HAFIZA MARIA ABAIDPHARMD 4TH YEARROLL NO: P08048

ASSIGNMENT: BIOPHARMACEUTICSPRESENTED TO: Ma’am Madiha

TOPIC:

“PARENTERAL ROUTES OF ADMINISTRATION”

“PARENTERAL ROUTES OF ADMINISTRATION”The word parenteral is derived from the Greek words para, meaning beside, and enteron, meaning intestine, which together indicates something that is done outside the intestine and not by way of the alimentary canal. A drug administered parenterally is the one that is injected through a fine needle into the body at various sites to varying depths.

Drugs destroyed, inactivated or poorly absorbed to produce their effect in the GIT may be parenterally administered. This route is also preferred when rapid absorption is essential.

Factors affecting Parenteral Drug Distribution:Various factors affect the distribution of drugs that have been injected into the general circulation. Few are discussed below.

1.Solubility of the Drug:

Two types of solubility are important:

Solubility in the dosage form vehicle Solubility in the body fluids

Dissolution rates greatly depends upon size of drug particles, pH of the fluids at the injection site, the polymorphic character of drug crystals and a few others.

DisadvantagesDifficult to handle

toxicityStrict sterility requirements

Local inflammation if not administered

properly.

Decrease patient compliance due to pain

and needle phobia.

Advantages

Max bioavailability Quickest onset of action

Given to unconscious/ uncooperative patients

More specific hence used in emergency

conditions.

2.Distribution Coefficient:The determination of the distribution coefficient indicates how much fraction of the drug will be dissolved in the aqueous environment and how much in the lipophillic environment. For instance, a suspension of drug in vegetable oil is likely to be more slowly absorbed than an aqueous solution of the same drug.

3. Area of Absorptive Surface Area of absorptive surface affects oral as well as other routes. Most of the drugs are given orally because of the large area of absorptive surface, so that greater absorption occurs. Intestinal resection decreases the surface area leading to a decreased absorption. Similarly, when the topically acting drugs are applied on a large surface area, they are better absorbed..

4. Vascularity More the vascularity, more is the rate and extent of absorption and vice versa. In shock, blood supply to the GIT is less so the oral route of drug administration is affected. The blood flow to the peripheries is decreased, so absorption in those areas is diminished as well. Therefore, intravenous route is preferred in case of shock.

Vasoconstrictors decrease the blood supply of an area, thus are useful to restrict the local anesthesias so that they remain for a longer duration. Their wash away as well as their toxic effects are decreased in this way.Massage in intramuscular injections improves vascular supply to enhance absorption.

5. pH Acidic pH favors acidic drug absorption while basic pH is better for basic drugs.

6. Presence of other Substances Foods or drugs may interact with the drugs to alter their rate of absorption. Especially for the drugs given orally, food can increase or decrease the absorption.

Antihyperlipidemic drugs like the statins are better absorbed when taken with the food.

7. Other factors:They include particle size, chemical nature, plasma protein binding, concentration of drug and complexation.