hP, the component of log P controlling structure-activity relationships amongst non-steroidal anti-inflammatory drugs

Rate and extent of ion-exchange process: the effect of physico-chemical characteristics of salicylate anions

Ten salicylate anions were used as model compounds in order to investigate systematically the impact of compound lipophilicity, valence, aqueous solubility and hydrogen bonding on binding into and release from a strong anion-exchange fiber, Smopex DS-218v. The release of salicylates from the fiber was studied at 1/10, 1/1 or 10/1 molar ratios of the external chloride-ions versus the salicylate bound in the fiber. The Donnan potential between the fiber and external solution (electrostatic interaction) appeared to be the main factor affecting the release of salicylates from the strong base anion-exchange fiber--an increase in the molar amount of the external chloride-ions resulted in a more effective release of all the salicylates from the fiber. The highest chloride-ion concentration (10/1) released the monovalent salicylates practically completely, while the lowest concentration (1/10) released only 10-35% of the loaded salicylates. The nature and strength of salicylate binding to the fiber by non-electrostatic interactions affected also the ion-exchange process, especially in dilute Cl- solutions. Hydrophobic interactions decreased the rate and amount of drug release from the fiber with the most lipophilic salicylates. Hydrogen bonding between the fiber and the compound restricted also the rate and extent of ion-exchange process of the hydrophilic 5-aminosalicylic acid and 5-hydroxysalicylic acid. The amount of divalent 5-carboxylsalicylic acid bound into and released from the fiber was clearly smaller as compared to the monovalent salicylates potentially due to cross-linking of the fiber chains.

Profile and mechanisms of gastrointestinal and other side effects of nonsteroidal anti-inflammatory drugs (NSAIDs)

The popular view that all nonsteroidal anti-inflammatory drugs (NSAIDs) act by inhibiting the production of prostaglandins has been challenged by the discovery that they also affect a wide variety of cellular processes that are important for their therapeutic actions and side effects. Although recognition of the differential activities of new and established NSAIDs on the activities of the cyclooxygenases (COXs) affecting production of inflammatory prostaglandins (from COX-2) and those that are physiologically important (from COX-1) may have significance for the prostaglandin components of the underlying inflammatory and physiologic processes, there are important features of their chemical structures that determine the various cellular and biochemical actions of these agents. Several established NSAIDs have low propensity to cause gastrointestinal (GI) ulceration and bleeding that may relate to these drugs having unique pharmacokinetic characteristics (pro-drugs, protein binding, etc). They also have weak effects on the production of GI mucosal prostaglandins and have specific physicochemical characteristics such that they cause minimal damage to mucosal membranes or effects on nonprostaglandin-related cellular mechanisms important in mucosal defenses. Some of the new COX-2-selective drugs with methyl or amino-sulfonyl moieties have relatively high pKa values and other properties that are similar to established NSAIDs with low GI ulcerogenicity. These physicochemical properties may contribute to the low irritancy of the new COX-2-selective drugs quite apart from their sparing of COX-1 in the GI mucosa. With concerns that some established NSAIDs may accelerate cartilage destruction in osteoarthritis (OA), interest is now focusing on whether the COX-2-selective drugs may have a lower potential for this adverse effect by avoiding the inhibitory effects on cartilage proteoglycan metabolism seen with such drugs as indomethacin and the salicylates. Meloxicam appears to be without inhibitory effects on proteoglycan metabolism, but it remains to be seen if this translates into any beneficial actions on the progression of joint changes in OA observed radiologically or from magnetic resonance imaging.