapy Practice For The Methylxanthines 1. Seizures Precautions : Watch the patient for the onset of CNS seizures. These drugs cause patients to have seizures when there is too much of the medication in the blood stream. These drugs have small therapeutic windows. A consciencous physician will do blood titers to make sure that the patient is not getting too much of the drug. 2. Side Effects : Understand the side effects of these drugs. Patients will feel quite “jumpy” and nervous on these medications and may need to be reassured. Also, the patient is frequently irritable and demonstrates some rude behaviors when on these medications. It helps to understand the side effects so that the clinician does not take the patient’s rudeness to heart.
Mechanisms of Action :
1. N-Acetylcysteine ( Mucomyst, Airbron) breaks the disulfide bonds in mucin thus making the mucin thinner and more easily transported out of the lungs by the MCE.
2. Recombinant Human Deoxyribonuclease I (rhDNase, Dornase) is an enzyme that cleaves DNA left behind by neutrophils in the lungs. When a neutrophil dies, its DNA leaks out of the cell and when it comes into contact with mucin, it makes the mucin very thick and tenacious. This is a particular problem with patients with Cystic Fibrosis. Consequently, when Dornase is inhaled, it cuts apart the neutrophil DNA and makes the mucin thinner and more easily removed by the MCE.
Medical Uses Of The Mucolytics :
1. Mucomyst is used to reduce the secretions in patients with COPD (asthma, bronchitis, bronchiectasis and emphysema).
2. Dornase is used to thin the secretions in patients with cystic fibrosis. This drug is so effective, that the pulmonary function test values in these patients rises dramatically, the incidence of lung infections is reduced dramatically and life is prolonged.
Special Uses Of N-Acetylcysteine (Mucomyst)
1. This medication is given orally to children who have overdosed on Tylenol. Mucomyst binds with Tylenol and prevents it from corrosively destroying the kidney.
Adverse Side Effects Of The Mucolytics :
1. Always give these medications by a metered inhaler or by SVN 1 hour prior to other chest PT treatments.
Mechanisms Of Action :
1. Stimulates the mucin secreting cells to hyperactively produce mucin. This mucin is thinner with a higher water content and is, therefore, more easily removed by the MCE.
2. The increased volume of thiiner mucin helps to stimulate coughing.
Mechanisms Of Action :
Medical Uses Of The Inhaled Corticosteroids
The Safety And Advantages Of Inhaled Corticosteroids
Adverse Side Effects : Irritation of the mucosal membranes, dry mouth, hoarseness, sore throat, candidal infections of the mouth.
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