Trazodone
8-[3-[4-(3-chlorophenyl)piperazin-1-yl]propyl]-6,8,9-triazabicyclo[4.3.0]nona-2,4,9-trien-7-one
Absorption
Well absorbed after administration. Tmax is 1 h on an empty stomach and 2 h with food.
Metabolism
Metabolized to an active metabolite, m-chlorophenyl-piperazine, by CYP3A4.
Elimination
Undergoes biphasic elimination with an initial phase (t½ , 3 to 6 h) followed by a slower phase (t½ , 5 to 9 h).
Alcohol, barbiturates, CNS depressants
CNS depressant effects may be additive.
Carbamazepine
Plasma concentrations of trazodone and its active metabolite may be decreased, producing a decrease in therapeutic effect.
CYP3A4 inhibitors (eg, indinavir, itraconazole, ketoconazole, nefazodone)
May increase trazodone levels, increasing adverse reactions.
Digoxin, hydantoins
Serum levels may be elevated by trazodone, increasing the pharmacologic and adverse reactions.
Hypotensive agents
May cause additive hypotensive effects.
MAOIs
It is unknown whether interactions may take place. Initiate trazodone therapy cautiously if patient is currently taking, or has recently stopped taking, MAOIs.
Phenothiazines, protease inhibitors
Elevated trazodone serum concentrations have occurred, increasing the pharmacologic and toxic effects.
Ritonavir
Increased C max , AUC, and elimination t ½ , and decreased Cl of trazodone.
SSRIs
A serotonin syndrome, including altered consciousness, increased muscle tone, irritability, myoclonus, and shivering may occur.
Warfarin
Reports of increased and decreased PT.
2. 治療1週後症狀可能即會改善，通常在2週內達最大藥效。約25%的病人需治療2～4週。
3. 與CYP3A4抑制藥物如ketoconazole、ritonavir、indinavir等同時投與時，很可能因藥品交互作用造成trazodone的血中濃度升高而引起不良反應。在併用trazodone與具CYP3A4抑制能力的藥物時，須考慮減低trazodone的使用劑量。
4. 在併用carbamazepine時，則可能導致trazodone的血中濃度下降，故在併用時，須密切監控病患是否有增加trazodone使用劑量的需求。
