📖 Pharmacology
Beta - Adrenergic Blocking Agents
Pharmacology Beta - Adrenergic Blocking Agents
Mechanisms of Action
- Initial decrease in cardiac output, followed by reduction in peripheral vascular resistance.
- Other actions include decrease plasma renin activity, resetting of baroreceptors, release of vasodilator prostaglandins, and blockade of prejunctional beta-receptors.
Advantages
- Documented reduction in cardiovascular morbidity and mortality.
- Cardioprotection: primary and secondary prevention against coronary artery events (i.e. ischemia, infarction, arrhythmias, death).
- Relatively not expensive.
Considerations
- Beta blockers are used with caution in patients with bronchospasm.
- Contraindicated in more than grade I AV, heart block.
- Do not discontinue abruptly.
Side Effects
- Bronchospasm and obstructive airway disease.
- Bradycardia
- Metabolic effects (raise triglyerides levels and decrease HDL cholesterol; may worsen insulin sensitivity and cause glucose intolerance). Increased incidence of diabetes mellitus.
- Coldness of extremities.
- Fatigue.
- Mask symptoms of hypoglycemia.
- Impotence.
Indications
- First line treatment for hypertension as an alternative to diuretics.
- Hypertension associated with coronary artery disease.
- Hyperkinetic circulation and high cardiac output hypertension (e.g., young hypertensives).
- Hypertension associated with supraventricular tachycardia, migraine, essential tremors, or hypertrophic cardiomyopathy.
Beta adrenergic blocker Drugs
Atenolol 25-100
Metoprolol 50-200
Bisoprolol 2.5-10
Topical Anesthetics
PharmacologyTopical Anesthetics
Benzocaine
Benzocaine is a derivative of procaine, an ester type local anesthetic, and is poorly soluble in water and is
available only as a topical anesthetic.
- Localized allergic reactions are sometimes encountered
- Overdosing is unlikely as benzocaine is poorly absorbed into the blood, which decreases the likelihood of systemic toxicity.
- The onset of surface anesthesia is rapid requiring less than one minute.
Tetracaine
- Tetracaine is an ester type local anesthetic
- Topically applied tetracaine as opposed to benzocaine has a prolonged duration of action.
Cocaine
- Cocaine is a ester type anesthetic that is used exclusively as a topical agent.
- Cocaine is unique among topical and injectable anesthetics in that it has vasoconstrictive as well as anesthetic properties. It is used sparingly because of its abuse potential but is still used when hemostasis of mucous membranes is essential.
- Cocaine is generally available in concentrations of 2-10 % solution.
Lidocaine
- Lidocaine is an amide local anesthetic that is available in injectable and topical formulations.
- It is available in gel, viscous solution, ointment and aerosol preparations in concentrations ranging from 2-10 %.
- The onset of anesthesia is slower relative to benzocaine but, the duration is about the same.
- Absorption into the bloodstream is greater than benzocaine providing a greater risk of systemic toxicity.
Drugs Used in Diabetes -Megltinides
PharmacologyMegltinides
nateglinide
repaglinide
Mechanism
binds to K+ channels on β-cells → postprandial insulin release
Clinical use
type 2 diabetes mellitus
may be used as monotherapy, or in combination with metformin
DOPAMINE
PharmacologyDOPAMINE
It is an immediate metabolic precursor of noradrenaline. It activates D1 receptors in several vascular beds, which causes vasodilatation. It acts on dopaminergic and other adrenergic receptors (α & β1).
Adverse effects of dopamine include nausea, vomiting, ectopic beats, anginal pain, tachycardia, palpitation and widened QRS.
Contraindications are atrial or ventricular tachyarrhythmias, hyperthyroidism and pheochromocytoma.