Table 4.

Total and free plasma concentrations, semen concentrations and total amount of drug in semen for sildenafil and UK-103,320.

Parameter	Sildenafil±s.d.	UK-103,320±s.d.
Total plasma concentration (ng ml−1)
1–2 h	286±117	106±50
4 h	91±36	47±21
Free plasma concentration (ng ml−1)
1–2 h	14.9±4.9	7.0±3.0
4 h	4.2±2.3	2.5±1.2
Total semen concentration (ng ml−1)
1.5 h	51.4±30.1	5.12±3.57
4 h	15.5±5.6	7.10±4.50
Total amount of drug in semen (ng)
1.5 h	188±14.6	17.7±14.7

Arithmetic means reported for all parameters.