Although metrifonate has been extensively tested in phase 3 trials, a New Drug Application (NDA) to the FDA was disapproved because of concerns about muscle weakness and respiratory depression

occurring in a small proportion of patients treated with the higher efficacious doses. This circumstance has raised concern that other ChEIs may also have particular neurotoxicity or may have more serious chronic effects in some patients than the typical acute, and usually mild, gastrointestinal cholinergic effects described in clinical trials. Rivastigmine Rivastigmine (ExelonTM) is a pscudoirrcversible, selective Inhibitors,research,lifescience,medical AChE ABT-199 research buy subtype inhibitor. Although it, inhibits both AChE and BChE, it. is relatively selective to AChE in the CNS, and within the CNS, to areas of the cortex and hippocampus, and to the Gl monomcric form of AChE. Moreover, rivastigmine is not metabolized by the hepatic microsome system. Rather, after binding to AChE, the carbamate portion of rivastigmine is slowly hydrolyzed, cleaved, conjugated to a Inhibitors,research,lifescience,medical sulfate, and excreted. Thus, it, is unlikely to have significant pharmacokinetic interactions with other medications. Following early phase 2 proof-of-concept trials (eg, ref 24; see Table I). Four phase 3 clinical trials were completed, all of similar design, and differing mainly in dosing methods. The results of two have

been published.25,26 Some results of the third Inhibitors,research,lifescience,medical have been included in secondary reports.27-29 A fourth trial, allowing an adjustable dosage, remains unpublished. Table I. Description of key phase 3 and 4 cholinesterase inhibitor placebo-controlled, randomized clinical trials. All trials included only patients with probable Alzheimer’s disease (NINCDS-ÀDRDÀ Inhibitors,research,lifescience,medical criteria) or Dementia of Alzheimer’s type (DSM-IV … Table II. Summary Inhibitors,research,lifescience,medical of safety data in key phase 3 and 4 cholinesterase inhibitor placebo-controlled, randomized clinical trials. All trials included only patients with probable Alzheimer’s disease (NINCDS-ADRDA criteria) or Dementia of Alzheimer’s type (DSM-IV criteria), … Rivastigmine was approved by a centralized

procedure in Europe including all 15 member states of the EU in May 1998, as well as by the FDA in April 2000. The Tryptophan synthase new prescribing information document incorporates the most recent labeling revisions. US prescribing information can be found at the FDA’s web site (http://fda.cder.gov), and at Novartis* web site (htip:/www.novartis.com). Galantamine Galantamine (formerly galanthamine), an alkaloid extracted from Amaryllidaceae (Galanthus woronowi, the Caucasian snowdrop), but which is now synthesized, is a reversible, competitive inhibitor of AChE with relatively less BChE activity.30,34 Since competitive inhibitors compete with ACh at AChE binding sites, their inhibition is, theoretically, dependent on the intrasynaptic ACh concentration in that they will be less likely to bind to sites in brain areas that have high ACh levels.