I wanted to know can there be / is there a compound which by itself has a very low bio-accessibility but when given with other compounds increases bio-availability of that compound?
There are many reasons why a drug has low oral bioavailability. A major one is poor aqueous solubility. Hence if we can improve the solubility for example using a suitable salt form then we may be able to increase the bioavailability. Other methods include forming a more soluble complex for example with cyclodextrins, using a more soluble polymorphic form or amorphous form of the drug. Drugs in the form of liquids such as vitamin E has low and erratic bioavailability under fasted state and hence should be taken after a meal or formulated as a self emulsifying system which can mimic the intraluminal processing when taken with a meal. Certain compounds are not stable in the harsh gastric environment where the pH is near 1. In this case an enteric coat is useful. Also, some drugs are affected by the absorption barrier comprising P-gP and CYP3A4. The former is a counter transport protein that expels the drug back into the lumen of the GIT whereas CYP3A4 is a metabolizing enzyme that metabolizes a wide variety of drugs. Both act synergistically a s barrier to the absorption of many drugs but both are saturable. Hence if we administer 2 compounds which a substrates of both P-gP and CYP3A4, absorption of both can be enhance if the system is saturated. Piperine may also increase the absorption of certain compounds (mentioned by someone else above) but not helpful to others.
Yes, there are many. One example immediately comes to mind. Check out "Piperine enhances the bioavailability of the tea polyphenol (-)-epigallocatechin-3-gallate in mice."
Technically that goes for many hydrophobic compounds. Bioavailability depends on a variety of factors one of them being aqueous solubility. Hydrophobic compounds by their nature are insoluble and therefore "biounavailable". One very clear example is Vitamin D. On its own it is very difficult to dissolve it water however it is necessary for calcium absorption in the gut. It is for this reason you will find that vitamin D is fortified using an emulsion system that improves its bioavailability which then improves calcium absorption.
Have a look at cyclodextrins which could enhance bioavailability and which have poor bioavailability
It depends on the nature of drug and its site of action. For example levodopa acts in brain and its bioavailability is enhanced by carbidopa which by itself poorly crosses the blood-brain barrier.
Nanoparticles plays vital role. Find enclosed an article which may help you a bit.
There are many reasons why a drug has low oral bioavailability. A major one is poor aqueous solubility. Hence if we can improve the solubility for example using a suitable salt form then we may be able to increase the bioavailability. Other methods include forming a more soluble complex for example with cyclodextrins, using a more soluble polymorphic form or amorphous form of the drug. Drugs in the form of liquids such as vitamin E has low and erratic bioavailability under fasted state and hence should be taken after a meal or formulated as a self emulsifying system which can mimic the intraluminal processing when taken with a meal. Certain compounds are not stable in the harsh gastric environment where the pH is near 1. In this case an enteric coat is useful. Also, some drugs are affected by the absorption barrier comprising P-gP and CYP3A4. The former is a counter transport protein that expels the drug back into the lumen of the GIT whereas CYP3A4 is a metabolizing enzyme that metabolizes a wide variety of drugs. Both act synergistically a s barrier to the absorption of many drugs but both are saturable. Hence if we administer 2 compounds which a substrates of both P-gP and CYP3A4, absorption of both can be enhance if the system is saturated. Piperine may also increase the absorption of certain compounds (mentioned by someone else above) but not helpful to others.
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