الاثنين، 17 يناير 2011

receptors

drugs is potent , specific due to high affinity of it to bind with receptors
definitions :
pharmacokinetics : 
what body do to the drug include : absorption , distribution , metabolism , excretion 
pharmacodynamic :
what drug do to body include action , mechanism of action , adverse effect
receptors :
protein macromolecule on the surface of cell that react with specific substance to initiate effect
agonist : 
drug that cause response by interacting with reseptor , has affinity and efficacy
affinity :
ability of agonist ro bind the receptors then form drug receptor complex
efficacy :
ability of drug receptor complex to cause response
antagoinst :
drug compete with agonist by blocking the receptor , has affinity but no efficacy
partial ahonist :
drug have affinity with moderate efficacy 

types of receptors :
1- ligand gates ionic channels :
Fast (millisecond responses) neurotransmitters (e.g.
nicotinic receptors), linked directly to a transmembrane
ion channel.

2- G-protein
 Slower neurotransmitters and hormones (e.g. muscarinic
receptors) linked to an intracellular G-protein (‘GPCR’).

3- tyrosine kinase linked receptors 
insulin receptors) are slower still.

4- receptors that regulate DNA transcription 
intracellular , gene transcription

الأحد، 16 يناير 2011

parmacodynamic 2

3 - metabolsim - biotransformation :
chemical alternation of drugs aiming to convert active lipophilic non-ionized drug to inactive hydrophilic ionized easily excreted metabolites
metabolism of drugs under go two phases - not always - but common
types :
a- phase 1 : non-synthetic " include
1- oxidation
2- reduction
3- hydrolysis

results oh this phase :
- convert inactive drugs to active drug 
- convert active drug to active metabolites as phenacetin to paracetamol
- convert active drug to inactive metabolites as acetyl-choline to acetic acid

b- phase 2 : synthesis " conjugation 
convert the drug to conjugation which is inactive , more water soluble
Molecules or groups
involved in phase II reactions include acetate, glucuronic acid,
glutamine, glycine and sulphate, which may combine with
reactive groups introduced during phase I metabolism (‘functionalization’)


site of biotransformation :

1- hepatic microsomal enzymes 
there are drugs induce by increase activity of hepatic enzyme so increase degardation of drug 
inducers : rifampicin , phenytoin , smoker , androgens
inhibitors : chloramphenicol , estrogen , progesterone , diazepam 

2- non-microsoaml drug biotransformation :
digestive juices , palsma , flora

pharmacodynamic

1- adrenoceptors were divided first into α and β, then subdivided
into α1/α2 and β1/β2. Many other useful receptor classifications,
including those of cholinoceptors, histamine receptors, serotonin
receptors, benzodiazepine receptors, glutamate receptors
and others have been proposed on a similar basis.

2- dose ratio is If a dose (C) of agonist causes a defined effect when
administered alone, then the dose (C ) needed to produce the
same effect in the presence of antagonist .

3- Bioavailability of a drug is measuring concentration vs. time
curves following administration of the preparation via its
intended route (e.g. orally) and of the same dose given intravenously
(i.v.).

4- prodrug is One approach to improving absorption or distribution to a relatively
inaccessible tissue (e.g. brain) is to modify the drug
molecule chemically to form a compound that is better
absorbed and from which active drug is liberated after absorption.

5- Metronidazole is well absorbed when administered
rectally, and is less expensive than intravenous preparations.

6- 

الخميس، 13 يناير 2011

Randoms -1


1- caries Radiolocence of tooth on X-ray when is exceed 500 um .

2- normal height of alveolar crest of bone is 0,5 - 2 mm below CEJ , and parallel to line drawn between two adjacent CEJ in posterior teeth , while in anterior teeth the crest is pointed . 

3 - radiographic changes occur in periodontal diseases after 6 - 8 months of start disease .

4 - radiographic evaluation of periodontal diseases is based on inter-dental septa , because buccal & lingual bone is obscure by dense roots .

5 - bite-wing is better than peri-apical film in evaluation of periodontal disorders . 

6 - early S & S of periodontal disorder can be only detected clinically . 

7 - the differnt between acutiual alveolar crest height & radiographic apperance is range between 0 - 1.6 mm , according to angulation of the X-ray .

8 - present of intact crestal lamina dura is an indictor for healthy periodentism , while unhealthy one has less diagnostic value , as it can appear unhealthy  but with mild periodonitis .