1. Comparison of the respiratory effects of intravenous buprenorphine and fentanyl in humans and rats 
A Dahan, A Yassen, H Bijl, R Romberg, E Sarton, L Teppema, E Olofsen, M Danhof 
British Journal of Anaesthesia 
Volume 94, Issue 6, Pages (June 2005)
DOI: /bja/aei145
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions

2. Fig 1
Calculation of the average drug effect. (1) Baseline ventilation (by definition=1); (2) ventilation normalized by the baseline value; (3) the area between lines 1 and 2 equals the average drug effect; (4) time to end of effect. The average drug effect is divided by the time to end of effect or 420 min if time to end of effect had not been reached within 420 min.
British Journal of Anaesthesia  , DOI: ( /bja/aei145)
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions

3. Fig 2
Individual ventilatory responses after infusion of fentanyl: (a) 1.1; (b) 2.1; (c) 2.9; (d) 4.3; and (e) 7.1 μg kg−1. Ventilation is normalized relative to baseline values. Different symbols and lines depict different subjects.
British Journal of Anaesthesia  , DOI: ( /bja/aei145)
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions

4. Fig 3
Individual ventilatory responses after infusion of buprenorphine: (a) 0.7; (b) 1.4; (c) 4.3; and (d) 8.6 μg kg−1. Ventilation is normalized relative to baseline values. Different symbols and lines depict different subjects.
British Journal of Anaesthesia  , DOI: ( /bja/aei145)
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions

5. Fig 4
Dose–response relationships for (a) fentanyl and (b) buprenorphine. The response is the peak ventilatory depression. The line through the data is the fit to the Hill equation. 0 μg kg−1 is placebo. Data are mean (sd).
British Journal of Anaesthesia  , DOI: ( /bja/aei145)
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions

6. Fig 5
Average drug effect for (a) fentanyl and (b) buprenorphine. Analysis of variance revealed a significant dose effect for fentanyl (P<0.001) but not for buprenorphine. 0 μg kg−1 is placebo. Values are mean (sd).
British Journal of Anaesthesia  , DOI: ( /bja/aei145)
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions

7. Fig 6
Fentanyl dose–response relationship obtained in rats: (a) 5; (b) 10; (c) 15; and (d) 20 min after the initiation of the 20-min fentanyl infusion. A linear dose–response relationship was observed at 5, 10 and 15 min (P=0.01). After 20 min, maximum effect was reached at all fentanyl doses, with no significant differences among fentanyl doses. 0 μg kg−1 is vehicle. Values are mean (sd). To guide the eye, linear regression curves are plotted through the data (continuous line) for times t=5, 10 and 15 min.
British Journal of Anaesthesia  , DOI: ( /bja/aei145)
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions

8. Fig 7
Buprenorphine dose–response relationship obtained in rats: (a) 30; (b) 120; (c) 270; and (d) 390 min after the bolus infusion of buprenorphine. At all measured times a plateau in effect was observed at doses >100 μg kg−1; P<0.01, 100, 300, 1000 and 3000 μg kg−1 vs vehicle; no significant difference was observed among buprenorphine doses. 0 μg kg−1 is vehicle. Values are mean (sd).
British Journal of Anaesthesia  , DOI: ( /bja/aei145)
Copyright © 2005 British Journal of Anaesthesia Terms and Conditions