Trazodone

Absorption

Trazodone is rapidly absorbed in the gastrointestinal tract after oral administration, with a bioavailability ranging from 63-91% and an AUC0?t of 18193.0 ng·h/mL. Food may impact absorption in a variable fashion, and may sometimes lead to decreases in the Cmax of trazodone. In the fed state in 8 healthy volunteers, the Cmax was measured to be 1.47 +/- 0.16 micrograms/mL, and in the fasted state, was measured at 1.88 +/- 0.42 micrograms/mL. The average Tmax after a single dose of 300 mg was 8 hours. Food may increase absorption by up to 20%.

Toxicity

The oral LD50 of trazodone is 690 mg/kg in rats.
An overdose of trazodone may result in central nervous system, cardiac, respiratory effects. Signs and symptoms may include dyspnea, bradycardia, hypotension, mental status changes, lack of coordination, and coma, among others. In addition, an overdose may result in priapism, a persistent unrelievable penile tissue erection that may cause permanent damage if not treated promptly. No specific antidote exists for a trazodone overdose. If an overdose occurs, consider the possibility that trazodone may have been combined with other drugs. Contact a poison control center in case of overdose for the most current management guidelines. Dialysis does not accelerate trazodone clearance.

Chemical properties

Brown Oil

Originator

Trittico,Angelini,Italy,1972

The Uses of Trazodone

It is believed that trazodone, in therapeutic doses, inhibits the neuronal reuptake of serotonin. It is not a MAO inhibitor or a CNS stimulator. It has a minor influence on the reuptake of norepinephrine and dopamine. In addition, it does not bind with cholinergic or α-adrenergic receptors.

The Uses of Trazodone

Antidepressant

Indications

Trazodone is indicated for the treatment of major depressive disorder (MDD). It has been used off-label for adjunct therapy in alcohol dependence, and off-label to treat anxiety and insomnia. It may also be used off-label to treat symptoms of dementia, Alzheimer’s disease, schizophrenia, eating disorders, and fibromyalgia due to its effects on various neurotransmitter receptors.

Background

Trazodone is triazolopyridine derivative from the serotonin receptor antagonists and reuptake inhibitors (SARIs) class of antidepressants. It is used in adults and has been shown to be comparable in efficacy to other drugs such as tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and serotonin-norepinephrine receptor inhibitor (SNRIs) in the treatment of depression. A unique feature of this drug is that it does not promote the anxiety symptoms, sexual symptoms, or insomnia, which are commonly associated with SSRI and SNRI therapy. Trazodone acts on various receptors, including certain histamine, serotonin, and adrenergic receptors, distinguishing it from other antidepressants that cover a narrow range of neurotransmitters. It was initially granted FDA approval in 1981.

Definition

ChEBI: An N-arylpiperazine in which one nitrogen is substituted by a 3-chlorophenyl group, while the other is substituted by a 3-(3-oxo[1,2,4]triazolo[4,3-a]pyridin-2(3H)-yl)propyl group.

Indications

Trazodone (Apothecon) is also classified as an antidepressant agent. It is a selective serotonin reuptake inhibitor (SSRI), partial agonist at postsynaptic 5-HT1A receptors, and exhibits α-adrenoceptor blocking actions.
Trazodone may cause priapism and enhance libido, and it prolongs nocturnal erections. This drug has been used both orally and by intracavernosal injection. It can be used alone or in combination with yohimbine. Overall, trazodone has not been as effective in treating ED as other available agents. However, it may be an option for selected patients, particularly those with performance anxiety or low libido.

Manufacturing Process

In an initial step, 2-chloropyridine is reacted with semicarbazide to give s_x0002_triazolo-[4,3-a]-pyridine-3-one. To a boiling solution of 6.7 grams s-triazolo-[4,3-a]-pyridine-3-one in 80 ml dioxane, there is added 2.4 grams 50% NaH. The mixture is refluxed during 1 hour under stirring, then 13.5 grams 1-(3-chloropropyl)-4-mchlorophenylpiperazine is added. The mixture is refluxed under stirring for 20 hours, cooled, diluted with an equal volume of ether, the sodium chloride filtered out, and ethereal HCl added. The solid which precipitates is filtered out and crystallized from 95% alcohol. Yield is 13.5 grams, MP 223°C. The following is an alternative method of preparation: 1 gram 2-(γ- chloropropyl)-s-triazolo-[4,3-a]-pyridine-3-one and 5 ml saturated ammonia alcoholic solution are heated for 5 hours in a closed tube at 100°C. The contents of the tube are cooled, the ammonium chloride filtered out and the solvent is removed. There remains a residue of 0.9 grams 2-(γ-aminopropyl)- s-triazolo-[4,3-a]-pyridine-3-one.
This residue is dissolved in isopropyl alcohol and 1 gram N-bis-chloroethylaniline is added to it. The mixture is refluxed for 3 hours. The solvent is removed at a reduced pressure, the residue is treated with 50% potassium carbonate, and extracted with ether. By treating with ethereal hydrochloric acid, 2-N'-m-chlorophenylpiperazino-propyl-s-triazole[4,3-a]pyridine-3-one hydrochloride is precipitated; MP 223°C.

brand name

Beneficat;Bimaran;Deprax;Devidone;Manegan;Molipaxin;Pragmarel;Pragmazone;Taxagon;Thittico;Thombran;Thromban;Tombran;Tramensan;Tritico;Trittico.

