Restarting Fluoxetine After One-Week Interruption
Direct Recommendation
Restart fluoxetine at the full 60 mg daily dose immediately. 1
Rationale Based on Pharmacokinetics
The one-week interruption is pharmacologically insignificant for fluoxetine due to its exceptionally long half-life:
- Fluoxetine has a half-life of 1–3 days for the parent compound and 4–16 days for its active metabolite norfluoxetine, meaning therapeutic plasma levels persist for weeks after discontinuation 2
- Steady-state concentrations are not reached until approximately 5–7 weeks after a dose change, so one week off represents minimal decline in plasma levels 2
- The long half-life essentially precludes withdrawal phenomena, unlike shorter-acting SSRIs 3
Why Dose Reduction Is Not Necessary
- The FDA label explicitly states that "plasma fluoxetine and norfluoxetine concentration decrease gradually at the conclusion of therapy which may minimize the risk of discontinuation symptoms" 1
- After one week, significant therapeutic concentrations remain in the patient's system—this is not a true "restart" but rather a brief interruption 2
- Fluoxetine 20 mg daily is sufficient for most patients with depression, and this patient was already tolerating and presumably responding to 60 mg 2
Practical Implementation
Resume 60 mg once daily in the morning (fluoxetine is activating and may cause insomnia if taken later) 2
Monitor for:
- Activation symptoms (anxiety, agitation, insomnia) in the first 2–4 weeks, though these are more common with dose increases than continuation 2
- Gastrointestinal symptoms (nausea, diarrhea) which are dose-related but typically emerge early in treatment 4
- Response to treatment should be evident within 2–4 weeks, with maximal benefit by 4–6 weeks 2
Common Pitfall to Avoid
Do not restart at a lower dose (e.g., 20 mg) and re-titrate upward. This approach:
- Unnecessarily delays return to therapeutic dosing 5
- Creates risk of relapse during the re-titration period 5
- Is not supported by the pharmacokinetic profile—the patient still has therapeutic drug levels from the 60 mg dose taken one week ago 2
Special Consideration for This Population
Given the incarceration context, ensure medication adherence monitoring is in place, as the brief interruption suggests potential for future missed doses. The long half-life of fluoxetine provides some protection against the consequences of occasional missed doses compared to shorter-acting SSRIs 3