The measurement of doxepin is used to monitor the levels of the drug in the body during treatment. Doxepin belongs to tricyclic antidepressants.
Tricyclic antidepressants are a group of drugs with similar cyclic chemical structures, often used to treat depression on a long-term basis. These drugs, such as amitriptyline (Amitriptyline, Saroten), act by inhibiting the reuptake of norepinephrine and serotonin into the central nervous system and have anticholinergic properties. They are metabolized in the liver, with a variable half-life and a maximum therapeutic level of 4-8 hours after oral administration. As some of the medicines in this group are metabolized to other medicines belonging to the same tricyclic antidepressant group, the levels of all medicines should be measured and taken into account when evaluating clinical symptoms. Monitoring blood drug levels is important, both because the drugs have a narrow therapeutic efficacy window and because they have been shown to be insufficiently correlated with their clinical efficacy. Thus, the occurrence of drug toxicity is a real risk when doses are increased to improve clinical symptoms.
In order to achieve steady-state levels, the drug needs to be taken for 7–21 days.
- Taking certain medications may increase the levels of tricyclic antidepressants: barbiturates, bupropion, cimetidine, corticosteroids, methylphenidate, neuroleptics, oral contraceptives, selective serotonin reuptake inhibitors (SSRIs) (citalopram, fluoxetine, milnacipran, norfluoxetine, paroxetine, sertraline, venlafaxine), valproic acid.
- Taking certain medications can cause levels of tricyclic antidepressants to decrease: barbiturates, chloral hydrate, glutethimide, nicotine (smoking), phenobarbital.
Toxicity from this group of drugs is more readily apparent in the elderly as a result of reduced metabolism as well as due to concomitant use of phenothiazine. Tricyclic antidepressants can cause an increase in serum glucose and a decrease in glucose tolerance. Patients with diabetes should be monitored for the occurrence of hyperglycemia when using these medications. When tricyclic antidepressants are taken concomitantly with the herb Pausinystalia yohimbe, the risk of hypertension is increased.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.