First Pass Metabolism

Enteral Route- The purpose is direct absorption into the bloodstream and directly into the GI Tract. Some advantages are that it is Safe, Administered, and convenient. Some disadvantages are slow onset, No oral nasogastric, or gastrostomy tube.

How does the way a drug enters the body make a difference in its efforts? There are many different routes that drugs can be introduced to the body. One is, sublingual which means that you can dissolvable drugs under the tongue. The blood flows differently, it bypasses

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excretion, the last stage of pharmacokinetics that removes drugs from the system, is via the kidneys."

When arteries bring blood to the nephrons in the kidneys, material dissolved in the plasma is able to be filtered and reabsorbed, making nephrons the functional unit of excretion. The glomerulus is a ball of small blood vessels that filters out salts, urea, amino acids, water, and glucose into the Bowman’s capsule (a collecting

The proximal convoluted tubule is a small tubular structure contained within the nephron of the kidney. It’s involved in the reabsorption of water and solutes from the filtrate located within the nephron. The lining of the proximal convoluted tubule contains numerous protein channels, which use both active and passive transport are used to move substances such as glucose across the tubule's lining and into the interstitial fluid for reabsorption. The epithelium of the proximal convoluted tubule also prevents waste products from being reabsorbed into the bloodstream safeguarding from diseases.

1. Oral and Intravenous are two different ways that a drug may be administered into the body. Oral drugs are absorbed by the intestinal lumen where they are transmitted to the liver to be metabolized, while Intravenous drugs are administered directly into the bloodstream. Because oral medication must go through the liver before being absorbed into the bloodstream, the level of bioavailability, or the amount/extent of the drug absorbed, is less than the medications that are administered directly into the bloodstream. Although intravenous administration allows for quicker absorption, oral medications are easier and more convenient for patients.

Inside the glomerulus will then sift and release and substances or nutrients into Bowman’s capsule. Sodium ions and amino acids can squeeze through the vessels because the vessels have tiny holes in it, which are called Endothelial cell. It is Bowman’s capsules job is to then take any remaining substance that was passed along to the renal tubules. No proteins are able to pass through because the vessels holes in the cell are too small for the proteins to fit through. Also, the more blood there is flowing from the afferent arteriole to the glomerulus, the more leakage there will be in Bowman’s

It retains substances needed by the body, including water, glucose, amino acids, and ions, such as sodium potassium, calcium, chloride, bicarbonate, and phostphate. Reabsorption of Na+ is especially important because more of them pass the glomerular filter than any other substance except water. Sodium ions are reabsorbed in each portion of the renal tubule by several transport systems. Active transport of Na+ promotes reabsorption of water by osmosis. The loss of water from the filtrate creates a concentration gradient for some substances, such as K+, Cl-, HC03-, and urea, that promotes their reabsorption by passive diffusion. The loop of henle reabsorbs about 30% of the filtered K+, 20% filtered Na+, 35% of filtered Cl-, and 15% of the filtered water. Here reabsorption of water by osmosis is not automatically coupled to reabsorption of filtered solutes. Thus, there can only be independent regulation of both your total body water and the osmotic pressure of body fluids. Two hormones, Aldosterone, and Antidiuretic Hormone or ADH, regulate reabsorption in the final portion of the distal convoluted tubule and collecting ducts. About 90% of the reabsorbed water occurs with the reabsorption of solutes such as sodium and glucose, the rest is regulated by ADH. Whereas tubular reabsorption returns substances from the filtrate to the blood, tubular secretion removed materials that are not needed by the body from the blood and adds them to the filtrate. Secreted substances include potassium, hydrogen, and ammonium ions, as well as certain drugs and wastes. Tubular secretion has two principle effects, rids the body of certain materials, and helps to control blood pH by secreting H+ ions and increasing or decreasing HC03-

In the past years, drug delivery via the nasal route has established itself as a competitor and an alternative route over other routes of administration. It provides a higher degree of patient compliance and drugs can be painlessly self-administered by the patient (Illum, 2003). Drugs administered through nasal route are absorbed rapidly and can reach therapeutically effective plasma levels quickly due to highly permeable membranes and rich vasculature of the nasal cavity (Majithiya et al., 2006). In addition, the nasal route offers further advantages over the oral route, especially for those drugs that have poor oral bioavailability due to high hepatic first-pass metabolism, pH instability and enzyme degradation in GIT (Ugwoke et al., 2001).

Pharmacokinetics is term related to the ending of a substance that administered in a living organism. It consists of four phases and these are absorption, distribution, metabolism, and renal elimination, which referred to as ADME. There are two classes for pharmacokinetics: linear pharmacokinetics and non-linear pharmacokinetics. Linear pharmacokinetics of drug is a term refer to dose independent and concentration independent pharmacokinetics, in which pharmacokinetic parameters are constant when the drug concentration change. These parameters are half-life, clearance (CL), and volume of distribution at steady state (Vss). The pharmacokinetic phases like absorption, distribution, and elimination in dose independent pharmacokinetics are followed first order kinetics. In this condition, the changing in the drug dose results directly changing in the drug concentration in a body. In contract, non-linear pharmacokinetics of drug is known dose dependent, time dependent or concentration dependent pharmacokinetics. One or more of the pharmacokinetics parameters

ends up making urine and removing wastes. The kidneys also release and retain water. The

Actions of body on the drug  Non-specific, general processes • Absorption from site of administration • Distribution to the

After instillation, the flow of lacrimal fluid removes instilled compounds from the surface of the eye. Even though the lacrimal turnover rate is only about 1 μl/min the excess volume of the instilled fluid is flown to the nasolacrimal duct rapidly in a couple of minutes. Another source of non-productive drug removal is its systemic absorption instead of ocular absorption. Systemic absorption may take place either directly from the conjunctival sac via local blood capillaries or after the solution flow to the nasal cavity. Anyway, most of small molecular weight drug dose is absorbed into systemic circulation rapidly in few minutes. This contrasts the low ocular bioavailability of less than

Medication or nutrients deposited directly into the vein for the fastest form of absorption (Chrisp & Taylor, 2011)