Common (>10% in pediatric trials):

• Somnolence — 16% (vs 4% placebo) — the dominant complaint; can be activity-limiting
• Decreased appetite (~7–8%)
• Headache
• Fatigue
• Nausea
• Vomiting
• Insomnia (paradoxically — somnolence in some, insomnia in others)
• Irritability

Less common (1–10%):

• Increased blood pressure + heart rate (modest, but real — class effect of NRIs)
• Constipation
• Decreased libido
• Diaphoresis
• Dry mouth
• Lethargy / sluggish cognition
• Nasopharyngitis (likely incidental, but listed at ~10% in long-term extension)

Rare-serious (<1% but worth knowing):

• Suicidal ideation/behavior — FDA BLACK BOX WARNING (all ages): 0.9% incidence in pediatric trials (n=1019) vs 0.4% placebo; 1.6% in adult trials (n=189) vs 0% placebo. The signal is small in absolute terms but statistically real. Most concerning: this is one of the few ADHD medications with a black-box specifically for suicidal ideation, and the warning applies to all ages — not just <25yo as with general antidepressants.
• Mania/hypomania activation in undiagnosed bipolar — class-typical for NE-pushing agents
• Hypertensive episodes — monitor BP/HR in cardiovascular-risk patients
• Hepatic enzyme elevation — case-level reports; LiverTox classifies as low-grade hepatotoxicity risk
• Serotonin syndrome if combined with other serotonergic agents at high doses (theoretical but plausible given multimodal 5-HT activity)

Specific watch periods:

• First 4 weeks: Suicidal-ideation watch (highest risk during initiation)
• First 8 weeks: Mood activation (mania, agitation, severe insomnia)
• Ongoing: BP/HR monitoring; hepatic check at 6–8 weeks if any abdominal symptoms