# Rapid intravenous symptom-inhibiting fentanyl induction (SIFI) to optimize rotation onto oral opioid agonist therapy among individuals who use unregulated fentanyl: protocol for an open-label, single arm clinical trial

## TL;DR

This study proposes a new method to quickly start opioid treatment for people using unregulated fentanyl, aiming to reduce withdrawal and improve treatment success.

## Contribution

This is the first outpatient study to rapidly estimate opioid tolerance and use it to calculate individualized starting doses of oral opioid therapy.

## Key findings

- The SIFI protocol aims to safely estimate opioid tolerance and determine individualized starting doses of methadone or SROM.
- The study predicts that tailored doses will achieve therapeutic concentrations quickly and with good patient satisfaction.
- The protocol may improve retention in treatment and reduce reliance on unregulated fentanyl.

## Abstract

Most opioid use disorder (OUD) treatment guidelines target community medical settings, and the subsequent recommendations were established to prioritize safety and reduce diversion prior to the fentanyl era. For people with OUD who use unregulated fentanyl, slow induction onto opioid agonist therapy (OAT) with gradual dose titration is often ineffective or insufficient for reducing withdrawal symptoms and cravings, thereby hampering engagement and retention in treatment. Given the severe risks associated with continued use of the increasingly toxic unregulated drug supply, new and innovative approaches to the management of OUD are urgently needed. We have developed an alternative induction protocol, using a rapid intravenous symptom-inhibiting fentanyl induction (SIFI) to optimize rotation onto oral OAT.

An open-label, single arm, prospective pilot clinical trial is being conducted in an outpatient setting to assess the safety, feasibility, and efficacy of a rapid symptom-inhibiting intravenous fentanyl induction protocol to establish starting doses of methadone or sustained-release oral morphine (SROM) based on individual opioid requirements, as a treatment strategy for individuals with OUD who use unregulated fentanyl. The primary outcome is safety, as defined by occurrence of study drug-related adverse events (including but not limited to opioid toxicity and QT interval prolongation) that require intervention during induction and the first 7 days on OAT. Secondary objectives are to determine whether the SIFI protocol will result in use of higher-than-standard starting doses of methadone and SROM, and to determine whether implementation of this protocol will be acceptable to participants and will result in reduced withdrawal symptoms, improved retention, and better long-term outcomes on OAT.

This is the first study to rapidly and objectively estimate opioid tolerance and use it to calculate individualized starting doses of oral OAT in an outpatient setting among people who use unregulated fentanyl. We predict that starting methadone or SROM with individually-tailored doses will lead to therapeutic target concentrations being achieved quickly, safely, and with good patient satisfaction. This approach has the potential to more effectively and safely initiate OAT, to minimize opioid withdrawal and cravings, and in turn to decrease unregulated fentanyl use and increase retention on life-saving OAT.

ClinicalTrials.gov, NCT05905367; date of registration: June 15, 2023; latest update posted July 18, 2024. https://clinicaltrials.gov/study/NCT05905367

Protocol version: 4.0, April 22, 2024.

The online version contains supplementary material available at 10.1186/s13722-025-00586-7.