How to manage muscle stiffness and bruxism in patients taking Vyvanse (lisdexamfetamine)?

Managing Muscle Stiffness and Bruxism in Patients Taking Vyvanse

Amphetamines, including lisdexamfetamine (Vyvanse), are known to potentially induce or aggravate bruxism, and management requires either dose adjustment, addition of specific medications to counteract these side effects, or consideration of alternative ADHD treatments.

Understanding the Problem

Amphetamines are well-documented as medications with the potential adverse effect of bruxism 1. Lisdexamfetamine is a prodrug that converts to d-amphetamine in the blood, which increases dopamine and noradrenaline concentrations in the synaptic cleft 2. This dopaminergic activity is likely responsible for the muscle-related side effects including bruxism and muscle stiffness 3.

Step 1: Verify Dosing is Appropriate

Before adding additional medications, ensure the Vyvanse dose is not excessive:

• Maximum recommended dose: The total daily dose for amphetamines should not exceed 40 mg 4
• Proper titration: Starting dose should be 10 mg once daily, increased gradually by 5-10 mg increments at weekly intervals 4
• Key principle: If the top recommended dose does not provide adequate symptom control, more is not necessarily better, and higher doses increase the risk of adverse effects including cardiovascular effects and tolerance 4

If the patient is on an appropriate dose and still experiencing these side effects, proceed to pharmacological management.

Step 2: Pharmacological Management of Bruxism

First-Line Option: Low-Dose Quetiapine

Low-dose quetiapine (25-50 mg daily) is the most evidence-based option for managing stimulant-induced bruxism:

• Quetiapine acts as a 5-HT2 receptor antagonist, which can counteract the serotonergic contribution to bruxism 5
• In case series, patients with SSRI-induced bruxism (similar mechanism to stimulant-induced) reported resolution of symptoms within a few days of starting quetiapine 25-50 mg daily 5
• This dose is well below the typical antipsychotic range and is generally well-tolerated

Alternative Options for Bruxism

If quetiapine is not suitable or ineffective, consider these alternatives that have shown potential to ameliorate bruxism 1:

• Clonazepam: Benzodiazepine with muscle relaxant properties, though use caution given addiction potential
• Gabapentin: May help with both muscle tension and bruxism; starting dose 100-300 mg at bedtime, titrated as tolerated 6
• Buspirone: Anxiolytic with potential anti-bruxism effects
• Clonidine: Alpha-2 agonist that may reduce stimulant-related side effects

Important caveat: The evidence for these alternatives is largely based on case reports and small studies, making quetiapine the most systematically studied option for this specific indication 1, 3.

Step 3: Managing Muscle Stiffness

For muscle stiffness specifically (separate from bruxism):

• Gabapentin can address both neuropathic-type discomfort and muscle tension; initiate at 100-300 mg at bedtime or three times daily, increase by 100-300 mg every 1-7 days as tolerated, up to 3600 mg/day in divided doses 6
• Avoid traditional muscle relaxants (cyclobenzaprine, carisoprodol, methocarbamol) as their effects are nonspecific and not truly related to muscle relaxation; they may increase fall risk without addressing the underlying stimulant-induced muscle tension 6

Step 4: Non-Pharmacological Interventions

While adding medications to counteract side effects:

• Dental protection: Recommend a custom night guard to prevent tooth damage from bruxism
• Timing adjustment: Consider taking Vyvanse earlier in the day if symptoms worsen in the evening
• Hydration and magnesium: Ensure adequate hydration and consider magnesium supplementation (though evidence is limited)

Step 5: When to Consider Switching Medications

If symptoms persist despite the above interventions:

• Switch to alternative stimulant: Consider methylphenidate-based medications, which may have a different side effect profile 6
• Consider non-stimulant ADHD medications: Atomoxetine or guanfacine, though note that atomoxetine itself has been reported to potentially induce bruxism 1

Common Pitfalls to Avoid

• Do not simply increase the Vyvanse dose thinking it will help—higher doses worsen these side effects 4
• Do not prescribe traditional muscle relaxants like cyclobenzaprine (which is structurally similar to amitriptyline) without recognizing they don't truly address muscle spasm and carry significant side effects 6
• Do not ignore the problem—untreated bruxism can result in severe tooth destruction, temporomandibular joint damage, myofascial pain, and headaches 3
• Monitor for worsening symptoms as experimental studies show that mandibular bracing and thrusting can evoke muscle pain, fatigue, tension, and stiffness 7