In the United States there are nine widely marketed tricyclics and one closely related tetracyclic that are all used to treat depression. The tricyclics can be divided into two main categories: those with tertiary amine groups and those with secondary amine groups. The tertiary amine tricyclics have a greater effect on the reuptake of serotonin, while the secondary amine tricyclics have more influence on the reuptake of norepinephrine. Both groups influence each neurotransmitter.
Imipramine, marketed as Tofranil, has a tertiary amine group and as its tricyclic core is dibenzapine. Closely related to it is Desipramine, marketed as Norpramin, which is its secondary amine equivalent. Of the tricyclics, Desipramine has the lowest incidence of side effects, due to its low affinity for muscarinic, adrenergic and histaminic receptors.
Amitriptyline (Elavil, Endep and Tryptanol) is similar to Imipramine but has a dibenzocycloheptadiene core. It is more potent than Imipramine in terms of muscarinic, adrenergic, histaminic and serotonin effects but has less of an impact on norepinephrine reuptake.
Nortriptyline (Pamelor) is the secondary-amine form of Amitryptiline. Like Amitryptiline, it is more potent than Imipramine in terms of muscarinic, adrenergic and histaminic blockade, and serotonin reuptake, but less effective in blocking norepinephrine reuptake. As the secondary amine counterpart to Amitryptiline, it has the greater impact on norepinephrine reuptake.
Clomipramine (Anafranil) is closely related to Imipramine, but has a chlorine atom appended to its core tricyclic structure. It is more potent than Imipramine at serotonin reuptake inhibition and histamine blockage, but less effective at norepinephrine reuptake inhibition.
Trimipramine (Surmontil) is not as well-researched than the other tricyclics, but there is some evidence that it is less effective than closely-related Imipramine at norepinephrine reuptake inhibition but more effective as an antihistamine. It may or may not have significant effects on the reuptake of dopamine.
Doxepin (Sinequan, Adapin) is a tertiary amine tricyclic that acts very much like imipraminee, but has a structure that more closely resembles that of amitriptyline.
Protriptyline (Vivactil) has a structure similar to Nortriptyline, but with two unsaturated central ring carbons. It is more effective than Nortriptyline at prevention of norepinephrine reuptake, and is also metabolized far more slowly than its saturated counterpart. Its slow metabolism makes it effective at dosages 1/3 the effective dosage of Nortriptyline.
Amoxapine (Asendin) is derived from loxapine, an active neuroleptic, and thus has a structure very different from other Tricyclics. It does, however, prevent norepinephrine reuptake, and is effective at blocking dopamine receptors.
Maprotiline (Ludiomil), is a tetracyclic but has similar action to the tricyclics. It has a greater selectivity as a norepinephrine reuptake inhibitor, but less potency than the rest of the tricyclics.
Imipramine, marketed as Tofranil, has a tertiary amine group and as its tricyclic core is dibenzapine. Closely related to it is Desipramine, marketed as Norpramin, which is its secondary amine equivalent. Of the tricyclics, Desipramine has the lowest incidence of side effects, due to its low affinity for muscarinic, adrenergic and histaminic receptors.
Amitriptyline (Elavil, Endep and Tryptanol) is similar to Imipramine but has a dibenzocycloheptadiene core. It is more potent than Imipramine in terms of muscarinic, adrenergic, histaminic and serotonin effects but has less of an impact on norepinephrine reuptake.
Nortriptyline (Pamelor) is the secondary-amine form of Amitryptiline. Like Amitryptiline, it is more potent than Imipramine in terms of muscarinic, adrenergic and histaminic blockade, and serotonin reuptake, but less effective in blocking norepinephrine reuptake. As the secondary amine counterpart to Amitryptiline, it has the greater impact on norepinephrine reuptake.
Clomipramine (Anafranil) is closely related to Imipramine, but has a chlorine atom appended to its core tricyclic structure. It is more potent than Imipramine at serotonin reuptake inhibition and histamine blockage, but less effective at norepinephrine reuptake inhibition.
Trimipramine (Surmontil) is not as well-researched than the other tricyclics, but there is some evidence that it is less effective than closely-related Imipramine at norepinephrine reuptake inhibition but more effective as an antihistamine. It may or may not have significant effects on the reuptake of dopamine.
Doxepin (Sinequan, Adapin) is a tertiary amine tricyclic that acts very much like imipraminee, but has a structure that more closely resembles that of amitriptyline.
Protriptyline (Vivactil) has a structure similar to Nortriptyline, but with two unsaturated central ring carbons. It is more effective than Nortriptyline at prevention of norepinephrine reuptake, and is also metabolized far more slowly than its saturated counterpart. Its slow metabolism makes it effective at dosages 1/3 the effective dosage of Nortriptyline.
Amoxapine (Asendin) is derived from loxapine, an active neuroleptic, and thus has a structure very different from other Tricyclics. It does, however, prevent norepinephrine reuptake, and is effective at blocking dopamine receptors.
Maprotiline (Ludiomil), is a tetracyclic but has similar action to the tricyclics. It has a greater selectivity as a norepinephrine reuptake inhibitor, but less potency than the rest of the tricyclics.