Pharmaceutical Suspensions

During the preparation of physically stable pharmaceutical suspensions, a number of formulation components can be incorporated to maintain the solid particles in the dispersed state. These substances can be classified as (i) components of the suspending system, including wetting agents, dispersants, or deflocculating flocculating agents and (ii) components of the suspending vehicle (external phase), including pH-controlled agents buffers, osmotic agents, coloring flavoring agents,...

Metabolism and Transporters Drug Drug and Drug Nutrient Interactions

Drug molecules may be chemically or metabolically altered at various sites along the GIT, including within gut fluids, within the gut wall, and by microorganisms present in the low end of the tract. These sites are noted in Figure 18. Several examples of enzymatic alteration of certain drugs in gut fluids have been noted previously. Gut fluids contain appreciable quantities of various enzymes, which are needed to accomplish digestion of food. An additional consideration in that regard is that...

Anatomical And Physiological Considerations Of The Gastrointestinal Tract

Villi Diagram Black And White

The GIT is a highly specialized region of the body whose primary functions involve the processes of secretion, digestion, and absorption. Since all nutrients needed by the body, with the exception of oxygen, must first be ingested orally, then processed by the GIT, and then made available for absorption into the bloodstream, the GIT represents a significant barrier and interface with the environment. The primary defense mechanisms employed by the gut to rid it of noxious or irritating materials...

References

Int J Pharm 1991 72 11-18. 2. Cornelissen PJG, Beijersbergen van Henegouwen GMJ, Gerritsma KW. Int J Pharm 1978 1 173-181. 3. Neftel KA, Walti M, Spengler H, et al. Lancet 1982 319 986-988. 4. Connors KA, Amidon GL, Stella VJ. Chemical Stability of Pharmaceuticals A Handbook for Pharmacists. 2nd ed. New York John Wiley & Sons, 1986. 5. Brittain HG, ed. Analytical Profiles of Drug Substances and Excipients. Vol 28. San Diego Academic Press, 2001. 6. Schwartz...

Gastric Emptying

Since increased membrane surface area and decreased thickness of the absorbing membrane favor the small intestine rather than the stomach as the primary site for drug Stomach pH 1-3 Dudodenum pH 5-7 Ileum pH 7-8 Figure 1 Diagrammatic representation of the complexity of the gastro-intestinal tract, with an impression (left) of the size of the GI tract in an adult. The average pH values of the stomach, duodenum, and ileum are shown. The small intestine contains bile salts and other agents, which...

Rcho

Polyunsaturated fatty acids, commonly used in drug formulations, are particularly susceptible to oxidation, and care must be exercised to minimize degradation in formulations containing high concentrations of, for example, vegetable oils (31). The oxidation of phenothiazines to the sulfoxide involves two single-electron transfer reactions involving a radical cation intermediate the sulfoxide is subsequently formed by reaction of the cation with water (32). The ether group in drugs such as...

Hardshell Capsules Advantages

Powder-filled hard-shell capsules often have been assumed to have better bioavailability than tablets. Most likely, this assumption is derived from the fact that the shell rapidly dissolves and ruptures, which affords at least the potential for rapid release of the drug, together with the lack of use of a compaction process comparable to tablet compression in filling the capsules. However, capsules can be just as easily malformulated as tablets. There have been number of reports of...

Parenteral Dosage Forms

Most injectable products are solutions. Solutions of drugs suitable for parenteral administration are referred to as injections. Although usually aqueous, they may be mixtures of water with glycols, alcohol, or other nonaqueous solvents. Many injectable solutions are manufactured by dissolving the drug and any excipients, adjusting the pH, sterile filtering the resultant solution through a 0.22-p.m membrane filter, and, when possible, autoclaving the final product. Most solutions have a...

Effects of Organ Size Blood Flow and Partition Coefficient on Distribution

Organ Blood Distribution

A particular organ in the body may act as a site of distribution or as a site of both distribution and elimination. The relative importance of the various organs as storage or aExcerpted from Oie and Benet, Modern Pharmaceutics, 4th Edition. Figure 1 Process of drug absorption and distribution following administration of a single dose. The drug reaches the desired site of action either directly or via the general circulation. The drug may also reach other tissue sites or may be eliminated by...

Environmental Factors That Affect Reaction Rate

A rational way to develop approaches that will increase the stability of fast-degrading drugs in pharmaceutical dosage forms is by a thorough study of the factors that can affect such stability. In this section, the factors that can affect decomposition rates are discussed it will be seen that, under certain conditions of pH, solvent, presence of additives, and so on, the stability of a drug may be drastically affected. Equations that may allow prediction of these effects on reaction rates are...

Nonvascular Parenteral Routes

For medications that do not require an immediate onset of action or would benefit from sustained, constant blood concentrations without requiring constant infusion, administration can be accomplished using superficial, nonvascular injections. Typically, the sites utilized are the large muscles (intramuscular) or subcutaneous tissue spaces. The muscles, and to a somewhat lesser extent, the subcutaneous tissues are well perfused by the vascular system, thus, both of these sites are frequently...

Info

Abbreviation HSA, Human serum albumin. Abbreviation HSA, Human serum albumin. Irrespective of which salt is added to the solution, the antioxidant moiety depends on the final concentration of the thio compound and the final pH of the formulation (10). While undergoing oxidation reactions, sulfites may be converted to sulfates and other species. Sulfites can also react with certain drug molecules (e.g., epinephrine). Sulfite levels are determined by the reactivity of the drug, the type of...

Peritoneal Dialysis Solutions

The sterile peritoneal dialysis solutions are infused continuously into the abdominal cavity, bathing the peritoneum, and are then continuously withdrawn. The purpose of peritoneal dialysis is to remove toxic substances from the body or to aid and accelerate the excretion function normal to the kidneys. The process is employed to counteract some forms of drug or chemical toxicity as well as to treat acute renal insufficiency. Peritoneal dialysis solutions contain glucose and have an ionic...