Neuroregulators and Pain
The major tranquilizers, antipsychotic, or neuroleptic drugs are utilized mainly in the treatment of psychoses. The absorption of these drugs from the gastrointestinal tract is influenced by many factors, including individual variability, dose, presence of food in the stomach, and simultaneous use of antacids. The phenothiazines affect all areas of the central nervous system through their ability to block postsynaptic dopamine receptors interfering with dopamine-mediated neurotransmission. The ability of phenothiazines to serve as effective alpha blockers assumes importance in the treatment of chlorpromazine-induced hypotension. Methotrimeprazine is a phenothiazine derivative specifically marketed as an injectable analgesic for moderate to severe pain. The phenothiazines may induce the hepatic endoplasmic reticulum, affecting metabolism of other drugs detoxified by this system. The neuroleptics, with the exception of methothimeprazine have consistently not been found to be primary analgesics. Promethazine can enhance morphine analgesia, relieve anxiety, and diminish postoperative nausea. It is therefore prescribed with opioids in surgical patients.