Despite her fear and trepidation about the impending shots, a rush of arousal was making her tingle in all the right places. He was standing in front of her holding out his hand, his intense gaze, captivating. Anna felt like she was loosing control of her body as she stepped towards him and allowed him to position her over his knee. The doctor guided her over his lap and carefully secured her hands to the legs of the large office chair that he was now seated in.

"Good girl. Let's make this as easy as possible shall we?"

She took a deep breath when she felt his fingers slip inside the white lace panties she was wearing and ever so gently, he began toying with her wet folds and applying light rhythmic pressure to her clitoris. A new wave of arousal shot down her legs and she gasped as he slid her panties down so that they sat just above her knees, exposing her plump rear.

Once again, Anna felt the doctor part her bottom cheeks and then press his finger against her tight little hole which was still wet with lubricant from when he had taken her temperature earlier.

With a little pressure, one finger slipped inside her anus followed by a second that he smoothly slid into her vagina, which by now, was dripping with her arousal.

Effectively she was now pinned in place by his hand and totally immobilised by his fingers which he had skewered inside both of her most sensitive areas. Anna moaned loudly and curled her toes as the doctor began to manipulate a particularly sensitive area inside her vagina and it wasn't long before little shockwaves of pleasure began to shoot down her legs and she was well on her way towards a powerful climax.

As her breathing became heavier and she started to grind her hips onto his hand in an attempt to get more contact against her clit, the doctor prepared the first injection. He carefully swiped over her bottom with an alcohol wipe and then quickly plunged the thick, 14 gauge, one and a half inch long needle into her perfect unblemished bottom.

Anna screamed as the needle pierced her skin and the doctor began steadily depressing the plunger so that the thick medication was slowly deposited deeply into her muscle. The pain was like a thousand wasps had stung her in unison and she couldn't help but cry out and fight against the bindings that secured her hands to the chair legs.

Meanwhile the Doctor kept working on her swollen clit, steadily building her arousal until once again she found herself teetering on the precipice of orgasm. He removed his fingers from inside her but before Anna had a chance to complain, she felt a large silicone toy penetrate her deeply, blissfully filling her and stretching her to capacity. As soon as the toy was fully lodged inside her, the doctor turned it on and it immediately begin fiercely knocking against her gspot, causing Anna to pant, writhe and grind herself against his knee whilst she whimpered, partly in response to the pain from the injection and partly because she was desperate for release.

Anna felt dizzy with arousal, every fibre of her being was longing for her orgasm and she began pleading with him to allow her to cum but the doctor kept her hanging just on the edge, desperately chasing the distant promise of orgasm to such an extent that she had forgotten about the pain of the antibiotic shot entirely.

Anna didn't notice him wiping the alcohol soaked cotton across her other cheek and she didn't see him pick up the second syringe or aline it with her other perfect cheek.

The shock of the needle breaking through her skin caused Anna to scream and cry uncontrollably, producing a fresh torrent of tears. The doctor held the needle in place allowing her time to compose herself before he depressed the plunger and very slowly, the thick milky serum was deeply forced into her poor aching muscle.

As the seering pain of the double injections continued to burn through her, the doctor began to simultaneously rub her clit and thrust the large dildo in and out of her, slowly removing the throbbing device almost entirely before pumping it back in to her as she panted and moaned. Before long, Anna became aware of the intense burning pain in her bottom mingling with the other good sensations in her sex and it was now adding to her arousal as another wave of pleasure coursed through her and she began to incoherently beg and plead for the doctor to give her release.

"What do you want Anna?"

"I want...."

Despite the level of her vulnerability that the doctor had witnessed she couldn't quite bring herself to say it but he continued to press her gently until she admitted what she wanted.

"I want another shot and I want you to fuck my arse please....."