What are the typical starting doses for medications used to treat mental illness, such as selective serotonin reuptake inhibitors (SSRIs) like fluoxetine, benzodiazepines like alprazolam, and antipsychotics like risperidone, in an adult patient with no significant medical history?

Medications for Mental Illness: Starting Doses

Selective Serotonin Reuptake Inhibitors (SSRIs)

For fluoxetine, start at 10 mg every other morning (or 10 mg daily) in adults, with a maximum of 20 mg daily for most patients. 1

• Fluoxetine is activating with a very long half-life (1-3 days for fluoxetine, 4-16 days for norfluoxetine), meaning side effects may not manifest for several weeks 1, 2
• Morning dosing is preferred to minimize insomnia risk 1
• Doses of 20-60 mg have been used in clinical trials, but 20 mg/day is sufficient for most patients 2

Paroxetine should be initiated at 10 mg per day, with a maximum of 40 mg per day (morning or evening). 1

• Paroxetine is less activating but more anticholinergic than other SSRIs 1

Sertraline starts at 25-50 mg per day, with a maximum of 200 mg per day (morning or evening). 1

• Sertraline is well tolerated and has less effect on metabolism of other medications compared to other SSRIs 1

Citalopram begins at 10 mg per day, with a maximum of 40 mg per day. 1

• Well tolerated, though some patients experience nausea and sleep disturbances 1

Critical SSRI Considerations

• Exercise caution with fluoxetine, fluvoxamine, and paroxetine when combining with other medications due to potent CYP450 enzyme inhibition 3
• CYP2D6 poor metabolizers have 3.9 to 11.5-fold higher fluoxetine levels and require starting doses of 10 mg daily with cautious titration 2
• Typical side effects include sweating, tremors, nervousness, insomnia or somnolence, dizziness, gastrointestinal disturbances, and sexual dysfunction 1

Benzodiazepines

Alprazolam starts at 0.25 mg at bedtime, with a range of 0.25-4.0 mg, though the usual recommended dose is 0.5-2.0 mg 30 minutes before bedtime. 1

• Short-acting benzodiazepines like alprazolam carry risks of tolerance and paradoxical agitation in approximately 10% of patients 4
• Concurrent benzodiazepine use with opioids increases overdose death risk nearly four-fold 4
• Abrupt withdrawal can cause rebound anxiety, hallucinations, seizures, delirium tremens, and rarely death 4
• When tapering is necessary, reduce the dose by 25% every 1-2 weeks 4

Lorazepam for acute anxiety or agitation: 0.25-0.5 mg PRN orally or sublingually for rapid onset, with lower doses minimizing sedation while providing anxiolytic effects. 4

• Maximum daily dosage typically should not exceed 2 mg lorazepam equivalent 4
• Frequency should be limited to not more than 2-3 times weekly for PRN use 4
• Benzodiazepines should be time-limited (days to weeks) to avoid tolerance and dependence 4

Atypical Antipsychotics

Risperidone for acute psychosis or mania: start at 0.5-2.0 mg/day for agitated dementia with delusions, 1.25-3.5 mg/day for late-life schizophrenia, or 2 mg/day as initial target dose for psychotic features. 3, 4

• Risperidone in combination with lithium or valproate is effective for acute mania 4
• Dose-response curves follow a hyperbolic pattern, with maximally efficacious average dosages around 5 mg/day risperidone equivalents for schizophrenia 5

Olanzapine for acute mania or psychosis: 5.0-7.5 mg/day for agitated dementia, 7.5-15 mg/day for late-life schizophrenia, or 10-15 mg/day for acute mania. 3, 4

• Olanzapine 10-20 mg/day combined with lithium or valproate is superior to mood stabilizers alone for acute mania 4
• Avoid in patients with diabetes, dyslipidemia, or obesity due to severe metabolic profile 3, 4

Quetiapine starts at 50-150 mg/day for agitated dementia, 100-300 mg/day for late-life schizophrenia, or 50-250 mg/day for mania with psychosis. 3, 4

• Quetiapine is first-line for patients with Parkinson's disease 3
• Quetiapine plus valproate is more effective than valproate alone for adolescent mania 4

Aripiprazole for acute mania: 5-15 mg/day, with a favorable metabolic profile compared to olanzapine. 4

• Aripiprazole has low lethality in overdose, making it safer when suicide risk is a concern 4

Antipsychotic Monitoring Requirements

• Baseline monitoring should include body mass index, waist circumference, blood pressure, fasting glucose, and fasting lipid panel 4
• Follow-up monitoring: BMI monthly for 3 months then quarterly; blood pressure, glucose, and lipids at 3 months then yearly 4
• Avoid clozapine, olanzapine, and conventional antipsychotics in patients with diabetes, dyslipidemia, or obesity 3
• Avoid clozapine, ziprasidone, and conventional antipsychotics in patients with QTc prolongation or congestive heart failure 3

Mood Stabilizers

Lithium for bipolar disorder: start at 150 mg per day in elderly patients, with target levels of 0.8-1.2 mEq/L for acute treatment. 1, 4

• Blood levels of 0.2-0.6 mEq/L are generally adequate for elderly patients and usually achieved with 150-300 mg per day 1
• Baseline monitoring requires complete blood count, thyroid function tests, urinalysis, BUN, creatinine, serum calcium, and pregnancy test in females 4
• Ongoing monitoring every 3-6 months should include lithium levels, renal and thyroid function, and urinalysis 4
• Lithium reduces suicide attempts 8.6-fold and completed suicides 9-fold 4

Valproate (Depakote): initial dosage 125 mg twice daily, titrate to therapeutic blood level (40-90 mcg/mL or 50-100 μg/mL). 4

• Baseline monitoring requires liver function tests, complete blood count, and pregnancy test 4
• Ongoing monitoring every 3-6 months should include serum drug levels, hepatic function, and hematological indices 4
• Valproate is particularly effective for irritability, agitation, aggressive behaviors, and mixed or dysphoric mania 4

Lamotrigine for maintenance therapy in bipolar disorder: requires slow titration to minimize risk of Stevens-Johnson syndrome. 4

• Critical safety requirement: never rapid-load lamotrigine 4
• If discontinued for more than 5 days, restart with full titration schedule rather than resuming previous dose 4
• Lamotrigine is particularly effective for preventing depressive episodes in bipolar disorder 4

Other Antidepressants

Bupropion (Wellbutrin): 37.5 mg every morning, then increase by 37.5 mg every 3 days, with a maximum of 150 mg twice daily. 1

• Activating with possible rapid improvement of energy level 1
• Should not be used in agitated patients and those with seizure disorders 1
• To minimize insomnia risk, give second dose before 3 p.m. 1

Mirtazapine (Remeron): 7.5 mg at bedtime, with a maximum of 30 mg at bedtime. 1

• Potent and well tolerated; promotes sleep, appetite, and weight gain 1

Critical Pitfalls to Avoid

• Never use antidepressant monotherapy in bipolar disorder due to risk of mood destabilization, mania induction, and rapid cycling 4
• Avoid typical antipsychotics (haloperidol, fluphenazine) in young patients due to 50% risk of tardive dyskinesia after 2 years of continuous use 4
• Do not combine clozapine with carbamazepine, ziprasidone with tricyclic antidepressants, or low-potency conventional antipsychotics with fluoxetine 3
• Systematic medication trials require 6-8 weeks at adequate doses before concluding an agent is ineffective 4
• Maintenance therapy should continue for at least 12-24 months after mood stabilization; withdrawal of lithium dramatically increases relapse risk within 6 months 4