AUTH/2183/11/08: Merz Pharma v Allergan – misleading potency comparison for Botox vs Xeomin

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Key facts

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Case number	AUTH/2183/11/08
Parties	Merz Pharma UK Ltd v Allergan Ltd
Product(s)	Botox (Allergan); Xeomin (Merz)
Main issue	Alleged representative claims and materials implying Xeomin was ~70% as potent as Botox / dosing ratio 0.7:1, based on animal assay data
Applicable Code year	2008
Complaint received	13 November 2008
Case completed	28 January 2009
Appeal	No appeal
Breach clauses	7.2, 7.3, 7.10, 9.1 and 15.9
Clause 2	Not breached (Panel did not consider it warranted)
Sanctions	Undertaking received; Additional sanctions: Not stated

Reviewed by Dr Anzal Qurbain (FFPM) — ABPI Final Signatory

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Merz (Xeomin) complained that UK Allergan representatives promoting Botox told physicians Xeomin was only ~70% as potent as Botox, including an alleged dosing ratio of 0.7:1.
Merz linked the field reports to Allergan’s use of animal assay potency data (mouse LD50) presented on posters at European meetings and reflected in representative materials (product monograph and an “objection handler”).
Merz argued this messaging conflicted with both products’ SPCs (which stated units were not interchangeable) and could risk patient safety by encouraging higher Xeomin dosing.
Allergan denied briefing the UK sales force to use a fixed ratio and said it did not run promotional activities at the European meetings; it provided UK representative materials for review.
The Panel reviewed Allergan’s product monograph and objection handler, which included comparative potency claims/graphics (eg, Xeomin lots shown at 69/75/78 vs Botox at 95 in a Botox LD50 assay) and statements such as “Botox and Xeomin do not have equivalent potency”.

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On the balance of probabilities, the Panel concluded an Allergan representative had claimed there was a potency difference between the products.
The Panel found the comparative potency messaging was inconsistent with the SPCs’ similar dosing regimens and “units not interchangeable” statements.
The Panel held that animal data had been inappropriately extrapolated to the clinical situation without demonstrating direct relevance and significance.
The product monograph and objection handler were ruled misleading, not substantiated, and not reflective of all the evidence; they would not encourage rational use.
No breach of Clause 2 was ruled (the Panel did not consider the circumstances warranted that level of censure).

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