NEET MDS Lessons
Pharmacology
Thiazide diuretics
Chlorothiazide, Hydrochlorothiazide
Mechanism(s) of Action
1. Block facilitated Na/Cl co-transport in the early distal tubule. This is a relatively minor Na absorption mechanism and the result is modest diuresis
2. Potassium wasting effect
a. Blood volume reduction leads to increased production of aldosterone
b. Increased distal Na load secondary to diuretic effect
c. a + b = increase Na (to blood) for K (to urine) exchange which produces indirect K wasting
3. Increase distal Ca re-absorption (direct effect)
o causes an increase in plasma calcium.This is unimportant NORMALLY but makes thiazides VERY inappropriate choice for hypercalcemic patients.
4. Anti-diuretic effect in nephrogenic diabetes insipidus patients secondary to depletion of Na and Water.
Toxicity
• Electrolyte imbalance (particularly hypokalemia) ,Agranulocytosis , Allergic reactions
• Hyperuricemia , Thrombocytopenia
Itraconazole:
The drug may be given orally or intravenously.
PSEUDOEPHEDRINE
Pseudoephedrine appears to have less pressor activity and weaker central nervous system effects than ephedrine. It has agonist activity at both β1 and β2 adrenoceptors, leading to increased cardiac output and relaxation of bronchial smooth muscle.
Pseudoephedrine is rapidly absorbed throughout the body. It is eliminated largely unchanged in urine by N-demethylation.
It is indicated in symptomatic relief from stuffed nose, respiratory tract congestion, bronchospasm associated with asthma, bronchitis and other similar disorders.
Classification Based on
a. Chemical structure
I. Sulphonamidcs.and others - c.g.. sulphadiazine. etc.
2. Beta-lactum ring - e.g.. penicillin
3. Tetracycline - e.g.. Oxytetracycline,.doxycycline.etc.
b. Mechanism of action
1. Inhibits cell-wall synthesis - penicillin. cephalosporin..cycloserine. etc.
2. Cause leakage from cell-membrane – polypeptides (polymyxin, Bacitracin), polyenes (Nystatin)
3. Inhibit protein synthesis - tetracyclines. chloramphenicols. erythromycin.
4. Cause mis-reading of mRNA code - aminoglycosides
5. Interfere with DNA function - refampicin.. metronidazole
6. Interfere with intermediary metabolism - sulphonamides. ethambutole
c. Type of organism against which it is primarily activate
I. Antibacterial - penicillin.
2. Antifungal - nystatin.
d. Spectrum of activity
1. Broad spectrum - tetracylines .
2. Narrow spectrum - penicillin G (penG). streptomycin.erythromycin
e. Type of action
I. Bacteriostatic - sulphonamides, erythromycin.tertracyclines
2. Bacteriocidal - penicillin. aminoglycoside
f. Source
I. Fungi - penicillin. cephalosporins
2. Bacteria - Polymyxin B
Loperamide
- Similar chemically and pharmacologically to Diphenoxylate.
- Slows gastrointestinal motility by effects on the circular and longitudinal muscles of the intestine.
- Not well absorbed following oral administration.
- Useful in the treatment of diarrhea.
Class III Potassium Channel Blockers
Prolong effective refractory period by prolonging Action Potential
Treatment: ventricular tachycardia and fibrillation, conversion of atrial fibrillation or flutter to sinus rhythm, maintenance of sinus rhythm
– Amiodarone (Cordarone) – maintenance of sinus rhythm
– Bretylium (Bretylol)
– Ibutilide (Corvert)
– Dofetilide (Tykosyn)
– Sotalol (Betapace)
Amiodarone
- Has characteristics of sodium channel blockers, beta blockers, and calcium channel blockers
- Has vasodilating effects and decreases systemic vascular resistance
- Prolongs conduction in all cardiac tissue
- Decreases heart rate
- Decreases contractility of the left ventricles
Class III - Adverse Effects
- GI- Nausea vomiting and GI distress
- CNS- Weakness and dizziness
- CV-Hypotension, CHF, and arrhythmias are common.
- Amiodarone associated with potentially fatal Hepatic toxicity, ocular abnormalities and serious cardiac arrhythmias.
Drug – Drug Interactions
These drugs can cause serious toxic effects if combined with digoxin or quinidine.
Methods of general anesthesia
CIRCLE SYSTEM
*HIGH-FLOW
FRESH GAS FLOW > 3 l/min.
*LOW-FLOW
FGF ok. 1l/min.
*MINIMAL-FLOW
FGF ok. 0,5 l/min.