How does the potency vary among different commercial preparations of botulinum toxin (BoNT)?

Updated: Oct 10, 2019
  • Author: Divakara Kedlaya, MBBS; Chief Editor: Elizabeth A Moberg-Wolff, MD  more...
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The different preparations of BoNT-A, onabotulinumtoxinA (BOTOX®; Allergan; Irvine, Calif), abobotulinumtoxinA (Dysport®; Ipsen; Paris, France), incobotulinumtoxinA (Xeomin®; Merz Pharmaceuticals, Frankfurt, Germany), prabotulinumtoxinA (Jeuveau®; Evolus Inc, Santa Barbara, Calif), CS-BOT (Chiba Serum Institute; Chiba, Japan), and Chinese BTX-A (Prosigne ®; Lanzhou Biological Products Institute, China) differ in potency. [6]

  • BoNT-A is prepared by laboratory fermentation of C botulinum cultures. Crude botulinum toxin is a protein with a molecular weight of about 190,000 Daltons. After purification, the toxin is diluted with human serum albumin, bottled in vials, lyophilized (freeze-dried), and sealed.

  • Each freeze-dried vial containing 100 units (U) of BoNT-A is reconstituted with preservative-free normal saline (1-5 mL) just before use. The manufacturer recommends that the toxin be used within 4 hours of reconstitution.

  • The potency of BoNT-A is measured in mouse units (MU). One MU of BoNT-A is equivalent to the amount of toxin that kills 50% of a group of 20 g Swiss-Webster mice within 3 days of intraperitoneal injection (LD50).

  • According to one report, 1 nanogram of toxin contains approximately 20 U of BOTOX® (ie, 1 U of BOTOX® is equal to approximately 0.05 nanogram of the toxin).

  • According to another report comparing the 3 different preparations of BoNT-A, 1 nanogram of Dysport contains approximately 40 MU, whereas 1 nanogram of the BOTOX® contains approximately 4 MU, and 1 nanogram of CS-BOT contains approximately 15.2 MU.

  • Median paralysis unit (MPU) is thought to be a more pharmacologically relevant unit of biologic activity. Comparison of the potency ratio based on the MPU values for Dysport and BOTOX® revealed a 2.44-fold difference in potency between these formulations. [7]

  • LD50 of BoNT-A for a 70-kg adult male has been calculated to be 2500-3000 U (35-40 U/kg).

  • Minimum lethal dose of BoNT-B in monkeys is 2400 U/kg.

  • Clinically, 1 U of BoNT-A (BOTOX®) is approximately equivalent to 3 U of Dysport®. [8]

  • Studies of Xeomin® and Prosigne® use unit dosing comparable (1:1) with BOTOX®. [9, 10]

  • An animal study that found that Xeomin® contains the highest specific neurotoxin activity, followed by Dysport®, with BOTOX® having the lowest specific activity. [11]

  • Standardization efforts are underway using measurements of the toxin's pharmacologically relevant actions (eg, median paralysis unit).

  • BOTOX® vials contain sodium chloride (0.9 mg) and human albumin (0.5 mg), and the protein load is 5 ng/100 units; Prosigne® vials contain porcine gelatin (5 mg), dextran (25 mg), and sucrose (25 mg), and the protein load is 4-5 ng/100 units of BoNT-A. [12] BOTOX® is thought to be about 1.5 times more potent than Prosigne®.

  • BoNT-B is marketed in the United States as RimaBotulinumB (MyoBloc®). This preparation is a ready-to-use solution that does not require reconstitution; it is available in 3 vial sizes (ie, 2500 U, 5000 U, and 10,000 U) and is stable for up to 21 months in refrigerator storage.

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