Acetylcholine-like molecular arrangement in psychomimetic anticholinergic drugs

Use of the harmonic mean to the determination of dissociation constants of stereoisomeric mixtures of biologically active compounds

Herein we introduce the derivation of a mathematical expression to evaluate the dissociation constant of a mixture of stereoisomers in equal amounts (KdMIX), when the corresponding dissociation constants (Kd) or medium response (MR50) of the pure stereoisomers are known; the final equation takes the form of the harmonic mean. In order to validate the equation, we carried out a bibliographic search of experimental data of enantiomeric molecules with biological activity, considering the Kd's or MR50's of the isolated enantiomers as well as that of the racemate. The comparisons between the experimental dissociation constants of the mixtures (KdEXP or MR50EXP) and the calculated values (KdMIX or MR50MIX) were consistent; the similarity between these values is supported through statistical analyses of group comparison and simple linear correlation. The equation we obtained, which corresponds to the harmonic mean, was used to predict the values of KdMIX (or MR50MIX) or Kd (or MR50) in systems when only two of the experimental values are known: either the dissociation constants of both enantiomers or the Kd (or MR50) of one of the enantiomers and dissociation constant of the racemate.

PCP (phencyclidine): an update

The steady rise in the promiscuous use of phencyclidine (PCP) as a "recreational" drug has recently gained nationwide attention because of the numerous violent and/or bizarre incidents caused by the use of this drug. Because the media often exaggerate reports of bizarre and violent behavior to make a "good" story, the potential PCP user may be tempted to ignore the media warnings. In the case of PCP, however exaggerated the story, a real danger does exist. So, despite numerous newspaper, radio and television warnings about the possible consequences of PCP use and abuse, the incidence of toxic reactions continues to climb. In many cases PCP is sold as other drugs, particularly THC, and in various colored capsules, tablets, liquids and crystals which may explain the increased usage despite the numerous warnings against its use. The advances in laboratory techniques and chemical processess have enabled the clandestine chemist to prepare relatively pure PCP and thus eliminate many of the toxic side effects due to impurities in the drug. In addition, 30 or more psychoactive PCP analogues have been developed and are starting to make an appearance on the street. PCP is perhaps the most potent psychotomimetic compound known at the present time and is capable of inducing a psychosis which is clinically indistinguishable from schizophrenia. The psychosis-producing effects of PCP are the most common toxic effects seen in hospital emergency rooms; but as the amount of PCP taken and/or the simultaneous involvement of other drugs, particularly barbiturates, occurs, severe medical problems (e.g., coma, seizures, respiratory arrest) begin to appear. Death from high doses of PCP or PCP plus other drugs does occur, but the principal cause of death from PCP abuse is due to trauma, homicide or suicide (usually of the bizarre or violent form). Young adult males, persons predisposed to mental illness and naive drug users appear to be the most susceptible to the adverse effects of PCP. The fact that chronic PCP users are starting to increase in number is mute testimony that not all users experience "bad trips" with PCP. Unfortunately for the user, however, this does not guarantee that the next trip will not be a bad one. The effects of chronic use seem to be twofold: severe depression with suicidal thoughts and numerous violent, agitated behavioral patterns. Neither seems to be a suitable alternative. At the present time there is not specific antidote for toxic PCP reactions and the prolonged psychosis induced in some cases does not appear to respond to the standard antipsychotic medications as quickly as do the functional psychoses. The major improvement from a medical standpoint is the development of more sensitive laboratory techniques to confirm the presence of PCP in body fluids. This advance has undoubtedly led to the apparent increase in the number of PCP cases reported by hospitals and to the accuracy of clinical diagnosis by medical, drug or law enforcement communities...