Conventional forms of drug administration generally rely on pills, eye drops, ointments, and intravenous solutions. Recently, a number of novel drug delivery approaches have been developed. These approaches include drug modification by chemical means, drug entrapment in small vesicles that are injected into the bloodstream, and drug entrapment within pumps or polymeric materials that are placed in desired bodily compartments (for example, the eye or beneath the skin). These techniques have already led to delivery systems that improve human health, and continued research may revolutionize the way many drugs are delivered.

http://science.sciencemag.org/content/sci/249/4976/1527.full.pdf

New methods of drug delivery.

Biodegradation and biocompatibility of PLA and PLGA microspheres

Years of cumulative research can result in the development of a clinically useful drug, providing either a cure for a particular disease or symptomatic relief from a physiological disorder. A lead compound with a desired pharmacological activity may have associated with it undesirable side effects, characteristics that limit its bioavailability, or structural features which adversely influence its metabolism and excretion from the body. Bioisosterism represents one approach used by the medicinal chemist for the rational modification of lead compounds into safer and more clinically effective agents. The concept of bioisosterism is often considered to be qualitative and intuitive.1 The prevalence of the use of bioisosteric replacements in drug design need not be emphasized. This topic has been reviewed in previous years.2-5 The objective of this review is to provide an overview of bioisosteres that incorporates sufficient detail to enable the reader to understand the concepts being delineated. While a few popular examples of the successful use of bioisosteres have been included, the George Patani graduated with a B.Pharm. in 1992 from the College of Pharmaceutical Sciences, Mangalore University at Manipal, India. In 1996, he received his M.S. in Pharmaceutical Science at Rutgers University under the direction of Professor Edmond J. LaVoie. He is presently pursuing graduate studies in pharmaceutics. His current research interests are focused on drug design and controlled drug delivery.

https://www.mch.estranky.sk/file/228/1996chemrev96-3147-76_bioisosterism.pdf

Bioisosterism: A Rational Approach in Drug Design.

The manufacturing techniques of various drug loaded biodegradable poly(lactide-co-glycolide) (PLGA) devices.

This review covers recent developments in the area of particle engineering via spray drying. The last decade has seen a shift from empirical formulation efforts to an engineering approach based on a better understanding of particle formation in the spray drying process. Microparticles with nanoscale substructures can now be designed and their functionality has contributed significantly to stability and efficacy of the particulate dosage form. The review provides concepts and a theoretical framework for particle design calculations. It reviews experimental research into parameters that influence particle formation. A classification based on dimensionless numbers is presented that can be used to estimate how excipient properties in combination with process parameters influence the morphology of the engineered particles. A wide range of pharmaceutical application examples—low density particles, composite particles, microencapsulation, and glass stabilization—is discussed, with specific emphasis on the underlying particle formation mechanisms and design concepts.

/pdf/pharmaceutical-particle-engineering-via-spray-drying-1wv9pxpwlb.pdf

Pharmaceutical particle engineering via spray drying.

The pharmacokinetic parameters of leuprolide acetate, a potent analogue of LH-RH, were determined in rats and dogs after i.v. and s.c. dosing with leuprolide solution. The effective human dose of once-a-month injectable microspheres of leuprolide was estimated to be about 3.2 to 8.1 mg analogue/month using these parameters. After microsphere injection at three different doses in rat serum leuprolide concentrations were sustained for over 4 weeks, and the AUCs and mean serum levels were linearly correlated with the dose. The serum levels and urinary excretion of the analogue in rats after repeated s.c. injection of the microspheres every 4 weeks exhibited similar profiles after each injection; no changes of the absorption and excretion of the analogue after the repeated injection could be demonstrated. The serum levels of the analogue metabolite (M-I) were 21% of the intact form 3 hr after injection of the microspheres but very low at the steady state after 1 to 4 weeks.

Pharmacokinetics of once-a-month injectable microspheres of leuprolide acetate.

Sustained release microcapsules including a water soluble drug and an organic basic substance as a drug retaining substance of this invention not only have a high rate of incorporation (trapping rate), but also show little initial release so that they can be administered safely and bring about persistent, stable sustained release.

Sustained release microcapsule for water soluble drug

When sustained-release adhesive and non-adhesive microspheres which release the same drugs at similar rates are administered orally, drug absorption after administration of adhesive microspheres should, if the gastrointestinal residence of adhesive microspheres is prolonged as a result of mucoadhesion, be higher than that after administration of non-adhesive microspheres. The gastrointestinal transit of oral adhesive microspheres in man has been evaluated pharmacokinetically using furosemide and riboflavin, compounds with limited absorption sites in the upper small intestine. In a preliminary experiment with fasted rats it was confirmed that a higher percentage of the drug remained in the stomach and that plasma drug levels were higher when furosemide was administered in the form of adhesive rather than non-adhesive microspheres. Two kinds of sustained-release microsphere, adhesive and non-adhesive, containing furosemide and riboflavin in hard gelatin capsules were prepared and orally administered to 10 healthy fasted volunteers in a cross-over design. Areas under the plasma concentration-time curves (AUC) were 1.8 times larger for furosemide and urinary recovery was 2.4 times higher for riboflavin when adhesive microspheres rather than when non-adhesive microspheres were used. When adhesive microspheres containing riboflavin were administered to fed volunteers, urinary recovery was 2.1 times higher and mean residence time (MRT) was more prolonged than when the microspheres were administered to fasted volunteers. Adhesive microspheres were found to adhere to the gastric or intestinal mucosa with high affinity in man and rats, resulting in prolonged gastrointestinal residence.

Evaluation of Oral Mucoadhesive Microspheres in Man on the Basis of the Pharmacokinetics of Furosemide and Riboflavin, Compounds with Limited Gastrointestinal Absorption Sites

A copolymer of lactic acid and glycolic acid which has a weight-average molecular weight of not less than about 5000 and a dispersity of about 15 to 2 is advantageously used as a biodegradable polymer for medical preparation

Copolymer and method for producing the same

PROLONGED RELEASE PREPARATION AND POLYMERS THEREOF Abstract of the Disclosure 1. A polymer for a prolonged release preparation which comprises (A) a polylactic acid and (B) a copolymer of glycolic acid and a hydroxycarboxylic acid of general formula wherein R stands for an alkyl group having 2 to 8 carbons, at a weight ratio of (A) and (B) in the range of 10/90 to 90/10. The drug is released at a constant rate from the preparation over the total release period without a large burst at the initial stage. Furthermore, the drug release period of the preparation can be freely controlled by varying the blending ratio of (A) and (B).

Yasuaki Ogawa

Papers

Pharmacokinetics of once-a-month injectable microspheres of leuprolide acetate.

Sustained release microcapsule for water soluble drug

Evaluation of Oral Mucoadhesive Microspheres in Man on the Basis of the Pharmacokinetics of Furosemide and Riboflavin, Compounds with Limited Gastrointestinal Absorption Sites

Copolymer and method for producing the same

Prolonged release preparation and polymers thereof