Therapeutic Function

Tranquilizer

World Health Organization (WHO)

Trazodone, an antidepressant indicated for the treatment of a wide range of depressive illness, was introduced in 1973. Although it is registered for use in many countries with highly evolved regulatory authorities, approval for registration was not granted in Norway because of a suspicion of carcinogenicity in a two-year rat study.

Biological Functions

Trazodone (Desyrel) was introduced in the early 1980s as a second-generation antidepressant. It blocks the neuronal reuptake of serotonin and is an antagonist at the 5HT2-receptor. Also, its major metabolite, mchlorophenylpiperazine (mCPP), is a postsynaptic serotonin receptor agonist. When compared to the TCAs, trazodone is relatively free of antimuscarinic side effects, but it does block the α-adrenoceptor. Common side effects include marked sedation, dizziness, orthostatic hypotension, and nausea. Priapism is an uncommon but serious side effect requiring surgical intervention in one-third of the cases reported. Because of trazodone’s sedating quality, it is often used in low doses to counter the insomnia associated with the newer antidepressants, such as the SSRIs.

Mechanism of action

Trazodone acts as an antagonist at 5-HT2A receptors and is a weak inhibitor of 5-HT reuptake at the presynaptic neuronal membrane, potentiating the synaptic effects of 5-HT. Its mechanism of action is complicated by the presence of its metabolite, m-chlorophenylpiperazine, which is a 5-HT2C agonist. At therapeutic dosages, trazodone does not appear to influence the reuptake of dopamine or NE within the CNS. It has little anticholinergic activity and is relatively devoid of toxic cardiovascular effects. The increase in serotonergic activity with long-term administration of trazodone decreases the number of postsynaptic serotonergic (i.e., 5-HT2) and β-adrenergic binding sites in the brains of animals, decreasing the sensitivity of adenylate (or adenylyl) cyclase to stimulation by β-adrenergic agonists. It has been suggested that postsynaptic serotonergic receptor modification is mainly responsible for the antidepressant action observed during long-term administration of trazodone. Trazodone does not inhibit MAO and, unlike amphetamine-like drugs, does not stimulate the CNS.
Trazodone is rapidly and almost completely absorbed from the GItract following oral administration, with an oral bioavailability of approximately 65%. Peak plasma concentrations of trazodone occur approximately 1 hour after oral administration when taken on an empty stomach or 2 hours when taken with food. At steady state, its plasma concentrations exhibit wide interpatient variation.
Trazodone is extensively metabolized in the liver by N-dealkylation to its primary active metabolite, m-chlorophenylpiperazine (m-CPP), which subsequently undergoes aromatic hydroxylation to p-hydroxy-m-CPP. In vitro studies indicate that CYP3A4 is the major isoform involved in the production of m-CPP from trazodone (and CYP2D6 to a lesser extent). The p-hydroxy-m-CPP and oxotriazolopyridine-propionic acid (the major metabolite excreted in urine) are conjugated with glucuronic acid. Less than 1% of a dose is excreted unmetabolized.

Pharmacokinetics

Trazodone treats depressed mood and other depression-related symptoms and shows benefit in the treatment of insomnia due to its sedating effects. It is known to prolong the cardiac QT-interval. Memory, alertness, and cognition may be decreased by trazodone, especially in elderly patients due to its central nervous system depressant effects.
A note on priapism
Trazodone has been associated with the occurrence of priapism, a painful and persistent incidence of penile tissue erection that is unrelievable and can cause permanent neurological damage if left untreated. Patients must be advised to seek immediate medical attention if priapism is suspected.

Clinical Use

Trazodone is a phenylpiperazine–triazolopyridine antidepressant that is structurally unrelated to most of the other antidepressant classes.Trazodone is used primarily in the treatment of insomnia, mental depression, or depression/anxiety disorders. The drug also has shown some efficacy in the treatment of benzodiazepine or alcohol dependence, diabetic neuropathy, and panic disorders.

Synthesis

Trazodone, 2-[3-[4-(m-chlorophenyl)-1-piperazineyl]propyl]-s-triazolo[4,3-a] piridine-3(2H)-one (7.3.8), is synthesized from 2-chloropiridine, the reaction of which with semicarbazide gives s-triazolo-3-one[4,3-a]pyridine (7.3.7). Alkylation of this product using 1-(3-chloropropyl)-4-(3-chlorophenyl)piperazine gives trazodone (7.3.8) [61,62].

Drug interactions

Trazodone possesses serotonergic activity; therefore, the possibility of developing 5-HT syndrome should be considered in patients who are receiving trazodone and other SSRIs or serotonergic drugs concurrently. When trazodone is used concurrently with drugs metabolized by CYP3A4, caution should be used to avoid excessive sedation. Trazodone can cause hypotension, including orthostatic hypotension and syncope; concomitant administration of antihypertensive therapy may require a reduction in dosage of the antihypertensive agent.

Metabolism

Trazodone is heavily metabolized and activated in the liver by CYP3A4 enzyme to the active metabolite, m-chlorophenylpiperazine (mCPP). The full metabolism of trazodone has not been well characterized. Some other metabolites that have been identified are a dihydrodiol metabolite and carboxylic acid.