The three-day rule is a provision of federal regulation that permits practitioners who are not affiliated with an OTP to administer methadone to a patient for the purpose of relieving acute withdrawal symptoms while arranging referral to a licensed program. The allowance is capped at three days, and it cannot be renewed within the same month. In practice, it has historically been used sparingly, because clinicians have worried about safety and because the short window seems ill-suited to overcoming the administrative delays that often accompany OTP enrollment. The new research, published in the journal Addiction Science & Clinical Practice, offers a detailed real-world test of the approach as implemented at the San Francisco General Hospital Bridge Clinic, a low-threshold service designed to meet patients where they are.

The study team, led by Sarah Rosenwohl-Mack of UCSF’s Department of Family and Community Medicine, conducted a retrospective case series covering every patient who initiated methadone under the three-day rule at the Bridge Clinic between June 2024 and July 2025. The setting is notable for an unusual piece of geography: the hospital also houses an opioid treatment program in the same building. When that program could not complete an intake, for example because a patient arrived outside scheduled intake hours or the program was at capacity, staff could refer the person down to the Bridge Clinic, where a dose of methadone could be started immediately under the three-day provision. This bidirectional referral pathway became the study’s central variable.

The researchers tracked two primary outcomes. The first was linkage to an OTP within seven days of receiving the initial Bridge Clinic dose, a window that extends beyond the three-day medication allowance and therefore captures whether the bridge actually carried patients to permanent care. The second was retention in OTP treatment at 30 days, a marker of early stability that addiction medicine researchers view as a meaningful predictor of longer-term benefit. Because methadone carries its own risks, particularly when combined with other sedatives, the team also built in a safety monitoring framework that reviewed urine drug screens, emergency department visits, hospitalizations within seven days, and Medical Examiner overdose reports.

The results are striking for a population that conventional systems routinely lose. Among 166 unique patients who received at least one dose of three-day methadone at the Bridge Clinic, 63 percent, or 104 individuals, successfully linked to an opioid treatment program within seven days. Of those who linked, 62 percent, or 64 patients, were still retained in treatment at the 30-day mark. In a field where attrition between first contact and enrollment has long been considered one of the most stubborn leaks in the continuum of care, the finding suggests that a short bridge of medication can hold a substantial fraction of patients long enough for the formal system to catch up with them.

The most consequential finding, however, concerned the direction of the referral. Using multivariable logistic regression to adjust for other factors, the researchers found that patients who arrived at the Bridge Clinic by referral from the co-located OTP had 3.1-fold higher odds of remaining in treatment at 30 days compared with patients who came through other routes. The interpretation is not that the referral itself dispensed a pharmacological benefit, but that the pathway reflects a coordinated system in which the OTP and the Bridge Clinic function as two doors into the same building of care. A patient handed off from the OTP arrives with an established clinical relationship, a documented treatment plan, and a clear route back, whereas a patient walking in cold must navigate enrollment largely on their own after the three-day window closes.

On the safety side, the record was clean in ways that will reassure clinicians who have hesitated to use the three-day rule. The study identified no methadone-related emergency department visits, no hospitalizations, and no deaths within 30 days of receiving methadone at the Bridge Clinic. The urine drug screen review, designed to flag unexpected results such as methadone positivity in patients not prescribed it or the absence of non-prescribed opioids suggesting diversion, surfaced only one notable case: a single patient who, on closer chart review, turned out to have already been enrolled in methadone treatment elsewhere before receiving a dose at the Bridge Clinic. That finding points to a practical quality-control challenge, ensuring that bridge dosing does not duplicate existing treatment, but it does not undermine the overall safety signal.

The technical logic of the intervention deserves attention. Methadone is a long-acting full mu-opioid receptor agonist with a half-life that supports once-daily dosing, which is precisely why it smooths the cycle of withdrawal and craving that drives much of the daily chaos in untreated opioid use disorder. When a patient presents in withdrawal, the clinical task is to provide enough of the medication to relieve symptoms without accumulating toxicity, which is why Bridge Clinic protocols begin with conservative doses and titrate carefully. The three-day rule fits neatly into this pharmacology: three days of supervised dosing is enough to stabilize a patient physiologically and to interrupt the withdrawal-driven urgency that otherwise pushes people back to fentanyl and other illicit opioids, while the referral machinery works in parallel to secure a permanent slot at an OTP.

The San Francisco team acknowledges intellectual debts in the paper, crediting the Faster Paths Emergency Opioid Withdrawal Protocol at Boston Medical Center, whose published approach informed the local protocol. That lineage matters because it illustrates how low-threshold models are spreading through a kind of open-source clinical adaptation, with programs borrowing and refining each other’s protocols rather than waiting for multi-year trials. The study itself was deemed exempt by the UCSF Institutional Review Board and used retrospectively collected anonymized data, a design that trades the rigor of randomization for the realism of observing how an intervention performs inside the ordinary friction of a public hospital.

The implications reach well beyond one clinic. Opioid treatment programs remain the only legal channel for methadone maintenance in the United States, and their geographic maldistribution means that many counties have no OTP at all. The three-day rule cannot substitute for structural reform, but the study demonstrates that when a low-threshold bridge service and a licensed OTP are deliberately networked, the rule becomes a functional handoff mechanism rather than a rarely used legal footnote. The 3.1-fold retention advantage associated with OTP referral suggests that the return on investment lies in building those connections, ensuring that every bridge dose is paired with a warm pathway back into licensed care. For a lethal epidemic that has proven resistant to conventional outreach, the message is deceptively simple: meet people in withdrawal with medication the same day, and engineer the system so that the door they entered stays open behind them.

Subject of Research: Three-day methadone bridging at a low-threshold clinic to improve linkage and retention in opioid treatment programs

Article Title: Implementing three-day methadone in a low-threshold Bridge Clinic: impact of OTP referral pathways on treatment retention

Article References: Rosenwohl-Mack, S., Suen, L. W., Hart, R., Steiger, S., Hom, J. K., & Snyder, H. (2026). Implementing three-day methadone in a low-threshold Bridge Clinic: impact of OTP referral pathways on treatment retention. Addiction Science & Clinical Practice. https://doi.org/10.1186/s13722-026-00725-8

Image Credits: AI Generated

DOI: 10.1186/s13722-026-00725-8

Keywords: methadone, opioid use disorder, opioid treatment program, Bridge Clinic, three-day rule, treatment retention, harm reduction, San Francisco General Hospital, low-threshold care, withdrawal management, addiction medicine, medication for opioid use disorder