Modulation of NSAID-induced antinociceptive and anti-inflammatory effects by α2-adrenoceptor agonists with gastroprotective effects

Tizanidine, an alpha2-adrenergic receptor agonist with myospasmolytic action, is indicated for the treatment of back pain either as monotherapy or in combination with nonsteridal anti-inflammatory drugs (NSAIDs). Tizanidine (0.25-1.0 mg/kg) significantly produced analgesic and anti-inflammatory effect in acetic acid induced writhing in mice and carrageenan-induced paw edema in rats, respectively. The effects were comparable with clonidine (0.25 and 0.50 mg/kg), another alpha2-agonist. Yohimbine (1 mg/kg), alpha2-adrenergic antagonist reversed the effect of tizanidine. Tizanidine (0.25 mg/kg) and clonidine (0.25 mg/kg) significantly potentiated the antinociceptive and anti-inflammatory effect of NSAIDs (nimesulide, meloxicam and naproxen). Tizanidine (1 mg/kg) did not alter basal pH, acidity (free and total) of gastric content and did not produce any mucosal injury in fasted rats. Tizanidine (1 mg/kg) significantly reduced meloxicam (UD50 3.21 mg/kg), nimesulide (UD50 24.52 mg/kg) and naproxen (UD50 14.10 mg/kg)-induced ulcerogenic effect (ulcer index, pH and free/total acidity). It is expected that tizanidine exerted gastrotprotection through stimulation of gastric and central alpha2-adrenergic receptors. Present investigation suggested that tizanidine not only enhance the analgesic and anti-inflammatory effect of NSAIDs but also improved gatstrointestinal tolerability of NSAIDs through modulation of central alpha-2-receptors. From this study, it can be speculated that tizanidine and NSAID combination therapy would prove to be a novel approach to treat nociceptive/inflammatory conditions with improved gastric tolerability of NSAIDs.

Mirtazapine, yohimbine or olanzapine augmentation therapy for serotonin reuptake-associated female sexual dysfunction: a randomized, placebo controlled trial

BACKGROUND

Many agents have been proposed as potential treatments for SSRI-associated sexual dysfunction, but few placebo-controlled trials have been reported.

METHOD

After a 1-month baseline evaluation, pre-menopausal women with moderate to severe sexual dysfunction associated with the institution of fluoxetine therapy were randomized to augmentation therapy with placebo (N=39), mirtazapine (N=36), yohimbine (N=35) or olanzapine (N=38) for a 6-week period. Outcomes were measured using a daily diary, a biweekly self-report assessment, and a computer assisted structured interview.

RESULTS

At baseline, orgasm was most severely impaired. After 6 weeks, there was statistically significant improvement on most measures for the overall group of patients, however there were few differences between treatment groups. Isolated treatment differences were observed for the patient self-report of overall sexual function (olanzapine superior to placebo) and the structured interview sexual satisfaction item (mirtazapine inferior to placebo).

CONCLUSION

No drug assessed was consistently associated with differences from placebo. The results of the study do not support uncontrolled reports of efficacy for these agents in premenopausal women.

Yohimbine-induced withdrawal and anxiety symptoms in opioid-dependent patients

BACKGROUND

Alteration in noradrenergic regulation as well as alteration in the hypothalamic-pituitary-adrenal (HPA) axis have been associated with opioid dependence and acute abstinence symptoms.

METHODS

This double-blind, placebo-controlled study evaluated subjective, physiologic, and biochemical responses to yohimbine (.4 mg/kg, IV) in eight patients receiving methadone and compared results to those from a pool of nine healthy volunteers. All subjects were compared for panic anxiety symptom scale (PASS) scores, systolic and diastolic blood pressure, heart rate, plasma 3-methoxy-4 hydroxyphenethyleneglycol (MHPG), and cortisol.

RESULTS

Yohimbine elicited objective and subjective opioid withdrawal and elevated craving for opioid drugs in methadone patients. Significant yohimbine effects were seen across the combined subject group for PASS, physiologic measures, MHPG, and cortisol. Methadone patients had lower baseline MHPG levels. Methadone group interactions with yohimbine were seen for systolic blood pressure and cortisol levels.

CONCLUSIONS

Methadone-maintained patients are sensitive to the postsynaptic effects of noradrenergic-facilitating medications, experiencing greater physiologic and psychological symptoms, including an increase in craving. The effect on cortisol supports the above conclusion and is consistent with HPA axis perturbation in opioid dependence as reported in other studies and extends these observations to stable methadone-maintained patients. Medications that increase synaptic noradrenaline should be used with care in opioid-dependent patients.

