The Affinity of Antidepressants for Various Receptors

Note 0 = no effect = an equivocal effect + = slight effect -H- = moderate effect +++ = large effect effect. 

Ammonium chloride, an acid-forming salt (4 to 12 g p.o. daily), is indicated in metabolic alkalosis. In addition, as an acidifying agent, it has been used as an expectorant. 

In general, the more lipid soluble a barbiturate derivative is, the greater is its plasma and tissue-binding capacity, the extent of its metabolism, and its storage in adipose tissues. In addition, very lipid-soluble substances have a faster onset of action and a shorter duration of action. 

Barbiturates do not raise the pain threshold and have no analgesic property. In anesthetic doses, they depress aU areas of the CNS, including the hypothalamic thermoregulatory system, respiratory center, and vasomotor centers, as well as the polysynaptic pathways in the spinal column, hi addition, some, such as phenobarbital, but not aU, are anticonvulsants. In toxic doses, barbiturates cause ohguria. They are absorbed orally and distributed widely throughout the body. Barbiturates are metabolized in the fiver by aliphatic oxygenation, aromatic oxygenation, and A-dealkylation. 

The inactive metabolites are excreted in the urine. The administration of bicarbonate enhances the urinary excretion of barbiturates that have a pKa of 7.4 (phenobarbital and thiopental). This generalization is not true of other barbiturates. The long-term administration of barbiturates activates the cytochrome P-450 drug-metabolizing system. 

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