Very high dilutions of dexamethasone inhibit its pharmacological effects in vivo.

We evaluated the interaction of dexamethasone 10(-17) and 10(-33) M (equivalent to 7cH and 15cH) with dexamethasone in pharmacological concentrations, using as experimental models: acute inflammation induced by carrageenan, Ehrlich ascitic tumour, and migration of tumour infiltrating leukocytes (TIL). Male adult BALB/c mice (n=7 per group) were used in all experiments. Carrageenan (1%) was injected into the footpad for oedema evaluation and into the peritoneal cavity (i.p.), for differential counting of inflammatory cells. Ehrlich ascitic tumour cells (10(7) viable cells/ml) were injected i.p. and tumour cells were counted after 6 days, by the Trypan blue exclusion method. The differential TIL was counted using smears stained by hematoxylin-eosin. Treatments were made immediately after carrageenan inoculation or once a day, during Ehrlich tumour development, until the animals were killed. Animals were treated with the following preparations: (1) phosphate buffer saline (PBS) solution; (2) dexamethasone (0.5 mg/kg for inflammation model or 4mg/kg for tumour model) mixed with dexamethasone 7cH or 15cH; (3) dexamethasone (same doses) mixed in PBS. Homeopathic dexamethasone partially blocked the anti-inflammatory effect of pharmacological dexamethasone with regard to paw oedema (two-way ANOVA, P < 0.0008) and polymorphonuclear cell migration (chi2, P=0.0001). No important differences were observed between experimental and control groups, in relation to Ehrlich tumour cells viability or count, or bodyweight, but potentised dexamethasone restored control levels of TIL viability, compared to mice treated with pharmacological doses of dexamethasone (chi2, P< or = 0.001). The results demonstrate that a potentised substance may change its own pharmacological effects and suggest that ultradilutions effects act mostly on host response.