[Effect of almitrine/raubasine on cerebral metabolism in the elderly]

Recent neurobiological data has led to renewed interest in oxygen (O2). The discovery of neuroglobin, protein varyingly present in the brain, has been enhanced by the elucidation of the mechanisms through which oxygen intervenes in neuronal metabolism. Almitrine/raubasine activates the metabolism of hypoxic/ischemic neurones by increasing O2 bioavailability. This mechanism supports the effects on behaviour obtained in various animal models and the benefits observed during clinical trials in elderly patients presenting with cognitive defects.

Yohimbine treatment of organic erectile dysfunction in a dose-escalation trial

Yohimbine has had questionable effects in men with organic erectile dysfunction. We conducted this study to better define the population of men responsive to yohimbine, because tobacco was thought to affect a regimen of yohimbine more than other risk factors. We measured nocturnal penile tumescence with the RigiScan monitor, hormone profiles, answers to the Florida Sexual Health Questionnaire, and clinical responses at baseline and after two different doses of yohimbine in 18 nonsmoking men with erectile dysfunction. Of the 18 men, nine (50%) were successful in completing intercourse in more than 75% of attempts. The yohimbine responders were men with less severe erectile dysfunction as manifested by improved increased rigidity on RigiScan testing, higher Florida Sexual Health Questionnaire scores, and slightly higher levels of serum testosterone. Yohimbine is an effective therapy to treat organic erectile dysfunction in some men with erectile dysfunction.

Dietary supplements and other alternative medicines for erectile dysfunction. What do I tell my patients?

Dietary supplements and other alternative medicines have enjoyed a tremendous amount of popularity and use over the past decade. Although, the prevalence of these therapies for erectile dysfunction (ED) is unknown at this time, numerous media outlets and alternative medicine publications seem to support the utilization of these therapies for ED. The placebo effect is approximately 25% (1 out of 4 benefit) from past randomized trials of FDA approved medications for ED. Adequate clinical trials are needed for dietary supplements for ED to access whether or not a benefit beyond a placebo effect exists. Clinicians should become aware of these supplements and the current research espousing or discouraging their use, and they should understand the adverse effects associated with them in order to effectively discuss these products with any patient inquiring about them.

Orthostatic hypotension in patients with Parkinson's disease: pathophysiology and management

Orthostatic hypotension is common in elderly patients, and is now considered to be an important prognostic factor for cognitive decline and mortality. In patients with Parkinson's disease, the prevalence of symptomatic orthostatic hypotension may be as high as 20%. Two factors could explain this high prevalence. First, dopaminergic drugs may induce or worsen orthostatic hypotension. Secondly, Parkinson's disease is a cause of primary autonomic failure with an involvement of the peripheral autonomic system as shown by the ubiquitous distribution of Lewy bodies and reduced iobenguane [metaiodobenzylguanidine (MIBG)] cardiac uptake. These pathological and pharmacological characteristics clearly differentiate autonomic failure of Parkinson's disease from multiple system atrophy. If autonomic abnormalities appear to be present from the first stage of the disease, early onset (within the first year) of symptomatic orthostatic hypotension in the course of parkinsonism can be considered as an exclusion criteria for idiopathic Parkinson's disease. No specific clinical trials have evaluated the effects of antihypotensive drugs in patients with Parkinson's disease and thus no specific therapeutic strategy can be recommended. The management of orthostatic hypotension in patients with Parkinson's disease should always start with patient education and nonpharmacological treatment. Drug therapy should be reserved for symptomatic patients who do not get benefit from nonpharmacological management. Among the available drugs, alpha1-adrenergic agonists (mainly midodrine) or plasma volume expanders (mainly fludrocortisone) are the most frequently used. There are also some drugs that are currently investigational such as yohimbine and droxidopa. Other drugs such as desmopressin or octreotide may be of interest in some situations. Domperidone is widely used in patients with parkinsonism with no proven effect on orthostatic hypotension.

