onabotulinumtoxinA

Action

Blocks neuromuscular transmission by binding to receptor sites on motor nerve terminals and inhibiting acetylcholine release, thereby causing localized muscle denervation. As a result, local muscle paralysis occurs, which leads to muscle atrophy and reinnervation due to development of new acetylcholine receptors.

Availability

Toxin type A-(onabotulinumtoxinA)

Powder for injection: 100 units/vial

Toxin type A-abobotulinumtoxinA

Freeze-dried powder for injection: 300 units/vial, 500 units/vial

Toxin type A-(incobotulinumtoxinA)

Powder for injection, lyophilized: 50 units in single-use vials, 100 units in single-use vials

Toxin type B-(rimabotulinumtoxinB)

Solution for injection: 5,000-units/ml vial

Indications and dosages

Toxin type A (onabotulinumtoxinA)

➣ Temporary improvement in appearance of moderate to severe glabellar lines associated with corruga-tor or procerus muscle activity

Adults ages 65 and younger: Botox cosmetic only-Total of 20 units (0.5-ml solution) injected I.M. as divided doses of 0.1 ml into each of five sites: two in each corrugator muscle and one in procerus muscle. Injection usually needs to be repeated q 3 to 4 months to maintain effect. Dysport-50 units I.M. in five equal aliquots of 10 units each to achieve clinical effect

Xeomin-Or, 20 units per treatment session divided into five equal I.M. injections of 4 units each.

➣ Treatment of blepharospasm in patients previously treated with onabotulinumtoxinA (Botox)

Adults: Xeomin-When initiating therapy, base dose, number, and location of injections on the previous dosing of onabotulinumtoxinA (Botox). If previous dose of Botox isn't known, the recommended starting dose is 1.25 to 2.5 units per injection site.

➣ Upper limb spasticity

Adults: Botox-75 to 360 units I.M. divided among selected muscles at a given treatment session. Dose can be repeated no sooner than 12 weeks after the previous injection.

➣ Prophylaxis of headaches in patients with chronic migraine (15 or more days per month with headache lasting 4 hours a day or longer)

Adults: Botox-155 units as 0.1-ml (5 units) injections per each site divided across seven head and neck muscles

➣ Severe axillary hyperhidrosis inadequately managed by topical agents

Adults: Botox-50 units per axilla injected into defined hyperhidrotic area

➣ Blepharospasm

Adults: 1.25 to 2.5 units injected into medial and lateral pretarsal orbicularis oculi of upper eyelid and lateral pretarsal orbicularis oculi of lower eyelid

➣ Strabismus

Adults: 1.25 to 5 units injected into eyelid (dosage varies with strabismus severity). Dose can be repeated in 7 to 14 days if patient has adequate response; with inadequate response, dosage may be doubled.

Toxin types A and B (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, rimabotu-linumtoxinB)

➣ Treatment of cervical dystonia to decrease severity of abnormal head position and neck pain in both botulinum toxin-naïve and previously treated patients

Adults: Xeomin-120 units injected I.M. into affected muscles per treatment session.

➣ To relax skeletal muscles and reduce severity of abnormal head position and neck pain associated with cervical dystonia

Adults: Botox-Usual dosage is 236 units injected I.M. locally into affected muscles. Dosage ranges from 198 to 300 units. Dysport-500 units I.M. as a divided dose among affected muscles in patients with or without a history of prior treatment with botulinum toxin.

Myobloc-2,500 to 5,000 units I.M. injected locally into affected muscles.

Contraindications

• Hypersensitivity to drug or its components

• Allergy to cow's-milk protein (Dysport)

• Acute urinary tract infection or acute urinary retention (Botox intradetrusor injections)

• Active infection at injection site

Precautions

Use cautiously in:

• cardiovascular disease, peripheral neuropathy, neuromuscular disorders, compromised respiratory function, dysphagia

• inflammation at injection site, injections near vulnerable anatomical structures

• pregnant or breastfeeding patient

• children younger than age 12; children younger than age 18 (Dysport, Xeomin)

Administration

• Be aware that only trained professional medical personnel should inject this drug.

• Be aware that botulinum toxin products aren't interchangeable.

Toxin type A (onabotulinumtoxinA) when administered for eye disorders

• Reconstitute by slowly injecting preservative-free normal saline solution into drug vial.

• Rotate vial gently to mix drug; then draw up at least 20 units (0.5-ml solution) and expel air bubbles.

• Remove needle used for reconstitution, and attach 30G needle. Then inject drug as divided doses of 0.1 ml into each of five sites (two in each corruga-tor muscle, one in procerus muscle).

• Prepare eye with several drops of local anesthetic and ocular decongestant, as prescribed, several minutes before injection for blepharospasm or strabismus.

• When administering for upper limb spasticity, dilute with preservative-free normal saline solution to 200 units/4 ml or 100 units/2 ml. Then, using a 25G to 30G needle for superficial muscles and a longer 22G needle for deeper musculature, inject no more than 50 units per site.

Toxin type A (abobotulinumtoxinA)

• Reconstitute each 300-unit vial with 0.6 ml preservative-free normal saline solution and each 500-unit vial with 1 ml preservative-free normal saline solution.

• Swirl vial gently to mix drug.

• Remove needle used for reconstitution. Use a 23G to 25G needle for administration. Then inject 10 units into each of five sites (two in each corrugator muscle and one in the procerus muscle).

• Use within 4 hours of reconstitution.

Toxin type B (rimabotulinumtoxinB)

• Draw up prescribed dose from preservative-free, 3.5-ml single-use vial.

• Don't shake vial.

• Divide prescribed dose and inject locally into affected muscles.

Adverse reactions

CNS: headache, dizziness

CV: hypertension, arrhythmias, myocardial infarction (MI)

EENT: blepharoptosis, conjunctivitis, keratitis, eye dryness, double vision, tearing, increased sensitivity to light, sinusitis, pharyngitis

GI: nausea, dyspepsia, difficulty swallowing

Musculoskeletal: back pain, neck pain, muscle weakness

Respiratory: pneumonia, bronchitis, upper respiratory tract infection

Skin: skin tightness, ecchymosis

Other: tooth disorder, injection site redness, edema, or pain, flulike symptoms, facial muscle paralysis, infection, anaphylaxis

Interactions

Drug-drug. Aminoglycosides, anticholinesterase compounds, clindamycin, lincomycin, magnesium sulfate, other neuromuscular blockers (such as succinylcholine), polymyxin B, quinidine: increased risk of adverse effects

Patient monitoring

• Stay alert for signs and symptoms of anaphylaxis, particularly after first dose.

• Monitor vital signs and ECG, watching for evidence of hypertension, arrhythmias, and MI.

• Assess effect of drug on affected muscles; check for paralysis.

See Be aware that spread of toxin effects may lead to swallowing and breathing difficulties and death. Provide immediate medical attention if respiratory, speech, or swallowing difficulties occur.

• Monitor temperature. Watch for signs and symptoms of respiratory and EENT infections as well as flulike symptoms.

Patient teaching

See Instruct patient to seek immediate medical attention if respiratory, speech, or swallowing difficulties occur.

• Teach patient about desired effect of injection. Advise patient to report paralysis.

• Instruct patient to report signs and symptoms of infection, particularly flulike illness and EENT and respiratory infections.

• Inform patient being treated for ble-pharospasm (uncontrollable blinking) that he may experience transient eyelid drooping, corneal inflammation, double vision, dry eyes, tearing, and light sensitivity.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs mentioned above.