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 reported to be 10 mg, twice a day, as seen in a study published in the Iranian journal of kidney diseases 3.
- This dose was found to be effective in 87.5% of patients with pruritus resistant to conventional treatment.
- The main adverse effect of doxepin at this dose was drowsiness, which was temporary and easily tolerated by the patients.
Increased Dosage and Efficacy
- There is limited evidence to suggest that increasing the dosage of doxepin enhances its efficacy in treating pruritus.
- A study on the mechanism of action of doxepin in the treatment of chronic urticaria found that doxepin at doses of 50-75 mg/day was effective in treating the condition without significant adverse side effects 4.
- However, a systematic review and meta-analysis of randomized trials on the dose effects of tricyclic antidepressants, including doxepin, found that the evidence for a dose-response relationship is inconclusive 5.
- The review suggested that escalating the dose of doxepin may be justified if side effects are bearable, but the optimal dose for pruritus is not established.
Low-Dose Doxepin
- Low-dose doxepin, typically defined as 1-6 mg, has been investigated for its use in insomnia and has been found to be effective in improving sleep outcomes with minimal effects on sleep architecture 6.
- The use of low-dose doxepin for pruritus has not been extensively studied, but its efficacy and safety profile suggest that it may be a viable option for patients with pruritus who are resistant to conventional treatment.