As-Needed Medication for Depression is Not Appropriate
Depression requires continuous daily antidepressant therapy, not PRN (as-needed) dosing, because antidepressants work through sustained neurochemical changes that take weeks to develop and must be maintained consistently to prevent relapse. 1
Why PRN Dosing Fails for Depression
- Antidepressants require 4-8 weeks of continuous daily use at therapeutic doses to achieve initial response, making PRN administration pharmacologically ineffective 1
- The mechanism of action depends on sustained receptor modulation and neuroplastic changes that cannot occur with intermittent dosing 1
- Treatment must continue for 4-9 months after achieving response in first-episode depression to prevent relapse, requiring uninterrupted daily administration 1
Evidence-Based Treatment Algorithm
Initial Treatment Phase
- Start a second-generation antidepressant (SSRI or SNRI) at full therapeutic doses taken daily 1, 2
- Monitor closely at 1-2 weeks after initiation for suicidal ideation, agitation, or behavioral changes 1
- Assess therapeutic response at 6-8 weeks; if inadequate response, modify treatment by switching medications or adding psychotherapy 1, 2
Continuation Phase
- After achieving satisfactory response, continue daily antidepressant therapy for minimum 4-9 months 1, 2
- For patients with ≥2 prior episodes, maintenance treatment should continue ≥1 year or longer to reduce relapse risk 2
- Premature discontinuation leads to high relapse rates, as depression frequently returns when partially treated 3
Common Pitfalls to Avoid
- Never prescribe antidepressants PRN - this represents a fundamental misunderstanding of antidepressant pharmacology and guarantees treatment failure 1
- Avoid stopping treatment prematurely when patients feel better; the risk for relapse is highest in the first months after response 1, 3
- Do not use inadequate doses - treatment failure often results from subtherapeutic dosing rather than medication selection 3
- Recognize that 38% of patients do not respond to initial SSRI treatment within 6-12 weeks, requiring systematic treatment modification rather than PRN dosing 2
What About Anxiety Medications?
While benzodiazepines can be used PRN for acute anxiety, depression itself cannot be treated this way 1. If a patient has comorbid anxiety with depression, the antidepressant must still be taken daily, with possible short-term PRN anxiolytics as adjunctive therapy only 1.