What is the pH-partition theory?
Abstract. According to the pH-partition hypothesis the charged species of organic compounds do not contribute to lipid bilayer permeation as they generally show negligible partitioning into n-octanol. With this assumption, membrane permeation is related to the molar fraction of the neutral species at a particular pH.
What are the limitations of pH-partition theory?
Explanation: Some of the deviations of the pH-partition hypothesis are the presence of virtual membrane, absorption of the ionized drug, the influence of GI surface area and residence time, Presence of aqueous unstirred diffusion layer.
What is pH partition theory of drug absorption?
pH PARTITION THEORY The theory states that for drug compounds of molecular weight greater than 100, which are primarily transported across the biomembrane by passive diffusion. o The process of absorption is governed by: 1. The dissociation constant (pKa) of the drug.
What is the significance of pH partitioning in pharmaceutical system?
1957) proposed the pH – partition theory to explain the influence of GI pH and drug pKa on the extent of drug transfer or drug absorption. Brodie reasoned that when a drug is ionized it will not be able to get through the lipid membrane, but only when it is non ionized and therefore has a higher lipid solubility.
Which of the following will influence drug absorption according to pH partition theory?
Drugs are absorbed from the biological membranes by passive diffusion depending on the fraction of un-ionized form of the drug at the pH of that biological membrane. Depends on both their pKa and the solution pH.
How does pH partitioning affect absorption?
pH partition theory of drug absorption is based on the GIT is a simple lipid barrier to the transport of drugs and chemicals. Accordingly the unionized form of an acid or basic drug, if sufficient lipid soluble, is absorbed but the ionized formis not.
How does pH affect drug stability?
In addition to temperature, pH is also a factor that affects the stability of a drug prone to hydrolytic decomposition. Drug stability can frequently be improved though the use of buffering agents between pH 5 and pH 6. Oxidation is another destructive process that produces instability in drug products.
How does pH affect drug distribution?
Urine pH is a great influence on whether a drug is excreted quickly or slowly and in some clinical situations is manipulated to control the excretion of certain drugs from the body. Most drugs are either weak acids or weak bases. In alkaline urine, acidic drugs are more readily ionised.
What is the significance of pH partitioning in pharmaceutical systems?