Phenothiazines were introduced originally to treat psychotic states, including
mania and schizophrenia. Subsequently, many were found to have useful
antiemetic properties and are now used routinely during cancer
chemoradiotherapy. The main mechanism of action of the phenothiazines is
antagonism of D2 receptors, but some of their clinical effects may arise from
blockade of other relevant neurotransmiers.
Prochlorperazine is used routinely in the treatment of PONV and
labyrinthine disorders. It can be administered via intramuscular, oral or
buccal routes. A dverse effects include sedation, hypotension and
extrapyramidal features.
Perphenazine is not licensed for treatment of PONV in the UK but has
proved to be useful as an oral antiemetic preparation.
生物学の機能
Phenothiazines are classified on the basis of their chemistry,
pharmacological actions, and potency. Chemical
classifications include the aliphatic (e.g., chlorpromazine;
Thorazine), piperidine (e.g., thioridazine; Mellaril),
and piperazine subfamilies. The piperazine derivatives
are generally more potent and pharmacologically selective
than the others. The thioxanthenes (e.g., thiothixene;
Navane) are chemically related to the phenothiazines
and have nearly equivalent potency. The butyrophenone haloperidol (Haldol) is structurally distinct
from the two preceding groups, offering greater
potency and fewer autonomic side effects.The dibenzodiazepine
clozapine (Clozaril) bears some structural resemblance
to the phenothiazine group but causes little
extrapyramidal toxicity. The benzisoxazole risperidone
(Risperdal) is representative of many of the newer
agents in having a unique structure relative to the older
groups while retaining antipsychotic potency and a better
side effect profile.
