From the Guidelines
Oral doxepin is effective in treating pruritus at a dose of 10-50 mg per day. The recommended starting dose is 10 mg taken 1-3 times daily, with a maximum dose of 50 mg per day 1. Higher doses of doxepin, above 30 mg per day, may not provide additional efficacy in relieving itch, but rather increase the risk of adverse effects such as drowsiness, dry mouth, and constipation.
Key Points
- Doxepin has high histamine H1 receptor antagonist activity and sedative effects, which may help reduce pruritus 1.
- The sedating effects of doxepin have not been clearly separated from the antipruritic effects 1.
- Children can develop tolerance to sedating properties of antihistamines, despite the persistence of antimuscarinic and anticholinergic side effects 1.
- Doxepin may be used at an initial dose of 10 mg nightly, which can be titrated to reach the desired effect 1.
Dosage Considerations
- The maximum dose of doxepin is 50 mg per day.
- Higher doses of doxepin may increase the risk of adverse effects, rather than providing additional efficacy in relieving itch.
- The dose of doxepin should be individualized based on the patient's response and tolerance to the medication.
From the FDA Drug Label
For most patients with illness of mild to moderate severity, a starting daily dose of 75 mg is recommended Dosage may subsequently be increased or decreased at appropriate intervals and according to individual response. The usual optimum dose range is 75 mg/day to 150 mg/day. In more severely ill patients higher doses may be required with subsequent gradual increase to 300 mg/day if necessary. Additional therapeutic effect is rarely to be obtained by exceeding a dose of 300 mg/day
The effective dose of oral doxepin for pruritus is not explicitly stated in the label, but the recommended dosage range for most patients is 75 mg/day to 150 mg/day.
- Increased dosage may enhance efficacy in some patients, but additional therapeutic effect is rarely obtained by exceeding a dose of 300 mg/day 2.
From the Research
Effective Dose of Oral Doxepin for Pruritus
- The effective dose of oral doxepin for pruritus is 10 mg, twice a day, as reported in a study published in the Iranian journal of kidney diseases 3.
- This dose was found to be effective in improving pruritus in 87.5% of patients with end-stage renal disease who underwent hemodialysis.
Increased Dosage and Efficacy
- There is limited evidence on the effect of increased dosage of doxepin on pruritus, as most studies have focused on its use in depression and insomnia.
- A study on the dose effects of tricyclic antidepressants in the treatment of acute depression found that increasing the dose of doxepin may not necessarily enhance efficacy, but may increase the risk of adverse events 4.
- However, this study did not specifically investigate the use of doxepin for pruritus, and more research is needed to determine the optimal dose for this indication.
Safety and Tolerability
- Doxepin has been found to be generally well-tolerated at low doses, with common adverse events including drowsiness, dry mouth, and dizziness 3, 5, 6.
- Higher doses of doxepin may be associated with increased risk of adverse events, including cardiovascular effects such as prolonged QTc interval and increased heart rate 7.