Silenor is a brand name of the medication doxepin. Doxepin is a tricyclic antidepressant. In addition to being prescribed for major depressive disorder, doxepin is also commonly prescribed for the treatment of insomnia, manic-depressive conditions and anxiety, especially when anxiety occurs alongside alcoholism.
The metabolism of Silenor can vary greatly depending on the patient’s genetic variations of certain enzymes. As a rule, tricyclics like doxepin can continue to linger in the blood plasma for up to two weeks. Because of this, it’s advised that patients wait at least 14 days before beginning other medications that may be contraindicated for use with doxepin. These include monoamine oxidase inhibitors (MAOIs). MAOIs can trigger a dangerous serotonin overload when combined with even residual amounts of Silenor.
Doxepin achieves its effects by acting on a variety of neurotransmitters in the brain, primarily serotonin and norepinephrine. These monoamine neurotransmitters have been closely linked to both anxiety and depression and have implications for sleep disorders as well. At low doses, Silenor can be an effective antihistamine and is even used as a topical ointment for allergic reactions expressed through the skin.
Silenor is available with a prescription from a qualified physician or psychiatrist. The risk of developing a dependence on doxepin is low. Treatment with doxepin is highly dose-dependent and should only be taken under close doctor supervision. At low doses, such as for the treatment of mild insomnia, withdrawal effects can be non-existent and rebound insomnia negligible. Doxepin consistently maintains effectiveness without the development of tolerance for an average of three months in most patients.
According to the federal government, tricyclic antidepressants like doxepin are considered to be non-addictive. However, on rare occasions, patients with a pre-existing history of substance misuse have experienced addiction-like behavior in response to consistently high doses. These occurrences have been documented with the use of the tricyclics tianeptine and amineptine.
Doxepin’s wide variety of applications can be attributed to its versatile bonding profile, which varies according to dose. At daily doses between 25 to 300 mg a day, Silenor can be an effective treatment for depression. The average daily dose of doxepin for the treatment of depression is 75 mg a day. For the treatment of insomnia, daily doses can range between 25 to 50 mg, although in severe cases doses of up to 150 mg may be prescribed. For use as an antihistamine to treat allergic reactions, dermatological treatments range between three to 25 mg. At such low doses, doxepin’s side effects become negligible for most patients. At doses above 25 mg, doxepin has significant effects on serotonergic (serotonin), cholinergic (acetylcholine) and adrenergic (adrenaline) pathways.
The half-life of Silenor ranges between 15 to 18 hours from the time of ingestion. About ten percent of Caucasian patients have significant difficulty metabolizing doxepin. This can lead to plasma concentrations at levels eight times above normal. Doxepin is metabolized via oxidation with N-demethylation in the liver.
The metabolism of Silenor is highly stereoselective and is primarily metabolized by three different enzymes. Genetic variations of these enzymes are expressed in select patients. These enzymatic variations can result in differences in the way Silenor is metabolized by the body. Individuals with specific variations of the enzyme CYP2D6, for example, may have increased concentrations of doxepin and, therefore, experience worse side effects. These can include adverse effects on the nervous system affected by the drug’s anticholinergic effects. Most individuals, however, have a normal metabolism of doxepin. These individuals are referred to as “extensive metabolizers.” Other categories of metabolizers include poor, intermediate and ultra-rapid metabolizers. Poor metabolizers break down Silenor too slowly, while ultra-rapid metabolizers do so too fast. Ultra-rapid metabolizers have an increased risk pharmacological failure.
The testable range for doxepin can vary dramatically from person-to-person due to the drug’s high metabolic variability as determined by genetic variations of certain enzymes. Peak plasma levels of Silenor are reached roughly three hours after ingestion when taken without food and six hours after ingestion when taken with a substantial meal. On average, tricyclic antidepressants like Silenor can be present in the urine as early as eight hours following ingestion. With doxepin, testable levels in the urine can be present within 15 hours of taking the drug. Upon cessation of treatment, testable levels may linger in the urine for up to seven days on average.
Silenor Side Effects
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