Biopharmaceutics

the amorphous form is always more stable then the crystal form

Enter the systemic circulation to exert a therapeutic effect

absorption

• The rate or time to dissolve in fluids at the site of absorption
• Absorption of drug into blood circulation

When a diffusion layer, stagnant layer is formed around the solid drug then mixed with the gastric juices to for the bulk of the solution then can get absorbed into the blood stream

• Also called surface renewal theory
• Accounts for packet that are present in the agitated fluid which reach the solid-lquid interface, absorb the solute by diffusion and carry it into the bulk of the solution
• Continuously being replaced by new ones and exposed to new solid surface each time

this number indicates how readily a chemical can dissolve in fats and oils. If the octanol/water partition coefficient is high, e.g. for DDT it is about 6, then the chemical can accumulate more readily in body fat and can be stored there for a very long time, as it may be excreted very slowly

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They are going to absorbed at a pH of their pka. If it is enteric coated and they are acidic they will not be released until the intestines, there will be a small amount of unionized and can diffuse accross the membrane then reset the equilibrium and repeat the process to slowly release an acidic drug in an a basic environment

• Alter drug absorption
• Enhance solubility
• Increase retention time of drug in the GIT
• Act as carriers to increase diffusion across intestinal wall

INcreases bulk

Makes the diluent adhere to the tablet to form a compact mass

Swells up and disintegrates causing a release of active ingredients into solution

improve the flow properties, mainly during manufacturering

Decrease interfacial tension

capable of being percieved by more than one sense organ

the movement of drug between blood and tissues

• Blood flow: rate of delivery to tissues
• Capilary permeability: ability of drug to pass through capillaries
• Binding of drugs to proteins and tissue components
• Hepatic first past effect
• Enterohepatic cycling

• Perfusion is the process of nutritive delivery of arterial blood to a capillary bed
• THe rate of blood flow to certain organs can limited distribution to the target organ
• High Lipid solubility
• Low water solubility

• drugs with charges unable to diffuse across the membranes
• Low lipid solubility
• High water solubility

It is a dose that binds to the plasma protein such that it allows for the actual dose to get to the target tissue

Enterohepatic circulation refers to the circulation of biliary acids from the liver, where they are produced and secreted in the bile, to the small intestine, where it aids in digestion of fats and other substances, back to the liver.

• Enterohepatic circulation also means that some molecules which would not otherwise be very toxic can become extremely hepatotoxic as they reach unexpectedly high hepatic concentrations. Drugs may remain in the enterohepatic circulation for a prolonged period of time as a result of this recycling process.
• When taken with food increases the circulation of drug and can stay in stomach longer
• Fat solubile drugs stays into body longer than water soluble drugs

• F
• Can be secreted through sweat, milk, hair....

• Allows drugs to pass into urine
• Reduced by plasma protein binding
• Only a portion of plasma is filtered

active carrier process for cations and anions

Probenecid

Of lipid soluble drugs back into body across the tubule cells

Glomular filtration

some drugs that are weak acids or weak bases undergo active tubular secretion by transport systems located in the proximal tubular cells

• Most substance can be reabsorbed if they are unionized and lipid soluble
• Manipulation of urine pH makes drugs not to be reabsorbed in overdose situations

Excretion rate divided by plasma drug concentration in units of L/h