Drug absorption is determined by
the drug’s physicochemical properties, formulation, and route of administration
.
What factors influence absorption?
The oral absorption of any chemical entity reflects a complex spectrum of events. Factors influencing product bioavailability include
drug solubility, permeability, and the rate of in vivo dissolution.
What affects drug absorption?
Drug absorption depends on
the lipid solubility of the drug, its formulation and the route of administration
. A drug needs to be lipid soluble to penetrate membranes unless there is an active transport system or it is so small that it can pass through the aqueous channels in the membrane.
What is the most important factor that affects drug absorption?
Solubility and permeability
are considered as the major physicochemical factor that affect the rate and extent of oral drug absorption, moreover other physicochemical properties always show their effects to drug absorption via affecting solubility and permeability.
What means drug absorption?
The most important principle in pharmacokinetics theory is drug absorption which is defined as
the transportation of the unmetabolized drug from the site of administration to the body circulation system
.
What increases drug absorption?
Physiologically, a drug’s absorption is enhanced
if there is a large surface area available for absorption
(e.g. villi/microvilli of intestinal tract) and if there is a large blood supply for the drug to move down its concentration gradient.
Which is the major process of absorption for more than 90% of drugs?
Passive diffusion or non-ionic diffusion
is considered as the major absorption process for more than 90% of drugs (see figure 3). It is the movement of the drug molecule from a region of higher concentration to a region of lower concentration.
What are the factors affecting drug distribution?
Drug distribution is impacted by several factors related to the drug and the body. The drug-related factors include
blood and tissue binding proteins, pH, and perfusion
. The body-related factors include body water composition, fat composition, diseases (e.g., volume depletion, burns, third spacing).
What medication route has the slowest absorption rate?
Subcutaneous (SC)
The absoroption of subcutaneous injections is slower than that of IV route and it needs absorption similar to Intramuscular injection.
What factors can influence the pharmacokinetics of a drug?
Pharmacokinetics can vary from person to person and it is affected by age,
gender, diet, environment, body weight and pregnancy
, patient’s pathophysiology, genetics and drug- drug or food-drug interactions.
What route of drug absorption has the greatest bioavailability?
The intravenous route
provides 100% absorption and bioavailability and is the least problematic of routes of administration.
Which factor affects the absorption of drugs from Git?
| Drug factors: | Concentration A large drug dose will be absorbed more rapidly because of the high concentration gradient | Gastrointestinal factors | Gastric motility Gastric emptying is the major determinant of absorption |
|---|
How route of administration affects drug absorption?
Oral route
For drugs administered orally, absorption may begin in the mouth and stomach. However, most drugs are usually absorbed from the small intestine. The drug passes through the intestinal wall and travels to the liver before being transported via the bloodstream to its target site.
Does food affect drug absorption?
Food intake exerts a
complex influence on the bioavailability of drugs
. It may interfere not only with tablet disintegration, drug dissolution and drug transit through the gastrointestinal tract, but may also affect the metabolic transformation of drugs in the gastrointestinal wall and in the liver.
Why does blood flow affect absorption of drugs taken orally?
Local blood flow is a strong determinant of the rate of absorption
because it continuously maintains the concentration gradient necessary for passive diffusion to occur
. For orally administered drugs, remember that the blood supply draining the gut passes through the liver before reaching the systemic circulation.
Where does drug absorption occur?
Because most absorption occurs in
the small intestine
, gastric emptying is often the rate-limiting step. Food, especially fatty food, slows gastric emptying (and rate of drug absorption), explaining why taking some drugs on an empty stomach speeds absorption.
