🔴 DEFINITION

Suspension =

Suspension is a heterogeneous mixture in which the solute particles do not dissolve, but get suspended throughout the bulk of the solvent, left floating around freely in the medium.

🔴 DEFINITION

Flocculated System =

The system in which supernatant quickly becomes clear due to rapid rate of sedimentation.

🔴 DEFINITION

Deflocculated System =

The system in which supernatant will remain cloudy due to slow rate of sedimentation.

🔴Classification of Pharmaceutical Suspensions

🔺1. Based on General Classes

 Oral suspension

 Externally applied suspension

 Parenteral suspension

🔺2. Based on Proportion of Solid Particles

 Dilute suspension (2 to10%w/v solid)

 Concentrated suspension (50%w/v solid)

🔺3. Based on Electro Kinetic Nature of Solid

 Particles

 Flocculated suspension

 Deflocculated suspension

🔺4. Based on Size of Solid Particles

 Colloidal suspension (< 1 micron)

 Coarse suspension (>1 micron)

 Nano suspension (10 ng)

🔴RECEPTORS

🔵TYPES OF RECEPTORS
🔸ION CHANNEL RECEPTORS(Ligand gated ion channel)
🔸G-PROTEN COUPLED RECEPTORS (GPCR'S)
🔸ENZYME LINKED RECEPTORS
🔸NUCLEAR RECEPTORS

📌ION CHANNEL RECEPTORS

♦️MECHANISM :

▪ Ligand-gated ion channels are integral membrane proteins that contain a pore which allows the regulated flow of selected ions across the plasma membrane.
▪Ion flux is passive and driven by the electrochemical gradient for the permeant ions.
▪ The channels are opened, or gated, by the binding of a neurotransmitter to an orthosteric site(s) that triggers a conformational change that results in the conducting state.
▪ Modulation of gating can occur by the binding of endogenous, or exogenous, modulators to allosteric sites.
It mediate fast synaptic transmission, on a millisecond time scale, in the nervous system and at the somatic neuromuscular junction..
▪Such transmission involves the release of a neurotransmitter from a pre-synaptic neurone and the subsequent activation of post-synaptically located receptors that mediate a rapid, phasic, electrical signal (the excitatory, or inhibitory, post-synaptic potential).

EXAMPLES
1. Nicotinic Receptor-Nm, Nn
2.5HT3 Receptor
3.GABA-A Receptor
4.NMDA Receptor

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🔴Definitions:

🔸Emulsions:
-They are biphasic liquid systems consisting of two immiscible liquid phases. These phases are present in such as way that one phase is dispersed in the other continuous phase. Emulsions are part of a more general class of two-phase systems of matter called colloids.

🔸Flocculation :
-When the particles or droplets of the dispersed phase aggregate together on account of attractive forces, the phenomenon is known as flocculation and results in an unstable system. Flocculation is mainly observed in case of oil in water type of emulsions.

🔸Coalescence :
-When the droplets of discontinuous phase bump into each other to form a larger droplet thus increasing the average particle size over time, it is known as coalescence which is a form of instability.

🔸Creaming :
-When the droplets in an emulsion rise to the top of the emulsion under the influence of buoyancy or centripetal force, it results in the creaming of emulsion.

🔸Ostwald Ripening:
-It describes the change of an inhomogeneous structure over time, i.e., small crystals or sol particles dissolve and redeposit onto larger crystals or sol particles. Ostwald ripening is generally found in water-in-oil emulsions.

🔴Mechanisms of Emulsification

A number of different chemical and physical processes and mechanisms can be involved in the process of emulsification.

🔸Surface tension theory :
-According to this theory, emulsification takes place by the reduction of interfacial tension between two phases.

🔸Repulsion theory:
-The theory proposes that the emulsifying agent creates a film over one phase that forms globules, which repel each other. This repulsive force causes them to remain suspended in the dispersion medium.

🔸Viscosity modification:
-Certain emulgents such as acacia, tragacanth, carboxymethylcellulose, polyethylene glycol, increase the viscosity of the medium, which helps create and maintain the suspension of globules of the dispersed.

🔴MECHANISM

📌G-PROTEIN COUPLED RECEPTOR

▪G protein-coupled receptors (GPCRs), also known as seven transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionary related proteins that are cell surface receptors that detect molecules outside the cell and activate cellular responses. ▪Coupling with G proteins, they are called seven-transmembrane receptors because they pass through the cell membrane seven times.
▪ Ligands can bind either to extracellular N-terminus and loops or to the binding site within transmembrane helices .
▪They are all activated by agonists although a spontaneous auto-activation of an empty receptor can also be observed.
The G-protein coupled receptors expressed in three different ways
▪Gs-Increses the level of CAMP
▪Gi-Decreses levels of CAMP
▪Gq-Increses IP3 DAG

🔸There are two principal signal transduction pathways involving the G protein-coupled receptors:

1.The cAMP signal pathway and

2.The phosphatidylinositol signal pathway.

▪When a ligand binds to the GPCR it causes a conformational change in the GPCR, which allows it to act as a guanine nucleotide exchange factor (GEF).
▪The GPCR can then activate an associated G protein by exchanging the GDP bound to the G protein for a GTP. ▪The G protein's α subunit, together with the bound GTP, can then dissociate from the β and γ subunits to further affect intracellular signaling proteins or target functional proteins directly depending on the α subunit type.

🔴Classification :-
Pharmaceutical Emulsions

🔺1.Simple emulsions

Oil-in-Water (O/W)
Water-in-Oil (W/O)

🔺2.Multiple emulsions

Oil-in-Water-in-Oil
(O/W/O)
Water-in-Oil-in-Water
(W/O/W)

🔺3.Micro emulsions

🔴 Types of Emulsion :-
-Depending upon the nature of the dispersed phase, the emulsions are classified as;

1️⃣ Oil-in-water emulsions (O/W) :

-The emulsion in which oil is present as the dispersed phase and water as the dispersion medium (continuous phase) is called an oil-in-water emulsion. Milk is an example of the oil-in-water type of emulsion. In milk liquid fat globules are dispersed in water. Other examples are, vanishing cream etc.

2️⃣ Water-in-oil emulsion (W/O) :
-The emulsion in which water forms the dispersed phase, and the oil acts as the dispersion medium is called a water-in-oil emulsion. These emulsion are also termed oil emulsions. Butter and cold cream are typical examples of this types of emulsions. Other examples are cod liver oil etc.

🔴ADR:

IDIOSYNCRASY-
•Genetically determined abnormal reactivity to a chemical.
•Certain Bizzare drug effects due to peculiarities of an individual,not found in majority subjects,and produces the uncharacteristic reaction.

E.g.-
•Barbiturates---> Excitment and mental confusion in some individuals.
•Quinine--->Cramps,diarrhea, asthma,vascular collapse in some individuals.
•Chloramphenicol--->Aplastic anemia in rare individuals.