Alkaloids selective serotonin

Harmala alkaloids are potent inhibitors of monoamine oxidase (Callaway and Grob 1998). Thus, if combined with other antidepressants, such as selective serotonin reuptake inhibitors, there is potential for serious side effects. Harmaline or its metabolites also cross the placental barrier (Okonmah et al. 1988). 

An opioid analgesic should be given only if ergot alkaloids or selective serotonin receptor agonist medications (migraine-specific medications) are not effective in treating the pain. 

A Figure 7.2 Basic drugs and classes, the largest subgroup in the acid-base classification scheme. The alkaloids are (or at least once were) derived from plant matter, while nonalkaloids are generally synthetic or semisynthetic. Tropane alkaloids Include cocaine, while tryptamines include mescaline and psilocyn. Caffeine and theophylline are xanthine alkaloids. The selective serotonin reuptake inhibitors (SSRIs) include the second-generation SSRI antidepressants. Prozac (fluoxetine, shown) and Paxil belong to this class. 

Two general classes of alkaloids are distinguished in ergot amine alkaloids and amino acid alkaloids (table 5.9) (Peroutka 1996). While the amine alkaloids are selective for antagonist effects on serotonin receptors, the amino acid alkaloids are less selective and act upon other monoamine receptors. The constituents of interest for cognitive enhancement are predominantly the amine alkaloids. 

Phenoxybenzamine binds covalently to a receptors, causing irreversible blockade of long duration (14-48 hours or longer). It is somewhat selective for 1 receptors but less so than prazosin (Table 10-1). The drug also inhibits reuptake of released norepinephrine by presynaptic adrenergic nerve terminals. Phenoxybenzamine blocks histamine (Hi), acetylcholine, and serotonin receptors as well as receptors (see Chapter 16 Histamine, Serotonin, the Ergot Alkaloids). 

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