Factors That Affect The Rate Of Drug Distribution

*Rectal administration – Medicines administered into the body by this route are absorbed very quickly. Suppositories are available for this route of administration and are inserted high into the rectum.

The route in which a medication is administered is the ‘path’ that the drug/substance/fluid/poison is taken into the body these include:-

The National Prescribing Centre recognize some fundamental differences in the absorption, distribution and excretion of medicines between adults and children. The differences are published in the National Prescribing Centre’s bulletin, produced by

Absorption – “How the drugs enter the circulation process through the body, and how they resist general breakdown by the stomach, liver, and the intestines”. Some of the factors that affect the absorption of drugs in the body is as follows, “acidity of the stomach, Physiochemical properties, Presence of food in the stomach or intestine, and Routes of administration”,

enters the blood stream in just a matter of seconds of using this drug. When eating or drinking

Pharmacokinetics consists of three components, absorption, distribution, and clearance. Absorption, especially from the oral route is the least influenced by the aging process and slows down, but remains complete (Adams et al., 2011). As the number of drugs ingested increases, the risk that absorption is interrupted increases (Adams et al., 2011). Distribution is significantly impacted with age. Older people have more body fat and less water than younger people. As a result, a drug that is fat soluble will remain in older bodies

Either of these allow it to circulate throughout the entire circulatory system. This allows the drug/toxin to be distributed throughout the body to the different compartments including tissues. The distribution of drug/toxin decreases the plasma concentration of the drug. This means that the ratio that describes volume of distribution, amount administered (a) over the plasma concentration of the drug/toxin ([p]), would be very large because the amount administered would be bigger by X number of magnitude, where X > 1 but would most often be somewhere along the lines of 10 or more, compared to the plasma concentration of the drug/toxin. This in turn would mean that the volume of distribution is very large for a drug/toxin that meet these characteristics. A good example of this type of drug/toxin would be lead (Pb). Roughly 99% of lead in the blood is found to be bound to red blood cells, meaning that only 1% of lead in the blood is found in plasma, which allows for the relegation of lead into other compartments in the body during circulation (Holstege et el.,

This subject interest me because when I was younger I was struck by a truck and while in the hospital I asked the nurse what medication they were using for pain management. She said she was using a water solution to be administered by IV because I had lost a lot of blood and fluids. I wondered why do I need more fluids and why it had to be administered by vein instead of the mouth. She sums it up to that the medications couldn’t be taken by mouth because the doctors need to had to make sure the liquid enter in the bloodstream and that it reacted quickly. Ever since then I always asked how these medications break down in the body to perform a specific task. I believe that I am suitable for this course because I have believed I have great problem-solving skills and scientific

After oral administration, tacrolimus is absorbed rapidly in most patients and reaches its peak plasma/blood concentration in 30 minutes to one hour. While in some patients it is absorbed slowly over a prolonged period, resulting in a flat absorption profile. Tacrolimus has a large variability in the rate of absorption and absolute bioavailability between individuals. It ranges from 5%–93% and approximately 25% of the oral dose is bioavailable due to an active barrier to drug absorption (Venkataramanan et al., 1995). The poor water solubility of tacrolimus and reduced gut motility in transplant recipients is responsible for the poor and erratic absorption of tacrolimus. Since tacrolimus is well-known as a substrate of CYP3A iso-enzymes, its poor bioavilability is to a large extent caused by presystemic metabolism of tacrolimus in the gut wall and liver (Tuteja et al., 2001).

As doses shift from low to high, the relative importance of individual enzymes involved in the metabolism may also shift. For example, at the high dose, oxon formation correlated best the CYP3A4 activity, while at the low dose, oxon formation correlated best with the higher affinity enzyme CYP2B6. Nutrition plays a role in metabolism(Croom, 2012). Poor nutrition limits the available energy for metabolism. Metabolizing enzymes require cofactors and micronutrients that may be lost with inadequate nutrition. Food itself can change the amount of xenobiotic available for metabolism by affecting its solubility, as well as by altering gastric emptying and bioavailability(Croom, 2012). Oral exposures involve first-pass metabolism, where the bulk of the blood collected from gastrointestinal tract first passes through the liver before being transported to the rest of the body(Croom, 2012). For xenobiotics with significant dermal absorption or significant exposure through inhalation, this can dramatically increase the amount available in the circulation and if the target organ is capable of bioactivation result in significant toxicity in that

The different ways that drugs get into the body is by oral administration, injection, inhalation and absorption through the skin. Oral administration by mouth is the most common route of drug administration. Ingestion of a drug go through the digestive process as it travels in the body and is absorbed into the bloodstream the drug eventually reaches the brain and various organs in your body. It takes a while for the drug to exert its effects if taken orally. The advantage of this route is easy and convenient. The disadvantage is some of the drug is destroyed by acids in the stomach. Intravenous injections are administered with a needle into a vein under the skin directly into the blood stream. The drugs are felt immediately as it is quickly

Distribution around the body occurs when the drug reaches the circulation(Neil, 2015), The literature states the route of administration does not have a particular effect on the half life of the drug, however, certain delivery systems like oral sustained release or matrix patch will affect the half life of the drug (Smith, 2008). Half-life is the term used to represent the time taken for the concentration of the drug in the blood to fall down to half of its original value (Neil, 2015). The time to steady dose and interval depends upon the half-life of the drug (Smith, 2008) and the half-life of codeine is 3 hours (Drug bank, 2015). Moreover, in opioids the dose intervals longer than the half-life will cause resurgence of pain, too short intervals

ion. Systemic clearance is defined as the ability of the body to eliminate a drug from body fluid, namely blood or plasma, in volume unit of body fluid per time unit. Systemic clearance describes the whole body elimination of drug including renal and hepatic clearances while organ clearance describes the particular organ clearance. The main specific organs related to systemic clearance are hepatic and renal clearances. Numerous factors influence the systemic clearance rate which includes impairment of hepatic clearance, impairment of renal clearance, altered protein binding concentration, and organ blood flow. The liver plays a major role in system clearance as it contains the major metabolic systems in the body. An impairment of the liver

However, the persistence of drugs in these specimens is not absolutely determined by drug laboratories because of the several contributors that interact and influence the body dynamics and the processes inside. Consequently, drug testing times are affected thus

1. Blood Flow to Tissues: Blood flow is moved at a higher percentage to our main organs so the tissues of the heart, kidneys, and liver would easily be exposed to the drug. There is a lower percentage of blood flow to the skin, bone and other tissues in the body making it harder to get the drug exposure