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Yohimbe bark extract (Pausinystalia johimbe)


Yohimbe bark extract (Pausinystalia johimbe) Image
Synonyms / Common Names / Related Terms
Aphrodien, Corynanthe johimbi, Corynanthe yohimbi, corynine, johimbi, Pausinystalia johimbe, Pausinystalia yohimbe, quebrachine, Rubiaceae (family), yohimbehe, yohimbehe cortex, yohimbeherinde, yohimbene, yohimbime, yohimbine, P.johimbe (Schumann) Beille.





Mechanism of Action

Pharmacology:

  • Constituents: Yohimbe bark extract contains approximately 6% indole alkaloids, of which 10-15% is yohimbine. A 1995 chemical analysis of 26 commercial yohimbe products reported that most commercial yohimbe products contained virtually no yohimbine.1 The pharmacological activity of yohimbine has been well characterized in studies, although these effects may or may not apply to yohimbe, depending on the concentration of yohimbine present.
  • Alpha-2 Adrenergic Antagonist Effects: Yohimbine acts as an alpha-2 adrenoceptor antagonist. It is significantly more active at presynaptic adrenoceptors than postsynaptic receptors. This action blocks the decrease in central noradrenergic response and blocks the reduction in peripheral sympathetic activity.11,12,13,8,9,14,6 In 1975, Papeschi and Theiss demonstrated the dopamine antagonistic properties and serotonin-like properties of yohimbine.15
  • Yohimbine also inhibits monoamine oxidase, blocks calcium channels, and blocks peripheral serotonin receptors.
  • Genital blood vessel dilation, nerve impulse transmission to genital tissue and increased reflex excitability in the sacral region of the spinal cord appear to be responsible for yohimbine's aphrodisiac activity. Yohimbine is most effective for impotence in men with organic vascular dysfunction. Yohimbine's effects on impotence are mediated through increased penile blood flow and increased central excitatory impulses to the genital tissue.16,17
  • A clinical randomized control study demonstrated that yohimbine does not influence the function of the alpha-2 adrenoceptors on adipocytes, and does not facilitate weight loss, as previously thought.2,18
  • Platelet Aggregation Inhibition: Yohimbine has been found to inhibit epinephrine-induced platelet aggregation ex vivo; the lowest dose of yohimbine that significantly inhibited platelet aggregation was 8mg.10
  • Norepinephrine Effects: Yohimbine acts centrally to increase sympathetic outflow, and peripherally to increase the release of norepinephrine from adrenergic nerve terminals. This increases the plasma norepinephrine, and elicits pressor effects.5,7,19,20,4
  • Hormonal Effects: Yohimbine was demonstrated to produce an increase in plasma prolactin levels in rats.21 This study suggested that the increased prolactin levels were not caused by anti-dopaminergic effects, and possibly occurred through a mechanism related to prolactin-releasing factor. Yohimbine has been reported to possess mild anti-diuretic effects, possibly due to stimulation of hypothalamic centers and release of pituitary hormones.
  • Insulin Effects: In a study of type 1 and type 2 diabetic rats, pretreatment with yohimbine potentiated glucose-induced insulin release in non-diabetic control rats, and an improvement of oral glucose tolerance in type 2 diabetic rats, but not in type 1 diabetic rats. Yohimbine may act via blockade of postsynaptic alpha-2 adrenoceptors to produce insulinotropic and hypoglycemic effects.22

Pharmacodynamics/Kinetics:

  • Bioavailability: Yohimbine's oral absorption appears to be poor, although there appears to be highly variable bioavailability. This may be the result of extensive first-pass metabolism.23 Yohimbine displays dose-related increases in area under the curve (AUC).24,23 There is a significant correlation between plasma norepinephrine levels and yohimbine AUC or Cmax.23 According to one pharmacokinetic study, a 10mg oral dose of yohimbine produced a peak plasma concentration within 45 minutes and the half-life for plasma clearance was 0.2-1.1 hours. Yohimbine is fairly lipophilic and it crosses the blood-brain barrier.25 Since alpha-adrenoceptors are located in widespread locations throughout the central and peripheral nervous system, yohimbine has a variety of autonomic and psychic effects (increased noradrenaline release). As a result, yohimbine was shown to induce lipid mobilization in obese subjects.3 In a single-dose study of yohimbine in young healthy, older healthy and Alzheimer's patients, the authors found that the plasma disposition of yohimbine displayed large variability with no significant differences among subject groups. However, the Cmax and AUC of the active metabolite, 11-hydroxy-yohimbine, were significantly lower in the older normal subjects then in the young normal or Alzheimer's patients. They also found a strong positive correlation between cerebrospinal fluid (CSF) and plasma yohimbine concentrations and a weak positive correlation between CSF and plasma concentrations of 11-hydroxy-yohimbine.26
  • Elimination: Yohimbine has an elimination half-life of less than 1 hour, while an active metabolite, 11-hydroxy-yohimbine, has a half-life of about 6 hours.23 In a study of 32 patients, 24 displayed one-compartment elimination while 8 displayed two-compartment elimination.23 Less than 1% of the oral dose was recovered unchanged in the urine within 24 hours.25

