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Pharmacology - NEETMDS- courses
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Pharmacology

Neuron Basic Structure (How brain cells communicate)

• Synapse:A junction between the terminal button of an axon and the membrane of another neuron
• Terminal button(orbouton):The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron.
• Neurotransmitter:A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron.

Different types of Synapses
1-Axo-denrdritic 
2-Axo-axonal 
3-Axo-somatic

Chemical transmission in the CNS 


The CNS controls the main functions of the body through the action endogenous chemical substances known as “neurotransmitters”.
These neurotransmitters are stored in and secreted by neurons to “transmit”information to the postsynaptic sites producing either excitatoryor inhibitory responses.
Most centrally acting drugs exert their actions at the synaptic junctions by either affecting neurotransmitter synthesis, release, uptake, or by exerting direct agonistor antagonistaction on postsynaptic sites.

Ketoconazole

synthetic antifungal drug

used for infections such as  athlete's foot, ringworm, candidiasis (yeast infection or thrush), jock itch.

Ketoconazole is used to treat eumycetoma, the fungal form of mycetoma.

MOA: Ketoconazole is imidazole structured, and interferes with the fungal synthesis of  ergosterol, the main constituent of cell membranes, as well as certain enzymes. It is specific for fungi, as mammalian cell membranes contain no ergosterol.

Sensitive fungi Ketoconazole inhibits growth of  dermatophytes and  yeast species (such as Candida albicans).

Antiarrhythmic Drugs

Cardiac Arrhythmias 
Can originate in any part of the conduction system or from atrial or ventricular muscle.
Result from
– Disturbances in electrical impulse formation (automaticity) 
– Conduction (conductivity) 
– Both

MECHANISMS OF ARRHYTHMIA
ARRHYTHMIA – absence of rhythm
DYSRRHYTHMIA – abnormal rhythm

ARRHYTHMIAS result from:
1. Disturbance in Impulse Formation
2. Disturbance in Impulse Conduction
- Block results from severely depressed conduction
- Re-entry or circus movement / daughter impulse

Types of Arrhythmias

• Sinus arrhythmias 
– Usually significant only 
– if they are severe or  prolonged 

• Atrial arrhythmias 
– Most significant in the presence of underlying heart disease
– Serious: atrial fibrillation can lead to the formation of clots in the heart 

• Nodal arrhythmias 
– May involve tachycardia and increased workload of the heart or bradycardia from heart block 

• Ventricular arrhythmias 
– Include premature ventricular contractions (PVCs), ventricular tachycardia, and ventricular fibrillation 

Class

Action

Drugs

I

Sodium Channel Blockade

 

  IA

Prolong repolarization
lengthen AP duration
Intermediate interaction with Na+ channels

Quinidine, procainamide, disopyramide

  IB

Shorten repolarization
shorten AP duration
rapid interaction with Na+ channels

Lidocaine, mexiletine, tocainide, phenytoin

  IC

Little effect on repolarization
no effect or minimal ↑ AP duration
slow interaction with Na+ channels

Encainide, flecainide, propafenone

II

Beta-Adrenergic Blockade

Propanolol, esmolol, acebutolol, l-sotalol

III

Prolong Repolarization (Potassium Channel Blockade; Other)

Ibutilide, dofetilide, sotalol (d,l), amiodarone, bretylium

IV

Calcium Channel Blockade

Verapamil, diltiazem, bepridil

Miscellaneous

Miscellaneous Actions

Adenosine, digitalis, magnesium

 

Indications
• To convert atrial fibrillation (AF) or flutter to normal sinus rhythm (NSR) 
• To maintain NSR after conversion from AF or flutter 
• When the ventricular rate is so fast or irregular that cardiac output is impaired
– Decreased cardiac output leads to symptoms of decreased systemic, cerebral, and coronary circulation 
• When dangerous arrhythmias occur and may be fatal if not quickly terminated 
– For example: ventricular tachycardia may cause cardiac arrest 

Mechanism of Action 
• Reduce automaticity (spontaneous depolarization of myocardial cells, including ectopic pacemakers) 
• Slow conduction of electrical impulses through the heart
• Prolong the refractory period of myocardial cells (so they are less likely to be prematurely activated by adjacent cells 
 

Sedative-Hypnotic Drugs

Sedative drug is the drug that reduce anxiety (anxiolytic) and produce sedation and referred to as minor tranquillisers. 

Hypnotic drug is the drug that induce sleep


Effects: make you sleepy; general CNS depressants

Uses: sedative-hypnotic (insomnia ), anxiolytic (anxiety, panic, obsessive compulsive, phobias), muscle relaxant (spasticity, dystonias), anticonvulsant (absence, status epilepticus, generalized seizures—rapid tolerance develops), others (pre-operative medication and endoscopic procedures,  withdrawal from chronic use of ethanol or other CNS depressants)

1- For panic disorder alprazolam is effective.

