ATCvet code: QD07 CC01

Betamethasone valerate is a potent synthetic corticosteroid (dexamethasone-analogue) with anti-inflammatory and anti-pruritic activity when applied topically as well as mild mineralocorticoid properties.

Fusidic acid hemihydrate has a steroidal structure but does not possess any steroid-like effects. It belongs to the class of antibiotics called Fusidanes. Fusidic acid hemihydrate acts by prohibiting the protein synthesis of bacteria when it binds to elongation factor G (required for translocation on the bacterial ribosome after peptide bond formation during protein synthesis).

Its action is largely bacteriostatic, but at high concentrations (2 to 32-fold higher than the MIC) the effect may be bactericidal. Fusidic acid hemihydrate has activity against Gram‑positive bacteria, namely Staphylococcus spp. (particularly S. pseudintermedius) including penicillinase producing species. It is also active against streptococci.

Pathogenic bacteria	Fusidic acid Sensitive / Resistant	Fusidic acid MIC
Gram-positive bacteria
- Staphylococcus pseudintermedius	Sensitive	MIC90≅ 0.25-4 µg/ml
- Streptococcus spp.us	Sensitive	MIC90≅ 8-16 µg/ml
- Corynebacteria spp.	Sensitive	MIC90 ≅ 0.04 – 12.5 µg/ml
Gram-negative bacteria
- Pseudomonas spp.	Resistant	>128 µg/ml
- E.Coli	Resistant	>128 µg/ml

Data based on studies conducted mainly in Europe but also in North America between 2002 and 2011.

Two major mechanisms of resistance to fusidic acid hemihydrate have been reported in S. aureus – the alteration of the drug target site which is due to chromosomal mutations in FusA (encoding elongation factor EF-G) or FusE encoding ribosome protein L6, and the protection of the drug target site by FusB family proteins, including fusB, fusC, and fusD. The fusB determinant originally was found on the plasmid in S. aureus but has also been found on a transposon-like element or in a staphylococcal pathogenicity island.

No cross-resistance between fusidic acid hemihydrate and other antibiotics that are in clinical use has been identified.

In vitro data obtained from a study on dog skin indicate that 17 % of the applied dose of betamethasone and 2.5 % of the applied dose of fusidic acid hemihydrate are absorbed over 48 hours after the administration of the product to the skin.

Betamethasone valerate is absorbed after topical application. Absorption after administration to inflamed skin is likely to be greater. Following systemic absorption betamethasone can cross the blood-brain barrier, the blood‑placenta barrier and, in small amounts, may pass into the milk of lactating animals.