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Pharmacology - NEETMDS- courses
NEET MDS Lessons
Pharmacology

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

SYMPATHOMIMETICS 

β2 -agonists are invariably used in the symptomatic treatment of asthma. 

Epinephrine and ephedrine are structurally related to the catecholamine norepinephrine, a neurotransmitter of the adrenergic nervous system 

Some of the important β 2 agonists like salmeterol, terbutaline and salbutamol are invariably used as bronchodilators both oral as well as
aerosol inhalants 

SALBUTAMOL
It is highly selective β2 -adrenergic stimulant h-aving a prominent bronchodilator action.
It has poor cardiac action compared to isoprenaline.


TERBUTALINE
It is highly selective β2  agonist similar to salbutamol, useful by oral as well as inhalational route.


SALMETEROL

Salmeterol is long-acting analogue of salbutamol 

BAMBUTEROL

It is a latest selective adrenergic β2 agonist with long plasma half life and given once daily in a dose of 10-20 mg orally.


METHYLXANTHINES (THEOPHYLLINE AND ITS DERIVATIVES)


THEOPHYLLINE
Theophylline has two distinct action:
smooth muscle relaxation (i.e. bronchodilatation) and suppression of the response of the airways to stimuli (i.e. non-bronchodilator prophylactic effects). 

ANTICHOLINERGICS

Anticholinergics, like atropine and its derivative ipratropium bromide block cholinergic pathways that cause airway constriction.

MAST CELL STABILIZERS

SODIUM CROMOGLYCATE

It inhibits degranulation of mast cells by trigger stimuli. 
It also inhibits the release of various asthma provoking mediators e.g. histamine, leukotrienes, platelet activating factor (PAF) and interleukins (IL’s) from mast cell 

KETOTIFEN
It is a cromolyn analogue. It is an antihistaminic (H1  antagonist) and probably inhibits airway inflammation induced by platelet activating factor (PAF) in primate. 
It is not a bronchodilator. It is used in asthma and symptomatic relief in atopic dermatitis, rhinitis, conjunctivitis and urticaria.

LEUKOTRIENE PATHWAY INHIBITORS

MONTELUKAST

It is a cysteinyl leukotriene receptor antagonist indicated for the management of persistent asthma. 

Tetracycline
Tetracycline is an antibiotic produced by the streptomyces bacterium

Mechanism and Resistance Tetracycline inhibits cell growth by inhibiting translation. It binds to the 30S  ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. This prevents the addition of amino acids to the elongating peptide chain, preventing synthesis of proteins. The binding is reversible in nature.

Example: Chlortetracycline, oxytetracycline, demethylchlortetracycline, rolitetracycline, limecycline, clomocycline, methacycline, doxycycline, minocycline

Source: Streptomyces spp.; some are also semi-synthetic

Spectrum of activity: Broad-spectrum. Exhibits activity against a wide range of Gram-positive, Gram-negative bacteria, atypical organisms such as chlamydiae, mycoplasmas, rickettsiae and protozoan parasites.

Effect on bacteria: Bacteriostatic

Cells become resistant to tetracyline by at least two mechanisms: efflux and ribosomal protection.

Contraindications Tetracycline use should be avoided during pregnancy and in the very young (less than 6 years) because it will result in permanent staining of teeth causing an unsightly cosmetic result.

Tetracyclines also become dangerous past their expiration dates. While most prescription drugs lose potency after their expiration dates, tetracyclines are known to become toxic over time; expired tetracyclines can cause serious damage to the kidneys.

Miscellaneous: Tetracyclines have also been used for non-antibacterial purposes, having shown properties such as anti-inflammatory activity, immunosuppresion, inhibition of lipase and collagenase activity, and wound healing.

Ibuprofen

used to relieve the symptoms of arthritis, primary dysmenorrhoea, fever; and as an analgesic, especially where there is an inflammatory component.

Indications

rheumatoid arthritis, osteoarthritis, juvenile rheumatoid arthritis, primary dysmenorrhoea

fever, relief of acute and/or chronic pain states in which there is an inflammatory component

MOA

inhibition of  cyclooxygenase (COX); thus inhibiting prostaglandin synthesis.

COAGULANTS

An agent that produces coagulation (Coagulation is a complex process by which blood forms clots).

ANTICOAGULANTS

An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting.

 

Anticoagulants:

Calcium Chelators (sodium citrate, EDTA)

Heparin

Dalteparin Sodium (Fragmin) -Low molecular-weight heparin

Enoxaparin - Low molecular-weight heparin

Tinzaparin Sodium  - Low molecular-weight heparin

Warfarin

Lepirudin - recombinant form of the natural anticoagulant hirudin: potent and specific Thrombin inhibitor

Bivalirudin - analog of hirudin: potent and specific Thrombin inhibitor

Procoagulants:

Desmopressin acetate

Antiplatelet Drugs:

Acetylsalicylic Acid, Ticlopidine, Sulfinpyrazone, Abciximab , Clopidogrel bisulfate

Fibrinolytic Drugs:

Tissue Plasminogen Activator (t-PA, Activase), Streptokinase (Streptase),

Anistreplase, Urokinase

 

Antagonists:

Protamine sulfate, Aminocaproic acid

Pharmacological agents used to treat blood coagulation disorders fall in to three major categories:

1. Anticoagulants: Substances that prevent the synthesis of a fibrin network which inhibits coagulation and the formation of arterial thrombi and thromboembolic clots.

2. Antiplatelet agents: Substances that reduce the adhesion and aggregation of platelets.

3. Fibrinolytic agents: Substances that promote the destruction of already formed blood clots or thrombi by disrupting the fibrin mesh.

DOBUTAMINE

It is a derivative of dopamine and has relatively β1 -selective action and it also activates α1 receptors and do not have D1  receptor agonistic property. It increases the force of myocardial contraction and cardiac output without significant change in heart rate, blood pressure and peripheral resistance. It is used as inotropic agent and for short term management of CHF and also in patients who are unresponsive to digitalis.

Sulfonylureas

1st generation
tolbutamide
chlorpropamide

2nd generation

glyburide
glimepiride
glipizide

Mechanism

glucose normally triggers insulin release from pancreatic β cells by increasing intracellular ATP
→ closes K+ channels → depolarization → ↑ Ca2+ influx → insulin release

sulfonylureas mimic action of glucose by closing K+ channels in pancreatic β cells 
→ depolarization → ↑ Ca2+ influx → insulin release

its use results in

↓ glucagon release
↑ insulin sensitivity in muscle and liver

Clinical use

type II DM

stimulates release of endogenous insulin 
cannot be used in type I DM due to complete lack of islet function

Toxicity

first generation

disulfiram-like effects
especially chlorpropamide

second generation

hypoglycemia
weight gain

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