In an autistic patient with bipolar disorder who has tics causing a shiver and anxiety, how should lamotrigine be dosed, and is buspirone (Buspar) appropriate for additional anxiety control?

Lamotrigine for Bipolar Disorder in Autism; Buspirone for Anxiety

For an autistic patient with bipolar disorder experiencing tics/shivering and anxiety, lamotrigine should be titrated slowly to 200 mg/day for bipolar maintenance (starting at 25 mg/day, increasing every 2 weeks), and buspirone can be added at low doses (starting 5-10 mg twice daily, maximum 30 mg/day) for anxiety management, as it has demonstrated safety and some efficacy in this specific population.

Lamotrigine Dosing for Bipolar Disorder

Lamotrigine is an established mood stabilizer for bipolar disorder maintenance, particularly effective at preventing depressive episodes 1. The standard titration schedule is critical to minimize serious rash risk (0.1% incidence, including Stevens-Johnson syndrome):

• Week 1-2: 25 mg/day
• Week 3-4: 50 mg/day
• Week 5-6: 100 mg/day
• Week 7+: Target dose 200 mg/day 1

Critical caveat: If the patient is on valproate, lamotrigine doses must be reduced by 50% due to drug interactions 1. Conversely, if on carbamazepine or other enzyme-inducing anticonvulsants, lamotrigine doses may need to be increased 2.

In autism with bipolar disorder specifically, lithium remains the first-line mood stabilizer based on expert consensus 3. However, lamotrigine is a reasonable alternative, particularly given its favorable side effect profile (no weight gain, minimal cognitive effects) 1. Importantly, lamotrigine showed NO efficacy for core autism symptoms in a controlled trial 4, so it should only be used to target the bipolar disorder component.

Buspirone for Anxiety in Autism

Buspirone is an appropriate anxiolytic choice in this population based on several factors:

Evidence Supporting Use:

• A retrospective chart review of 31 youth with high-functioning autism and anxiety showed 58% had significant improvement (CGI-I ≤2) and 29% had mild improvement at a mean dose of 41.6 mg/day 5
• Buspirone was well-tolerated with only 2/31 patients experiencing adverse events (activation, mood lability) 5
• Another case report demonstrated effectiveness for aggressive behaviors in autism at 90 mg/day 6

Dosing Strategy:

• Start: 5 mg twice daily 2
• Titrate: Increase by 5 mg every 3-7 days as tolerated
• Target range: 30-60 mg/day (divided BID or TID) 5, 7
• Maximum: Generally 60 mg/day, though higher doses have been used 6

Key Advantages in This Population:

• No prolactin elevation (unlike antipsychotics) 6
• Does not lower seizure threshold 6
• No behavioral activation typical of SSRIs 8
• No sedation or cognitive impairment 2
• Favorable safety profile with minimal serious adverse events 8

Critical Drug Interaction Warning

If lamotrigine and buspirone are used together, monitor closely but no dose adjustment is typically needed 2. However, be aware that:

• Buspirone is metabolized by CYP3A4 2
• Carbamazepine (if added later) will significantly reduce buspirone levels, requiring dose increases 2
• Conversely, azole antifungals, macrolides, or nefazodone will dramatically increase buspirone levels (up to 50-fold with nefazodone), requiring dose reductions to 2.5 mg daily 2

Addressing the Tics/Shivering

Neither lamotrigine nor buspirone directly treats tics. The "shiver" described may represent:

1. Anxiety-related tremor - which buspirone may help
2. Medication-induced tremor - review current medications
3. True tic disorder - would require separate evaluation and potentially alpha-2 agonists (guanfacine, clonidine) or low-dose antipsychotics 9

The guideline principle is to match specific medications to specific target symptoms rather than expecting one medication to address all symptoms 9.

Monitoring Plan

• Weeks 1-8: Weekly monitoring during lamotrigine titration for rash, mood changes, suicidality
• Ongoing: Monthly assessments using standardized scales (CGI-S, anxiety measures)
• Parental oversight of medication adherence is essential 10
• Watch for: Behavioral activation (more common in younger children with anxiety disorders on any psychotropic) 10

Important Caveats

Autism increases vulnerability to medication side effects 3. Specifically:

• Higher risk of extrapyramidal symptoms with antipsychotics
• Higher risk of activation with antidepressants
• Slower titration is prudent in this population 3

Combination therapy requires clear rationale 9. In this case, the rationale is sound: lamotrigine targets bipolar disorder (particularly depression prevention), while buspirone targets comorbid anxiety - two distinct conditions requiring separate pharmacological approaches 9.