Dosulepin, a tricyclic antidepressant (TCA) used to treat depression and certain anxiety disorders, was developed in the 1960s and approved for medical use in the late 1960s. Its history is marked by its effectiveness in alleviating depressive symptoms, but also by its risk of cardiac toxicity and overdose, which led to careful monitoring and caution in patients with cardiovascular disease. Dosulepin, a tricyclic antidepressant that inhibits the reuptake of norepinephrine and serotonin, was approved in the United Kingdom in 1967 and has been included in various combination therapy regimens for treatment-resistant depression. Its development featured rigorous clinical trials to determine safety and efficacy, and its use is often guided by careful dose titration to minimize adverse effects.
BRAND NAMES
Prothiaden – the most widely recognized brand for dosulepin, used in the UK and several other countries.
Dothep – another brand available in some regions.
Prothiaden Retard – an extended-release formulation used for sustained antidepressant effect.
MECHANISM OF ACTION
Dosulepin is a tricyclic antidepressant (TCA) that primarily works by inhibiting the reuptake of norepinephrine and serotonin in the central nervous system. By blocking the reuptake transporters, it increases the concentration of these neurotransmitters in the synaptic cleft, enhancing neurotransmission and improving mood.
PHARMACOKINETICS
Absorption
Dosulepin is well absorbed orally, with peak plasma concentrations typically reached 2–4 hours after ingestion. Its bioavailability is moderate, due to first-pass metabolism in the liver.
Distribution
The drug is widely distributed throughout the body, with a volume of distribution (Vd) of approximately 14–21 L/kg, reflecting extensive tissue binding. It is highly protein-bound (90–95%) in plasma.
Metabolism
Dosulepin undergoes extensive hepatic metabolism, primarily via cytochrome P450 enzymes, forming active metabolites such as northiaden, which contribute to its therapeutic effects.
Elimination
The drug and its metabolites are primarily excreted in urine, with a smaller fraction eliminated in feces. The elimination half-life of dosulepin is approximately 8–24 hours, depending on individual metabolism and liver function, allowing for once- or twice-daily dosing.
ADMINISTRATION
Dosulepin is administered orally in tablet or capsule form. The usual starting dose for adults with depression is 75 mg per day, taken either once daily at night or divided into two doses. The dose may be titrated gradually based on clinical response and tolerance, with a typical maintenance range of 75–150 mg per day, and a maximum of 200 mg per day in some cases.
DOSAGE AND STRENGTH
Dosulepin is available in 25 mg, 75 mg, and 150 mg tablets or capsules, with extended-release formulations also available for once-daily dosing. The typical adult starting dose for depression is 75 mg per day, usually taken at bedtime due to its sedative effects. Depending on clinical response and tolerance, the dose may be gradually increased to 150 mg per day, and in some cases up to 200 mg per day under careful medical supervision.
DRUG INTERACTIONS
Dosulepin interacts with several medications due to its effects on the central nervous system and hepatic metabolism via cytochrome P450 enzymes. Concomitant use with other central nervous system depressants (e.g., alcohol, benzodiazepines, opioids, antihistamines) may enhance sedation and drowsiness. Combining dosulepin with MAO inhibitors can lead to hypertensive crises or serotonin syndrome, and it should not be used within 14 days of MAOI therapy.
FOOD INTERACTIONS
Food Interactions: Dosulepin can be taken with or without food, asmeals do not significantly affect its absorption or efficacy. However, patients should avoid alcohol, as it can increase sedation, drowsiness, and the risk of impaired motor coordination when combined with dosulepin.
CONTRAINDICATIONS
Dosulepin is contraindicated in patients with known hypersensitivity to dosulepin, other tricyclic antidepressants, or any component of the formulation. It should not be used in individuals with a recent myocardial infarction, severe heart block, or arrhythmias, due to its potential for cardiotoxicity.
SIDE EFFECTS
Sedation or drowsiness
Dry mouth
Blurred vision
Constipation
Urinary retention
Dizziness or lightheadedness
Weight gain
OVER DOSAGE
Overdose of dosulepin can be serious and potentially life-threatening, primarily due to its effects on the cardiovascular and central nervous systems. Symptoms may include severe drowsiness, confusion, agitation, seizures, hypotension, cardiac arrhythmias, and respiratory depression.
TOXICITY
Dosulepin exhibits high toxicity in overdose, primarily affecting the cardiovascular and central nervous systems. Even moderate overdoses can lead to arrhythmias, hypotension, and respiratory depression, while severe overdoses carry a high risk of fatal outcomes, particularly in children and elderly patients. Neurological effects may include confusion, agitation, seizures, and coma.
