Novel antidepressants have also been developed which have combination effects. The agents currently available require strict dietary control to prevent toxic reaction which will elevate blood pressure to lethal levels. MAOIs tend to increase energy but may cause insomnia, even at low dosages. No dietary restrictions are necessary with TCAs. They act to increase two neurotransmitters serotonin and norepinephrine.
Onset of action is generally two to four weeks after treatment is started.
This allows the development of certain blood concentrations and then for the agent to cross into the neuron. Periodic assessment of blood level is useful to assure an effective concentration. Side effects with TCAs are largely caused by their antihistaminic and anticholinergic properties. They tend to be more sedating and commonly induce initial sleep improvement. They also tend to cause dry mouth, delayed urination, sexual dysfunction, constipation, and lightheadedness.