Week 2 Chapter 3 Biopharmaceutics and pharmacokinetics

Question 1

absorption

Answer 1

Medication is absorbed in either liquid or gaseous solution. Therefore, any solid or semisolid drug must first enter into one of these solution forms before becoming absorbed across a cellular membrane. A medication in solid form will generally require more time to enter the body than the same medication in liquid form. Fig. 3-1 depicts the process of solid drug absorption, and Table 3-2 shows the relative rapidity of absorption of various dosage forms. Disintegration and dissolution are generally considered to constitute the beginning of the pharmacokinetic process.

Question 1

active transport

Answer 1

Exceptions to this rule include drugs that use an active transport (carrier transport) system to facilitate movement across membranes (e.g., ferrous ions). An active transport system generally contains a carrier protein to which a drug attaches. The protein complex actively moves the drug across the membrane, then releases it on the postabsorptive side. This is like a piggyback ride, with the protein doing all the work. Active transport can effectively move a drug from an area of low concentration to an area of higher concentration

Question 2

biopharmaceutics

Answer 2

Biopharmaceutics is the area of pharmacology that focuses on the method for achieving effective drug administration. Drugs are placed into vehicles by the manufacturing process. A drug vehicle is a substance into which a drug is compounded for initial delivery into the body. A dosage form—solid, liquid, gas, or any combination of these—is the combination of both the drug and the vehicle used to deliver the drug. A dosage form must be capable of releasing its contents so that the drug can be delivered to the site of action.

Question 3

buccal

Answer 3

Buccal or sublingual tablets, such as nitroglycerin, are designed to disintegrate in the buccal or sublingual space and become absorbed through the buccal or sublingual vasculature.

Question 4

capsule

Answer 4

Capsules generally consist of either a hard or a soft gelatin shell that encloses the active ingredient. A hard gelatin capsule is a two-piece shell made from calcium alginate, methylcellulose, and gelatin. A soft gelatin capsule is a one-piece shell made from similar material. Capsules are designed to mask taste, allow for ease of swallowing, and contribute to a controlled-release mechanism. The capsule must dissolve so that the active ingredient may be released.

Question 5

dissolution

Answer 5

Medication is absorbed in either liquid or gaseous solution. Therefore, any solid or semisolid drug must first enter into one of these solution forms before becoming absorbed across a cellular membrane. A medication in solid form will generally require more time to enter the body than the same medication in liquid form. Fig. 3-1 depicts the process of solid drug absorption, and Table 3-2 shows the relative rapidity of absorption of various dosage forms. Disintegration and dissolution are generally considered to constitute the beginning of the pharmacokinetic process.

Question 5

compressed suppositories

Answer 5

Compressed suppositories or inserts are solid dosage forms generally designed for vaginal or rectal delivery. On contact with the mucosa and in the presence of body temperature, these dosage forms melt away to release the medicinal agent.

Question 6

emulsion

Answer 6

A dosage form consisting of two immiscible* liquids. One liquid appears as globules uniformly dispersed throughout the other liquid. Generally, an emulsifying agent is required to maintain globular stability.

Question 7

dosage form

Answer 7

Medication is absorbed in either liquid or gaseous solution. Therefore, any solid or semisolid drug must first enter into one of these solution forms before becoming absorbed across a cellular membrane. A medication in solid form will generally require more time to enter the body than the same medication in liquid form. Fig. 3-1 depicts the process of solid drug absorption, and Table 3-2 shows the relative rapidity of absorption of various dosage forms. Disintegration and dissolution are generally considered to constitute the beginning of the pharmacokinetic process.

Question 8

passive diffusion

Answer 8

Passive diffusion is the most common means by which drugs traverse cellular membranes. Drugs in solution tend to move from an area of higher concentration to an area of lower concentration. In effect, the concentration of drug at the administration site will influence both rate and extent of absorption

Question 8

pharmacokinetics

Answer 8

For a drug to produce pharmacologic effects in the body, it must first reach the site of action. The process required for a drug to reach the site of action is best described using biopharmaceutic and pharmacokinetic principles. Think of it this way: in order to enjoy your vacation, you have to get there first. Biopharmaceutics and pharmacokinetics are analogous to what you pack, which car you take (sports car or minivan), the gas you buy on the way, and the road you take to get there. If we keep this analogy in mind, some of the “rough spots in the road” will be easier to understand.

Question 8

lipophilicity

Answer 8

The human cell has a double layer of lipid (fat) through which a drug usually must penetrate for absorption to occur. Drugs with good lipid solubility will cross lipid-layered membranes readily. Water-soluble drug forms will not; however, they must have some affinity for (attraction to) water, or they cannot dissolve and be transported by blood and other body fluids. Exceptions to this rule occur when the human cell uses active transport, a small-pore system, or pinocytosis (process by which extracellular fluid is taken into a cell) to allow access across the membrane.