References

  1. Betz JM, White KD, der Marderosian AH. Gas chromatographic determination of yohimbine in commercial yohimbe products. J AOAC Int 1995;78(5):1189-1194. 7549534
  2. Berlin I, Stalla-Bourdillon A, Thuillier Y, et al. [Lack of efficacy of yohimbine in the treatment of obesity]. J Pharmacol 1986;17(3):343-347. 3795978
  3. Berlan M, Galitzky J, Riviere D, et al. Plasma catecholamine levels and lipid mobilization induced by yohimbine in obese and non-obese women. Int J Obes 1991;15(5):305-315. 1885256
  4. Mosqueda-Garcia R, Fernandez-Violante R, Tank J, et al. Yohimbine in neurally mediated syncope. Pathophysiological implications. J Clin Invest 1998;102(10):1824-1830. 9819368
  5. Owen JA, Nakatsu SL, Fenemore J, et al. The pharmacokinetics of yohimbine in man. Eur J Clin Pharmacol 1987;32(6):577-582. 3653227
  6. Cameron OG, Zubieta JK, Grunhaus L, et al. Effects of yohimbine on cerebral blood flow, symptoms, and physiological functions in humans. Psychosom Med 2000;62(4):549-559. 10949101
  7. Biaggioni I, Robertson RM, Robertson D. Manipulation of norepinephrine metabolism with yohimbine in the treatment of autonomic failure. J Clin Pharmacol 1994;34(5):418-423. 8089252
  8. Charney DS, Heninger GR, Sternberg DE. Assessment of alpha 2 adrenergic autoreceptor function in humans: effects of oral yohimbine. Life Sci 1982;30(23):2033-2041. 6287139
  9. Bagheri H, Berlan M, Montastruc JL, et al. Yohimbine and lacrimal secretion. Br J Clin Pharmacol 1990;30(1):151-152. 2390426
  10. Berlin I, Crespo-Laumonnier B, Cournot A, et al. The alpha 2-adrenergic receptor antagonist yohimbine inhibits epinephrine-induced platelet aggregation in healthy subjects. Clin Pharmacol Ther 1991;49(4):362-369. 2015726
  11. Goldberg MR, Robertson D. Yohimbine: a pharmacological probe for study of the alpha 2- adrenoreceptor. Pharmacol Rev 1983;35(3):143-180. 6140686
  12. Anden NE, Pauksens K, Svensson K. Selective blockade of brain alpha 2-autoreceptors by yohimbine: effects on motor activity and on turnover of noradrenaline and dopamine. J Neural Transm 1982;55(2):111-120. 6294237
  13. Anonymous. Yohimbine: time for resurrection? Lancet 1986;2(8517):1194-1195. 2877331
  14. Galitzky J, Taouis M, Berlan M, et al. Alpha 2-antagonist compounds and lipid mobilization: evidence for a lipid mobilizing effect of oral yohimbine in healthy male volunteers. Eur J Clin Invest 1988;18(6):587-594. 2906290
  15. Papeschi R, Theiss P. The effect of yohimbine on the turnover of brain catecholamines and serotonin. Eur J Pharmacol 1975;33(1):1-12. 1175676
  16. Wagner G, Saenz dT, I. Update on male erectile dysfunction. BMJ 1998;316(7132):678-682. 9522795
  17. Balon R. The effects of anitdepressants on human sexuality: Diagnosis and management update 1999. Primary Psychology 1999;6(11):40-54.
  18. Berlin I, Crespo-Laumonnier B, Turpin G, et al. The alpha-2 adrenoceptor antagonist yohimbine does not facilitate weight loss but blocks adrenaline induced platelet aggregation in obese subjects. Therapie 1989;44(4):301. 2595649
  19. Grossman E, Rea RF, Hoffman A, et al. Yohimbine increases sympathetic nerve activity and norepinephrine spillover in normal volunteers. Am J Physiol 1991;260(1 Pt 2):R142-R147. 1847020
  20. Dwoskin LP, Neal BS, Sparber SB. Evidence for antiserotonergic properties of yohimbine. Pharmacol Biochem Behav 1988;31(2):321-326. 3244710
  21. Meltzer HY, Simonovic M, Gudelsky GA. Effect of yohimbine on rat prolactin secretion. J Pharmacol Exp Ther 1983;224(1):21-27. 6294278
  22. Abdel-Zaher AO, Ahmed IT, El Koussi AD. The potential antidiabetic activity of some alpha-2 adrenoceptor antagonists. Pharmacol Res 2001;44(5):397-409. 11712871
  23. Sturgill MG, Grasing KW, Rosen RC, et al. Yohimbine elimination in normal volunteers is characterized by both one- and two-compartment behavior. J Cardiovasc Pharmacol 1997;29(6):697-703. 9234649
  24. Grasing K, Sturgill MG, Rosen RC, et al. Effects of yohimbine on autonomic measures are determined by individual values for area under the concentration-time curve. J Clin Pharmacol 1996;36(9):814-822. 8889902
  25. Piletz JE, Segraves KB, Feng YZ, et al. Plasma MHPG response to yohimbine treatment in women with hypoactive sexual desire. J Sex Marital Ther 1998;24(1):43-54. 9509380
  26. Le Corre P, Dollo G, Chevanne F, et al. Biopharmaceutics and metabolism of yohimbine in humans. Eur J Pharm Sci 1999;9(1):79-84. 10494000




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