Medication Summary
The goal of pharmacotherapy is reduction of abnormal muscle contractions. Botulinum toxin type A is the treatment of choice. [16, 17] Carbamazepine, benzodiazepines, and baclofen may also be used in patients who refuse BTX injections or who are not surgical candidates.
Neuromuscular Blockers, Botulinum Toxins
Class Summary
Botulinum toxin type A is the drug of choice. [16, 17] It causes presynaptic paralysis of the myoneural junction and reduces abnormal contractions. Therapeutic effects may last 3-6 months.
Botulinum toxin type B is useful in reducing excessive, abnormal contractions associated with blepharospasm [18] ; binds to receptor sites on the motor nerve terminals and after uptake inhibits release of acetylcholine, blocking transmission of impulses in neuromuscular tissue; 7-14 d after administering initial dose, assess patients for a satisfactory response; increase doses 2-fold over previously administered dose for patients who experience incomplete paralysis of the target muscle.
OnabotulinumtoxinA (BOTOX)
OnabotulinumtoxinA (BOTOX) is useful in reducing excessive, abnormal contractions associated with blepharospasm. It binds to receptor sites on the motor nerve terminals and, after uptake, inhibits the release of acetylcholine, blocking transmission of impulses in neuromuscular tissue. At 7-14 days after administration of the initial dose, assess patients for a satisfactory response. Increase the dose 2-fold over the previously administered dose in patients who experience incomplete paralysis of the target muscle.
RimabotulinumtoxinB (Myobloc)
When botulinum toxin injection is indicated and type A toxin is ineffective, injection with type B toxin (rimabotulinumtoxinB [Myobloc]) should be considered.
AbobotulinumtoxinA (Dysport)
AbobotulinumtoxinA (Dysport) binds to receptor sites on the motor nerve terminals and, after uptake, inhibits release of acetylcholine, blocking transmission of impulses in neuromuscular tissue. At 7-14 days after administration of the initial dose, assess the patient for a satisfactory response. Increase the dose 2-fold over the previously administered dose in patients who experience incomplete paralysis of the target muscle.
IncobotulinumtoxinA (Xeomin)
Xeomin, a botulinum toxin type A product, may be used if Botox proves unsuccessful, or is unavailable. It should produce satisfactory results, though systematic trials of Xeomin for HFS have not yet been reported. Excess administration will produce undesirable weakness and facial asymmetry.
Benzodiazepines
Class Summary
Benzodiazepines may potentiate the effects of gamma-aminobutyric acid (GABA) and facilitate inhibitory GABA neurotransmission. It may act in the spinal cord to induce muscle relaxation. Treatment needs to be individualized for each patient.
Clonazepam (Klonopin)
Clonazepam (Klonopin) is useful in suppressing muscle contractions by facilitating inhibitory GABA neurotransmission and other inhibitory transmitters.
Skeletal Muscle Relaxants
Class Summary
Muscle relaxants may inhibit the transmission of monosynaptic and polysynaptic reflexes at the spinal cord level.
Baclofen (Lioresal, Gablofen)
Baclofen (Lioresal) may induce hyperpolarization of afferent terminals and inhibit both monosynaptic and polysynaptic reflexes at the spinal level.
Anticonvulsants
Class Summary
Anticonvulsants are used to manage severe muscle spasms and provide analgesia and mild sedation. Anticonvulsants are probably the best medications in terms of efficacy and long-term safety when botulinum toxin and surgery are not options.
Carbamazepine (Tegretol, Equetro, Epitol, Carbatrol)
Carbamazepine (Tegretol) is effective in the treatment of hemifacial spasm and complex partial seizures. It appears to act by reducing polysynaptic responses and blocking posttetanic potentiation. Once a response is attained, attempt to reduce the dose to the minimum effective level or discontinue the drug at least once every 3 months. In patients who cannot tolerate carbamazepine, consider oxcarbazepine (dosage not yet established).
Oxcarbazepine (Trileptal, Oxtellar XR)
Oxcarbazepine (Trileptal) is effective in partial complex epilepsy. It shows promise in hemifacial spasm. Oxcarbazepine may be considered when first-line agents (eg, botulinum toxin, carbamazepine) have failed or are contraindicated.
