TABLE 7.
Drug selectivity for sildenafil and vardenafil at temperatures ranging from 37°C to 20°C.
| Drug selectivity [IC50]/[IC50] | [PDE3-inhibition]/[PDE5-inhibition] | [cAMP-efflux-inhibition]/[cGMP-efflux-inhibition] | [cGMP-efflux-inhibition]/[PDE5-inhibition] | [cAMP-efflux-inhibition]/[PDE3-inhibition] | ||||
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| Temperature | Sildenafil | Vardenafil | Sildenafil | Vardenafil | Sildenafil | Vardenafil | Sildenafil | Vardenafil |
| 37°C | 14400 | 1960 | 0.832 | 1.11 | 815 | 625 | 0.047 | 0.354 |
| 34°C | 6730 | 1650 | 1.61 | 0.620 | 269 | 622 | 0.064 | 0.234 |
| 32°C | 4240 | 2630 | 1.84 | 1.99 | 105 | 422 | 0.046 | 0.320 |
| 28°C | 5780 | 2220 | 0.917 | 1.95 | 180 | 335 | 0.029 | 0.294 |
| 24°C | 5110 | 2510 | − | − | 79.7 | 170 | − | − |
| 20°C | 7270 | 3230 | − | − | 74.5 | 480 | − | − |
Values are ratios between IC50-values for different elimination ways of cAMP and cGMP. Neither of the drugs inhibited cAMP-efflux below 28°C.