Antipsychotic drugs spectrum

Rats reared in isolation after weaning also experience deficits in PPI (159) and decreased social interaction. This effect has been attributed to enhanced dopaminergic activity (160). Isolation rearing deficits are maximal at puberty (161,162) and thus parallel the ontog-eny of schizophrenia in humans. The disruption of PPI in young rats reared in isolation is reversed by a broad spectrum of antipsychotic drugs including haloperidol, risperidone, clozapine, olanzapine, and quetiapine (153,163). 

Horrobin DF. The effects of antipsychotic drugs on membrane phospholipids a possible novel mechanism of action of clozapine. In Peet M, Glen I, Horrobin DF, eds. Phospholipid Spectrum Disorder in Psychiatry. Marius Press, Carnforth, UK 1999, pp. 113-120. 

Observational studies In a retrospective comparison of risperidone with haloperidol or trifluoperazine in an Asian population with first-episode schizophrenia-spectrum disorders ( = 261), some 90% discontinued treatment before 18 months however, the median time to discontinuation of risperidone was 69 days compared with 27 days for the first-generation antipsychotic drugs [123 ]. Risperidone had a longer time to discontinuation owing to intolerable adverse reactions than haloperidol and trifluoperazine. Nevertheless, lack of comparability precluded firm conclusions. 

Figure 1.15 The Butterfly Angle . Tricyclic drugs consist of anticonvulsants (carbamazepine), antidepressants (amitriptyline), and antipsychotics (chlorpromazine). Although aU three families consist of three interconnected ring systems, the orientation between the rings varies, imparting a different spectrum of bioactivity.

This agent has a broad spectrum of activity encompassing several neurotransmitter systems. In this light, clozapine is similar to such phenothiazines as CPZ and thioridazine (519). It is also subject to a hepatic first-pass effect, which produces metabolites with low or unknown pharmacological activity. It has an elimination half-life ranging from 6 to 33 hours and a volume of distribution (V 5 l /kg) lower than most other antipsychotics. This last quality indicates less drug is sequestered in tissue sites. Plasma levels of the parent compound at or above 350 ng/mL may be associated with a better clinical response ( 66, 520). Plasma levels are lower in men than women, especially male smokers (329). 

However, there are now a number of second-generation (often caiied atypicaiO antipsychotics which have much reduced propensity to induce EPSEs. Most have a narrower spectrum of other receptor effects and a high ratio of 5-HT2 to D2 receptor antagonism. These drugs aii differ from each other in chemicai structure. 

No recognised classification system exists for atypical antipsychotics.Tentative terms based on receptor binding profiles have been applied to certain drug groupings.for example broad spectrum atypicals for clozapine, olanzapine and quetiapine. whilst risperidone and ziprasidone have been described as high affinity serotonin-dopamine antagonists . 

Clinical experience with various pharmacological regimens (mainly mood stabilizers) has suggested that a drug that is efficacious in one manifestation of mania is not necessarily the treatment of choice for the overall spectrum of manic states. Much progress have been made in the treatment of acute manic states, especially since the demonstrated efficacy of the second-generation antipsychotics (e.g. olanzapine, quetiapine, and risperidone) for the treatment of acute mania. However, treatment of acute manic states remains incomplete, and new treatment strategies are in continuous development. ... 

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