Therapeutically, magnesium salts represent an important class of compounds and exhibit various pharmacologic actions. Examples of magnesium salts are ionic magnesium and magnesium citrate in nephrolithiasis, magnesium salicylate in rheumatoid arthritis, magnesium hydroxide as an antacid as well as a cathartic, and magnesium mandelate as urinary antiseptic. Various anions attached to the cation magnesium, such as oxide, chloride, gluconate, and lactate, affect the delivery of the amounts of elemental magnesium to the target site and thereby produce different pharmacodynamic effects. This review examines the bioavailability and pharmacokinetics of various magnesium salts and correlates pharmacodynamic action with the structure-activity relationship.

Transdermal drug delivery system has been in existence for a long time. In the past, the most commonly applied systems were topically applied creams and ointments for dermatological disorders. The occurrence of systemic side‐effects with some of these formulations is indicative of absorption through the skin. A number of drugs have been applied to the skin for systemic treatment. In a broad sense, the term transdermal delivery system includes all topically administered drug formulations intended to deliver the active ingredient into the general circulation. Transdermal therapeutic systems have been designed to provide controlled continuous delivery of drugs via the skin to the systemic circulation. The relative impermeability of skin is well known, and this is associated with its functions as a dual protective barrier against invasion by micro‐organisms and the prevention of the loss of physiologically essential substances such as water. Elucidation of factors that contribute to this impermeability has made the use of skin as a route for controlled systemic drug delivery possible. Basically, four systems are available that allow for effective absorption of drugs across the skin. The microsealed system is a partition‐controlled delivery system that contains a drug reservoir with a saturated suspension of drug in a water‐miscible solvent homogeneously dispersed in a silicone elastomer matrix. A second system is the matrix‐diffusion controlled system. The third and most widely used system for transdermal drug delivery is the membrane‐permeation controlled system. A fourth system, recently made available, is the gradient‐charged system. Additionally, advanced transdermal carriers include systems such as iontophoretic and sonophoretic systems, thermosetting gels, prodrugs, and liposomes. Many drugs have been formulated in transdermal systems, and others are being examined for the feasibility of their delivery in this manner (e.g., nicotine antihistamines, beta‐blockers, calcium channel blockers, non‐steroidal anti‐inflammatory drugs, contraceptives, anti‐arrhythmic drugs, insulin, antivirals, hormones, alpha‐interferon, and cancer chemotherapeutic agents). Research also continues on various chemical penetration enhancers that may allow delivery of therapeutic substances. For example, penetration enhancers such as Azone may allow delivery of larger‐sized molecules such as proteins and polypeptides.

The chemical structure of phenothiazine provides a most valuable molecular template for the development of agents able to interact with a wide variety of biological processes. Synthetic phenothiazines (with aliphatic, methylpiperazine, piperazine-ethanol, piperazine-ethyl, or piperidine side-chain) and/or phenothiazine-derived agents e.g., thioxanthenes, benzepines, imonostilbenes, tricyclic antidepressants, dimetothiazine, and cyproheptadine have been effective in the treatment of a number of medical conditions with widely different etiology. These include various currently clinically used drugs for their significant antihistamic, antipsychotic, anticholinergic (antiparkinson), antipruritic, and/or antiemetic properties. They are also employed, although to a minor extent, as antidepressants, antispasmodics, analgesics, and antiarrhythemics. Some of these agents are also useful as anti-inflammatory, coronary vasodilator, radioprotective, sedative, antitussive, and skeletal muscle-relaxing medication. Still, others show different degrees of effectiveness as antibacterials, anthelmintics, antimalarials, or local anesthetics; a few are valuable in the control of acute migraine attacks and intractable hiccough. Adding to the seemingly ever-expanding therapeutic use of phenothiazine derivatives, a number of "old" and newly synthesized compounds e.g., "half-mustard-type" and benzo[alpha]phenothiazines, appear to be helpful as multidrug resistance modifiers, a property of particular importance in cancer chemotherapy. Some phenothiazines inhibit human plasmatic leucine-enkephalin aminopeptidase(s), enzymes known to regulate the turnover rate of a wide range of bioactive substances. These findings could lead to the design of new therapeutic treatment modalities for conditions such as Alzeimer's and Creutzfeldt-Jakob disease. Hopefully, this work will help to the rational design of new and improved pharmacological approaches based on a better understanding of the correlation between chemical structure, pharmacodynamic properties, and pharmacological activity of various phenothiazines and phenothiazine-derived classes of drugs.

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This article offers a review of microarray/microneedle technologies and possible future directions in targeting and in the delivery of pharmacologically active compounds for unmet needs in biopharmaceutical research. A better understanding of the production and use of microarrays and microneedles for delivery of peptides, proteins and vaccines is needed.