2- muscle disorder: (reduction of muscle tone and coordination) diazepam is useful in treatment of skeletal muscle spasm e.g. muscle strain and spasticity of degenerative muscle diseases.

3-epilepsy: by increasing seizure threshold.

Clonazepam is useful in chronic treatment of epilepsy while diazepam is drug of choice in status epilepticus.

4-sleep disorder: Three BDZs are effective hypnotic agents; long acting flurazepam, intermediate acting temazepam and short
acting triazolam. They decrease the time taken to get to sleep They increase the total duration of sleep

5-control of alcohol withdrawals symptoms include diazepam, chlordiazepoxide, clorazepate and oxazepam.

6-in anesthesia: as preanesthetic amnesic agent (also in cardioversion) and as a component of balanced anesthesia

Flurazepam significantly reduce both sleep induction time and numbers of awakenings and increase duration of sleep and little rebound insomnia. It may cause daytime sedation.

Temazepam useful in patients who experience frequent awakening, peak sedative effect occur 2-3 hr. after an oral dose.

Triazolam used to induce sleep in recurring insomnia and in individuals have difficulty in going to sleep, tolerance develop within few days and withdrawals result in rebound insomnia therefore the drug used intermittently.


Drugs and their actions

1. Benzodiazepines: enhance the effect of gamma aminobutyric acid (GABA) at GABA receptors on chloride channels. This increases chloride channel conductance in the brain (GABA A A receptors are ion channel receptors).

2. Barbiturates: enhance the effect of GABA on the chloride channel but also increase chloride channel conductance independently of GABA, especially at high doses 

3. Zolpidem and zaleplon: work in a similar manner to benzodiazepines but do so only at the benzodiazepine (BZ1) receptor type. (Both BZ1and BZ2 are located on chloride channels.)

4. Chloral hydrate: probably similar action to barbiturates.

5. Buspirone: partial agonist at a specific serotonin receptor (5-HT1A).

6. Other sedatives (e.g., mephenesin, meprobamate, methocarbamol, carisoprodol, cyclobenzaprine): 
mechanisms not well-described. Several mechanisms may be involved.

7. Baclofen: stimulates GABA linked to the G protein, Gi , resulting in an increase in K + conductance and a decrease in Ca2+ conductance. (Other drugs mentioned above do not bind to the GABA B receptor.) 

8. Antihistamines (e.g., diphenhydramine): block H1 histamine receptors. Doing so in the CNS leads to sedation.

9. Ethyl alcohol: its several actions include a likely effect on the chloride channel.

Balanced Anesthesia
A barbiturate, narcotic analgesic agent, neuromuscular blocking agent, nitrous oxide and one of the more potent inhalation anesthetic.

Sufentanil

  • A synthetic opioid related to fentanyl.
  • About 7 times more potent than fentanyl.
  • Has a slightly more rapid onset of action than fentanyl.

ANTIBIOTICS

Chemotherapy: Drugs which inhibit or kill the infecting organism and have no/minimum effect on the recipient.

Antibiotic these are substances produced by microorganisms which suppress the growth of or kill other micro-organisms at very low concentrations.

Anti-microbial Agents: synthetic as well as naturally obtained drugs that attenuate micro-organism.

 

SYNTHETIC ORGANIC ANTIMICROBIAL DRUGS

Sulfonamides

Trimethoprim-sulfamethoxazole

Quinolones – Ciprofloxacin

ANTIBIOTICS THAT ACT ON THE BACTERIAL CELL WALL

Penicillins

Cephalosporins

Vancomycin

INHIBITORS OF BACTERIAL PROTEIN SYNTHESIS

Aminoglycosides - Gentamicin

Antitubercular Drugs: Isoniazid & Rifampin

Tetracyclines

Chloramphenicol

Macrolides – Erythromycin, Azithromycin

Clindamycin

Mupirocin

Linezolid

 ANTIFUNGAL DRUGS

Polyene Antibiotics (Amphotericin B, Nystatin and Candicidin)

Imidazole and Triazole Antifungal Drugs

Flucytosine

Griseofulvin

ANTIPROTOZOAL DRUGS

Antimalarial Drugs – Quinine, Chloroquine, Primaquine

Other Antiprotozoal Drugs – Metronidazole, Diloxanide, Iodoquinol

 ANTIHELMINTHIC DRUGS

Praziquantel

Mebendazole

Ivermectin

ANTIVIRAL DRUGS

Acyclovir

Ribavirin

Dideoxynucleosides

Protease inhibitors

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