Modulation of solubility and dissolution of furosemide by preparation of phospholipid complex

Prodrugs, phospholipids and vesicular delivery - An effective triumvirate of pharmacosomes

With the advent from the laboratory bench to patient bedside in last five decades, vesicular systems have now come to be widely accepted as pragmatic means for controlled delivery of drugs. Their success stories include those of liposomes, niosomes and even the lately developed ethosomes and transferosomes. Pharmacosomes, which, as delivery systems offer numerous advantages and have been widely researched, however, remain largely unacknowledged as a successful delivery system. Though a large number of drugs have been derivatized and formulated into self-assembled vesicular systems, the term pharmacosomes has not been widely used while reporting them. Therefore, their relative obscurity may be attributed to the non-usage of the nomenclature of pharmacosomes by the researchers working in the area. We present a review on the scenario that lead to origin of these bio-inspired vesicles composed of self-assembling amphiphilic molecules. Various drugs that have been formulated into pharmacosomes, their characterization techniques, their properties relative to those of other vesicular delivery systems, and the success achieved so far are also discussed.

Drug solubilization by complexation

Drugs must possess some solubility in water to be therapeutically effective after oral or topical administration to the eye, and drugs must be soluble to be formulated as aqueous solutions for, for example, parenteral delivery. A variety of methods can be applied to enhance aqueous solubility of poorly soluble drugs one of which is the usage of solubilizing complexing agents. There are numerous types of complexes and some are more water-soluble than others. Coordination complexes consist of drugs that act as complexing agents (i.e. ligands) and metal ions (i.e. substrates). Examples of coordination complexes are some water-soluble tetracycline-metal ion complexes. Organic molecular complexes can consist of a small substrate (i.e. the drug) and a small (e.g., caffeine) or a large (e.g., polyvinylpyrrolidone) ligand. In inclusion complexes the substrate is partly or completely enveloped by the complexing agent (e.g., cyclodextrin). Finally, pharmacosomes are drug-phospholipid complexes that can not only enhance aqueous solubility of poorly soluble drugs but also their solubility in organic solvents. This is a mini-review of solubilizing complexing agents that are or can be used in pharmaceutical products.