Question 9

inserts

Answer 9

Compressed suppositories or inserts are solid dosage forms generally designed for vaginal or rectal delivery. On contact with the mucosa and in the presence of body temperature, these dosage forms melt away to release the medicinal agent.

Question 10

liquid

Answer 10

Liquid dosage forms include solutions, emulsions, and suspensions (Table 3-1); these are used to administer medication by virtually all routes conceivable.

Question 11

parenteral

Answer 11

Parenteral dosage forms are given by injection under or through one or more layers of skin or mucous membrane. This route includes subcutaneous, intradermal, intrathecal, intracisternal, intramuscular, intravenous, and intraarterial administration. The parenteral route requires that the drug preparation be exceptionally free from all contaminants because the protective skin barrier is being bypassed. The parenteral drug vehicle is usually a solution, a suspension, or an emulsion.

Question 12

solution

Answer 12

A homogenous mixture of solid, liquid, or gas dissolved in another liquid. The solute (drug) is dispersed in the solvent (vehicle).

Question 13

suspension

Answer 13

A solid medication dispersed throughout a liquid medium. A suspending agent is generally added to help maintain uniform dispersion. Suspensions generally require agitation (shaking) before administration.

Question 13

sublingual

Answer 13

Buccal or sublingual tablets, such as nitroglycerin, are designed to disintegrate in the buccal or sublingual space and become absorbed through the buccal or sublingual vasculature.

Question 14

tablet

Answer 14

A tablet generally consists of an active ingredient (drug), various fillers and disintegrators, dyes, flavoring agents, and an outside coating. Fillers help the powdered mass to maintain form when compressed in the manufacturing process. Disintegrators aid in chemical disintegration when subjected to fluids or temperature changes. The disintegration process is required for the solid to become a solution before absorption across a biologic membrane. If something is not done to make it dissolve, the solid will come out in the same lump as initially used. Dyes and flavoring agents help make the dosage form palatable. The coating may help with palatability and aid in the drug-releasing process.

Various types of tablets are produced to aid in the delivery of medication, as follows:

*Compressed tablets are compacted with no special coating; they are subject to chemical degradation from the environment.

*Sugar-coated tablets have a thin layer of sugar coating designed to mask bad taste and to protect the active ingredients from chemical oxidation.

*Film-coated tablets have a thin coating of material other than sugar. This type of coating serves the same function as a sugar coating but is less expensive to manufacture.

*Enteric-coated tablets are designed to pass through the gastric area and release the active ingredients into the small intestine. This technology is used to prevent the strongly acidic contents of the stomach from chemically destroying the activity of a drug. Enteric coating is also used to prevent gastric upset by a drug known to cause significant local irritation in the stomach.

*Multiple-compressed tablets and controlled-release tablets are both designed to mask taste, protect contents against chemical oxidation, and allow for periodic release of contents in a controlled manner throughout the gastrointestinal (GI) transit. Many drugs used for maintenance therapy, such as cardiovascular, pulmonary, antiepileptic, and antirheumatic medications, are formulated this way to allow for once-daily or twice-daily dosing to improve patient compliance.

*Effervescent tablets contain sodium bicarbonate and an organic acid such as citrate or tartrate. These tablets liberate carbon dioxide and disintegrate into an effervescent solution in the presence of water.

*Buccal or sublingual tablets, such as nitroglycerin, are designed to disintegrate in the buccal or sublingual space and become absorbed through the buccal or sublingual vasculature.

Capsules generally consist of either a hard or a soft gelatin shell that encloses the active ingredient. A hard gelatin capsule is a two-piece shell made from calcium alginate, methylcellulose, and gelatin. A soft gelatin capsule is a one-piece shell made from similar material. Capsules are designed to mask taste, allow for ease of swallowing, and contribute to a controlled-release mechanism. The capsule must dissolve so that the active ingredient may be released.

Troches are generally in the form of lozenges or pastilles. These are solids that contain medicine in a hard sugar or glycerinated gelatin base designed to dissolve slowly in the mouth. Topical oral antifungals and anesthetics are most often placed in this dosage form so that continued contact will be made between the medication and the oral mucosa.

Compressed suppositories or inserts are solid dosage forms generally designed for vaginal or rectal delivery. On contact with the mucosa and in the presence of body temperature, these dosage forms melt away to release the medicinal agent.

Liquid dosage forms include solutions, emulsions, and suspensions (Table 3-1); these are used to administer medication by virtually all routes conceivable.

Question 14

troche

Answer 14

Troches are generally in the form of lozenges or pastilles. These are solids that contain medicine in a hard sugar or glycerinated gelatin base designed to dissolve slowly in the mouth. Topical oral antifungals and anesthetics are most often placed in this dosage form so that continued contact will be made between the medication and the oral mucosa