Time-dependent influence of procaine hydrochloride on cisplatin antitumor activity in P388 tumor bearing mice.

In previous papers (1,2) we demonstrated that procaine hydrochloride may increase the therapeutic index of cisplatin by an improvement of its antitumor activity and a reduction of its nephrotoxicity. In the present study we investigated the relationship between the antitumor activity obtained by cisplatin associated with procaine hydrochloride and the relative time of administration of these two agents. When procaine hydrochloride (40 mg/Kg body wt) was administered 30 or 120 minutes before cisplatin (16 mg/kg) diluted in normal saline (i.e. clinical condition) it increased, although not significantly, its percent increase in life span (%ILS) and cure rate (%ILS: +292 and +217 vs +150; cure rate: 46.2% and 42.3% vs 23%, respectively), compared to cisplatin alone treatment. These results became statistically significant when procaine hydrochloride was given either simultaneously with cisplatin or 30 and 120 minutes thereafter (%ILS: > 400 vs +150; cure rate: 65.4%, 73.1% and 68% vs 23%, respectively). In conclusion procaine hydrochloride increased the antitumor activity of cisplatin independently from its timing of administration, although it seemed to be a better potentiating agent when administered after cisplatin.