NEET MDS Lessons
Pharmacology
Oxytetracycline
Treats Oxytetracycline is a medicine used for treating a wide range of infections including infections of the lungs, urinary system, skin and eyes. It may also be used to treat sexually transmitted infections, infections caused by lice, rickettsial infections, cholera and plague. It is very occasionally used to treat leptospirosis, gas gangrene, and tetanus.
Procaine penicillin Procaine penicillin is a combination of benzylpenicillin with the local anaesthetic agent procaine. This combination is aimed at reducing the pain and discomfort associated with a large intramuscular injection of penicillin.
Indications
respiratory tract infections where compliance with oral treatment is unlikely ,syphilis, cellulitis
Aminoglycoside
Aminoglycosides are a group of antibiotics that are effective against certain types of bacteria. They include amikacin, gentamicin, kanamycin, neomycin, netilmicin, paromomycin, streptomycin, and tobramycin. Those which are derived from Streptomyces species
Aminoglycosides work by binding to the bacterial 30S ribosomal subunit, causing misreading of t-RNA, leaving the bacterium unable to synthesize proteins vital to its growth.
Aminoglycosides are useful primarily in infections involving aerobic, Gram-negative bacteria, such as Pseudomonas, Acinetobacter, and Enterobacter. In addition, some mycobacteria, including the bacteria that cause tuberculosis, are susceptible to aminoglycosides. Streptomycin was the first effective drug in the treatment of tuberculosis, though the role of aminoglycosides such as streptomycin and amikacin have been eclipsed (because of their toxicity and inconvenient route of administration) except for multiple drug resistant strains.
Infections caused by Gram-positive bacteria can also be treated with aminoglycosides, but other types of antibiotics are more potent and less damaging to the host. In the past the aminoglycosides have been used in conjunction with penicillin-related antibiotics in streptococcal infections for their synergistic effects, particularly in endocarditis.
Because of their potential for ototoxicity and renal toxicity, aminoglycosides are administered in doses based on body weight. Blood drug levels and creatinine are monitored during the course of therapy.
There is no oral form of these antibiotics: they are generally administered intravenously, though some are used in topical preparations used on wounds.
Aminoglycosides are mostly ineffective against anaerobic bacteria, fungi and viruses.
Beta - Adrenoceptor blocking Agents
These are the agents which block the action of sympathetic nerve stimulation and circulating sympathomimetic amines on the beta adrenergic receptors.
At the cellular level, they inhibit the activity of the membrane cAMP. The main effect is to reduce cardiac activity by diminishing β1 receptor stimulation in the heart. This decreases the rate and force of myocardial contraction of the heart, and decreases the rate of conduction of impulses through the conduction system.
Beta blockers may further be classified on basis of their site of action into following two main classes namely
cardioselective beta blockers (selective beta 1 blockers)
non selective beta 1 + beta 2 blockers
Classification for beta adrenergic blocking agents.
A. Non-selective (β1+β2)
Propranolol Sotalol Nadolol Timolol Alprenolol Pindolol
With additional alpha blocking activity
Labetalol Carvedilol
B. β1 Selective (cardioselective)
Metoprolol Atenolol Bisoprolol Celiprolol
C. β2 Selective
Butoxamine
Mechanisms of Action of beta blocker
Beta adrenoceptor Blockers competitively antagonize the responses to catecholamines that are mediated by beta-receptors and other
adrenomimetics at β-receptors
Because the β-receptors of the heart are primarily of the β1 type and those in the pulmonary and vascular smooth muscle are β2 receptors, β1-selective antagonists are frequently referred to as cardioselective blockers.
β-adrenergic receptor blockers (β blockers)
1. Used more often than α blockers.
2. Some are partial agonists (have intrinsic sympathomimetic activity).
3. Propranolol is the prototype of nonselective β blockers.
4. β blocker effects: lower blood pressure, reduce angina, reduce risk after myocardial infarction, reduce heart rate and force, have antiarrhythmic effect, cause hypoglycemia in diabetics, lower intraocular pressure.
5. Carvedilol: a nonselective β blocker that also blocks α receptors; used for heart failure.
Angiotensin
It is generated in the plasma from a precursor plasma globulin. It is involved in the electrolyte balance, plasma
volume and B.P
Angiotensin I:
Renin is an enzyme produced by the kidney in response to a number of factors including adrenergic activity (β1-
receptor) and sodium depletion. Renin converts a circulating glycoprotein (angiotensinogen) into an inactive material angiotensin-I. It gets activation during passage through pulmonary circulation to angiotensin II by (ACE). ACE is located on the luminal surface of capillary endothelial cells, particularly in the lungs & also present in many organ (e.g brain).
Angiotensin II:
Is an active agent, has a vasoconstrictor action on blood vessels & sodium and water retention
Estimation of the risk of anesthesia (American Society of Anesthesiologists scale)
• ASA 1: healthy patient.
• ASA 2: patient with stable, treated illness like arterial hypertension, diabetes melitus, asthma bronchiale, obesity
• ASA 3: patient with systemic illness decreasing sufficiency like heart illness, late infarct
• ASA 4: patient with serious illness influencing his state like renal insuficiency, unstable hypertension, circulatory insuficiency
• ASA 5: patient in life treatening illness
• ASA 6: brain death- potential organ donor
Needle selection
Nerve blocks:
Inferior alveolar- 25 G short (LLU technique)
PSA- 25 G short
Mental/Incisive- 25 G short
Palatal- 27/30 G short/ultrashort
Gow-Gates/Akinosi- 25 G long
Infraorbital- 25 G long
Field Block:
ASA 25/27 short
Infiltration:
Infiltration/SP 25/27 short
PDL/Intraosseous
PDL 27/30 short
Intraosseous 30 short/ultrashort