NEET MDS Lessons
Pharmacology
Class I Sodium Channel Blockers
• Block movement of sodium into cells of the cardiac conducting system
• Results in a stabilizing effect and decreased formation and conduction of electrical impulses
• Have a local anesthetic effect
• Are declining in use due to proarrhythmic effects and increased mortality rates
• Na channel blockers - Class 1 drugs are divided into 3 subgroups
• 1A. 1B, 1C based on subtle differences in their mechanism of action.
• Blockade of these channels will prevent depolarization.
• Spread of action potential across myocardium will slow and areas of pacemaker activity is suppressed.
Class IA Sodium Channel Blockers
• Treatment of: symptomatic premature ventricular contractions, supraventricular tachycardia, and ventricular tachycardia, prevention of ventricular fibrillation
– Quinidine (Cardioquin, Quinaglute)
– Procainamide (Pronestyl, Procanbid)
– Disopyramide (Norpace)
• Quinidine – prototype
• Low therapeutic index
• High incidence of adverse effects
Class IB Sodium Channel Blockers
• Treatment of: symptomatic premature ventricular contractions and ventricular tachycardia, prevention of ventricular fibrillation
– Lidocaine (Xylocaine)
– Mexiletine (Mexitil)
– Tocainide (Tonocard)
– Phenytoin (Dilantin)
Side Effects: Lidocaine
• Drowsiness • Paresthesias • Muscle twitching • Convulsions • Changes in mental status (disorientation, confusion) • Hypersensitivity reactions (edema, uticaria, anaphylaxis)
Side Effects: Phenytoin (Dilantin)
• Gingival hyperplasia
• Nystagmus
• Ataxia, slurring of speech
• Tremors
• Drowsiness
• Confusion
• Lidocaine – prototype
• Must be given by injection
• Used as a local anesthetic
• Drug of choice for treating serious ventricular arrhythmias associated with acute myocardial infarction, cardiac surgery, cardiac catheterization and electrical conversion
Class IC Sodium Channel Blockers
• Treatment of: life-threatening ventricular tachycardia or fibrillation and supraventricular tachycardia unresponsive to other drugs
– Flecainide
– Propafenone
Adverse Effects
• CNS - dizziness, drowsiness, fatigue, twitching, mouth numbness, slurred speech vision changes, and tremors that can progress to convulsions.
• GI - changes in taste, nausea, and vomiting. CV - arrhythmias including heart blocks, hypotension, vasodilation, and potential for cardiac arrest.
• Other Rash, hypersensitivity reactions loss of hair and potential bone marrow depression.
Drug-Drug Interactions
• Increased risk for arrhythmias if combined with other drugs that are know to cause arrhythmias- digoxin and beta blockers
• Increased risk of bleeding if combined with oral anticoagulants.
Drug Food Interactions
• Quinidine needs an acidic urine for excretion. Increased levels lead to toxicity
• Avoid foods that alkalinize the urine- citrus juices, vegetables, antacid, milk products
Classification
I) Esters
1. Formed from an aromatic acid and an amino alcohol.
2. Examples of ester type local anesthetics:
Procaine
Chloroprocaine
Tetracaine
Cocaine
Benzocaine- topical applications only
2) Amides
1. Formed from an aromatic amine and an amino acid.
2. Examples of amide type local anesthetics:
Articaine
Mepivacaine
Bupivacaine
Prilocaine
Etidocaine
Ropivacaine
Lidocaine
Fluconazole: an antifungal used orally, intravenously or vaginally to treat yeast and fungal infections. Side-effects of systemic administration include hepatotoxicity (liver damage).
- For vaginal candidiasis (vaginal thrush), a once-only oral dose is often sufficient.
PLASMA FRACTIONS:
a) Fresh frozen plasma.
b) Platelets.
c) Plasma concentrates.
d) Non-plasma recombinant factor concentrates.
Azithromycin
Azithromycin is the first macrolide antibiotic belonging to the azalide group. Azithromycin is derived from erythromycin by adding a nitrogen atom into the lactone ring of erythromycin A, thus making lactone ring 15-membered.
Azithromycin has similar antimicrobial spectrum as erythromycin, but is more effective against certain gram-negative bacteria, particularly Hemophilus influenzae.
azithromycin is acid-stable and can therefore be taken orally without being protected from gastric acids.
Main elimination route is through excretion in to the biliary fluid, and some can also be eliminated through urinary excretion
Doxycycline
Commonly prescribed for infections and to treat acne. treat urinary tract infections, gum disease, and other bacterial infections such as gonorrhea and chlamydia., as a prophylactic treatment for infection by Bacillus anthracis (anthrax). It is also effective against Yersinia pestis and malaria.
Prostaglandines:
Every cell in the body is capable of synthesizing one or more types of PGS. The four major group of PGs are E, F, A, and B.
Pharmacological actions:
stimulation of cyclicAMP production and calcium use by various cells
CVS
PGE2 acts as vasodilator; it is more potent hypotensive than Ach and histamine
Uterous
PGE2 and PGF2α Contract human uterus
Bronchial muscle
PGF2α and thromboxan A2 cause bronchial muscle contraction.
PGE2 & PGI2 cause bronchial muscle dilatation
GIT: PGE2 and PGF2α cause colic and watery diarrhoea
Platelets
Thromboxan A2 is potent induce of platelets aggregation
Kidney
PGE2 and PGI2 increase water, Na ion and K ion excretion (act as diuresis) that cause renal vasodilatation and inhibit
tubular reabsorption
USE
PGI2: Epoprostenol (inhibits platelets aggregation)
PGE1: Alprostadil (used to maintain the potency of arterioles in neonates with congenital heart defects).
PGE2: Dinoproste (used as pessaries to induce labor)
Synthetic analogue of PGE1: Misoprostol (inhibit the secretion of HCl).