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TL;DRStrength of a medicine (Wirkstärke) is the quantity of active ingredient contained in a defined unit of a medicine, for example 500 mg per tablet, 5 mg/ml of a solution, or 25 micrograms per hour of a patch. It is a defining product-identity attribute.
Three attributes together describe what a medicine actually is: the active ingredient names the substance, the strength states how much of that substance a defined unit carries, and the Darreichungsform (pharmaceutical form) states how it is presented and administered. Change any one of the three and you have a different product. The strength is therefore not a marketing figure but a regulated identity attribute recorded in the marketing authorisation and in the SmPC / Fachinformation, and it is one of the data points a pharmacy, a wholesaler or a market-access team must be able to compare exactly.
The subtlety that trips people up is that the same real amount of active substance can be printed as different numbers. This happens for two independent reasons: the choice of reference (salt versus the active moiety) and the choice of denominator (per dose unit versus per volume versus per pack).
Many active substances are formulated as a salt, an ester or a hydrate, while the therapeutic effect comes from the underlying active moiety, the part of the molecule responsible for the pharmacological action. Regulators increasingly ask that the strength be expressed as the active moiety, so two products containing the identical effective dose can still show different figures depending on which convention the label uses.
| Reason two numbers differ | Example | What is actually equal |
|---|---|---|
| Salt vs active moiety (base) | Amlodipine besilate stated as the salt vs amlodipine stated as the base | The same amount of active moiety (amlodipine) is delivered |
| Per dose unit vs per volume | 250 mg per 5 ml stated as "250 mg" vs "50 mg/ml" | Identical concentration, different denominator |
| Per dose unit vs per total pack | 100 mg per tablet, 20 tablets, vs "2000 mg total" | Same tablet strength, pack total is a derived figure |
To make strengths machine-comparable across borders, the units themselves are standardised under ISO 11240, the units-of-measurement standard within the ISO IDMP suite. ISO 11240 specifies rules for the coded representation of units so that "5 mg/ml", "5 milligram per millilitre" and regional spellings all map to one unambiguous coded unit. Alongside it, the concept of a reference strength and the active moiety let two labelled strengths be reconciled to a common basis, which is exactly what is needed when comparing a salt-based figure against a base-based one. Because the strength is bound to the substance, it also connects to the substance-level identity captured in the Wirkstoffdossier.
An identical strength is one of the statutory criteria for aut-idem substitution. Under §129 Abs. 1 Satz 2 SGB V a pharmacy may hand out a different manufacturer's product only if it is, in the words of the statute, "in Wirkstärke und Packungsgröße identisch", licensed for the same indication, and of the same or an interchangeable dosage form. A product may not be substituted at a different strength.
The strength is equally central to reference pricing. Membership of a Festbetragsgruppe (reference-price group) under §35 SGB V is built on comparable active ingredient, dosage form and strength, so that a fixed reimbursement amount applies to genuinely comparable products. This is what makes the strength economically load-bearing: it decides which products a Generikum competes against, and it defines the like-for-like set against which prices are compared. Getting the strength expression wrong, for example comparing a salt figure against an active-moiety figure, would silently distort both the substitution set and the price comparison.
On pharmazie.com the strength is one of the article identity attributes carried per PZN, drawn from the licensed ABDA article master data. It sits in the base-data section next to the active ingredient, dosage form and pack size, and it is one of the fields whose change can trigger a new PZN, because a different strength is, for identification purposes, a different article.
One honest limitation: the stored strength is the labelled article-master-data value as licensed. It does not by itself resolve whether a salt-based and an active-moiety-based figure describe the same effective dose. That reconciliation depends on the reference convention in each product's authorisation, so treat the field as a precise identity attribute and a research aid, not as an automatic equivalence ruling between two differently expressed strengths.
