The potion was supposed to keep him going even after he was burned out but since he wasn't burned out when he took it it made him swell more than intended and throb thicker inside her than she expected or hoped for. As for his stamina he was doing his best to stay still for her. His hips twitch like he was going to slam inside only for him to force them to relax as he panted.
"Haa so tight and wet haa so hard to mmm hold back." He said and she giggles thinking he was talking about his cum. He wasn't he was talking about holding back his urge to keep fucking her like crazy. Lingering effects of the last potion were being kept by this one and he could remember more of what he did to her in his heat than before.
"Don't hold back" She said thinking of his cum not his thrusts "you feel too good to stop right? Let go and give me everything." She said as she bounced harder. She was still thinking of him cumming when he suddenly grabbed her hips and thrusts sharply into her.
When he did that she cries out as he thrusts hard stuffing her too full only to thrust harder and faster before she could react properly.