Adrenergic Blockers (Antagonists)

Alpha Adrenergic Antagonists (Alpha Blockers)

• Mechanism of Action
  • Alpha blockers function by blocking the $alpha_1$ receptor sites.
  • The physiological results of this blockade include:
    • Vasodilation of the blood vessels.
    • A decrease in blood pressure.
    • Pupil constriction.
    • Reduced contraction of the smooth muscle located in the prostate and the bladder neck.
• Clinical Indications and Uses
  • These medications are utilized for patients who are hypertensive.
  • They are prescribed for Benign Prostatic Hypertrophy (BPH).
  • They are used in the treatment of Raynaud’s disease.
• Pharmacological Identification
  • All drugs within this specific class are identified by the suffix ‘sin’.
  • These medications work primarily on the blood vessels.

Beta Adrenergic Antagonists (Beta Blockers) Mechanisms

• $Beta_1$ Blocker Action
  • These agents block beta-adrenergic receptor sites.
  • They cause a decrease in the movement of epinephrine.
  • They suppress the renin-angiotensin-aldosterone system.
  • The primary cardiac effects include a decrease in heart rate and a reduction in the force of myocardial contractions.
• $Beta_2$ Blocker Action
  • Blockade of these receptors results in bronchoconstriction.
  • It causes the uterus to contract.
  • It inhibits the process of glycogenolysis.
  • The inhibition of glycogenolysis leads to a state of hypoglycemia.

Classification and Selectivity of Beta Blockers

• Clinical Uses of Beta Blockers (e.g., Atenolol)
  • Hypertension (hypertensive patients).
  • Angina.
  • Heart failure.
  • Dysrhythmias.
• Pharmacological Identification
  • Drugs in this class are identified by the suffix ‘olol’.
  • These medications target both the heart and the blood vessels.
• Selectivity Rules for ‘olol’ Drugs
  • Selective: If the drug name starts with a letter between A and M, it is more selective to $beta_1$ receptors.
  • Non-selective: If the drug name starts with a letter between N and Z, it is non-selective, meaning it blocks both $beta_1$ and $beta_2$ receptor sites.

Side Effects and Adverse Reactions of Beta Blockers

• Common Side Effects
  • The side effects of beta blockers are generally the opposite of those produced by adrenergic drugs.
  • Neurological/Psychological effects include drowsiness, dizziness, headaches, and depression.
  • Reproductive effects include decreased libido.
• Adverse Reactions
  • Hypotension.
  • Bradycardia.
  • Masking of hypoglycemia (the physiological signs of low blood sugar are hidden).

Contraindications and Drug Interactions

• Contraindications
  • Heart block.
  • Bradycardia.
  • Cardiogenic shock.
  • Pregnancy.
• Precautions/Cautionary Use
  • Renal dysfunction.
  • Diabetes.
  • Acute bronchospasms.
• Drug Interactions
  • NSAIDS: Result in a decreased effect of the beta blocker.
  • Antihypertensives and Antidysrhythmics: Result in an increased effect when taken concurrently with beta blockers.
  • Insulin and Sulfonylureas: Lead to an increased risk of hypoglycemia and the masking of hypoglycemic symptoms.

Nursing Process: Assessment and Interventions

• Nursing Assessment
  • Establish baseline vital signs.
  • Obtain an Electrocardiogram (EKG).
  • Review all current medications the patient is taking.
  • Conduct a thorough health history.
• Nursing Interventions
  • Monitor vital signs continuously.
  • Report marked changes in blood pressure.
  • Report a pulse that drops below $60$ beats per minute.
  • Report bothersome side effects that do not show improvement, specifically dizziness, lightheadedness, a stuffy nose, or depression.
  • Safety precautions must be provided due to the risk of orthostatic hypotension.

Patient Teaching and Evaluation

• Patient Education
  • The medication must be taken at the same time every single day.
  • The patient should be informed that the full therapeutic effect may take several weeks to achieve.
  • The patient is required to monitor their own blood pressure and pulse, maintaining a written record.
  • Patients must be instructed to get up slowly from a sitting or lying position to help prevent orthostatic hypotension.
  • The patient must report any adverse reactions immediately.
  • Instruct the patient not to drive until their individual response to the drug has been determined.
• Evaluation of Treatment
  • Success is determined by a decrease in blood pressure.
  • Success is determined by a decrease in pulse.
  • Confirmation that side effects are being managed effectively.

Questions & Discussion

• Question: The nurse is caring for a client who is taking Atenolol. What is considered an adverse reaction?
  • A. Hypertension
  • B. Erectile dysfunction
  • C. Renal failure
  • D. Depression
• Answer: C: Renal failure.