The potential antidiabetic activity of some alpha-2 adrenoceptor antagonists

The effect of alpha-2 adrenoceptor antagonists, yohimbine and efaroxan, on the plasma glucose and insulin levels was studied in non-diabetic control, type-I (insulin-dependent) and type-II (non-insulin-dependent) diabetic rats. Pretreatment with either yohimbine or efaroxan potentiated glucose-induced insulin release in non-diabetic control rats and produced an improvement of the oral glucose tolerance and potentiated glucose-induced insulin release in type-II but not in type-I diabetic rats. Treatment with either yohimbine or efaroxan reduced the plasma glucose level and increased the plasma insulin level of non-diabetic control and type-II diabetic rats but not of type-I diabetic rats. Effects of efaroxan were more marked. Pretreatment of non-diabetic control and type-II diabetic rats with either yohimbine or efaroxan inhibited clonidine-induced hyperglycaemia and suppressed or reversed clonidine-induced hypoinsulinaemia. Also, pretreatment of these animals with either yohimbine or efaroxan enhanced the hypoglycaemic and insulinotropic effects of glibenclamide. The combination of glibenclamide and efaroxan led to a synergistic increase in insulin secretion, while that of glibenclamide and yohimbine led to an additive increase. The hyperglycaemic effect of diazoxide in non-diabetic control and type-II diabetic rats was inhibited by pretreatment with either yohimbine or efaroxan. The hypoinsulinaemic effect of diazoxide in these animals was antagonized and reversed by pretreatment with yohimbine and efaroxan, respectively. In type-I diabetic rats, there was no change in the plasma glucose and insulin levels induced by the treatment of animals with each of clonidine or diazoxide alone or in combination with either yohimbine or efaroxan. Glibenclamide produced a slight decrease in the plasma glucose level of type-I diabetic rats, at the end of the 120 min period of investigation but there was no change in the plasma insulin level. Pretreatment of these animals with either yohimbine or efaroxan produced no change in glibenclamide effects. Additionally, bath application of efaroxan or glibenclamide inhibited the relaxant effects of different concentrations of diazoxide on the isolated norepinephrine-contracted aortic strips, while the application of yohimbine produced insignificant changes. The combination of glibenclamide and efaroxan led to complete inhibition of the relaxant effects of different concentrations of diazoxide, while that of glibenclamide and yohimbine did not produce such an effect. It is concluded that yohimbine, via blockade of postsynaptic alpha-2 adrenoceptors, and efaroxan, via blockade of postsynaptic alpha-2 adrenoceptors and adenosine triphosphate-sensitive potassium channels in the pancreatic beta-cell membrane, produce insulinotropic and subsequent hypoglycaemic effects.

Creative-dynamic image synthesis: a useful addition to the treatment options for impotence

In contrast to the impressive advances made in somatic research on erectile dysfunction, psychogenic erectile dysfunction is usually treated as a monolithic block. In this study, we evaluated the erectogenic power of creative-dynamic image synthesis in men with psychogenic erectile dysfunction. Sixty-nine men with a mean age of 46 y, suffering from erectile dysfunction of no known organic cause, were entered in a placebo-controlled study in which the erectogenic power of imagination, yohimbine and a placebo were compared. There was a significant difference between the subjective results of creative-dynamic image synthesis (75% increase of potency) and those achieved through treatment with the drug yohimbine (55% increase in potency) and with a placebo (30% increase in potency). Creative-dynamic image synthesis is a potent initiator of erections in men with psychogenic erectile dysfunction, has no known side effects and is very cost-effective.

Yohimbine in erectile dysfunction: would an orphan drug ever be properly assessed?

The systemic use of adrenergic antagonists in the treatment of sexual dysfunction has originated more controversy than results. Among the various agents, yohimbine has acquired an unenviable reputation in the treatment of erectile dysfunction. The drug is pharmacologically well characterized as an alpha2 adrenoceptor antagonist with activity in the central and peripheral nervous systems. In-depth, systematic studies in animals have shown that yohimbine has a remarkable positive effect on sexual performance. Meta-analyses of the few controlled, randomized human studies have consistently shown an advantage of yohimbine over placebo. Despite such a long history and encouraging activity, the drug has not yet been subjected to scientifically rigid human clinical trials. Although relevant basic pharmacological and animal research information has been available for over 15 years, recent studies have been designed with a lack of insight and complete disregard of those fundamental studies. Currently, dose-response investigations are not available, alternative routes of administration (i.e., sublingual) have not been investigated, nor has continuous versus "on-demand" administration been explored. Synergistic activity with other drugs was last studied nearly four decades ago. Assessments of various populations were carried out in very limited cohorts and only in the most general terms. In short, properly designed trials in humans have not been performed. This apparent lack of scientific and financial interest has various roots. First of all, yohimbine is an old drug. As such it does not enjoy patent protection or commercial viability. Until molecular/formulation changes can be brought about (as recently happened with two other venerable agents: phentolamine and apomorphine) serious investigation of the drug will remain in limbo. Another promising avenue is the potential for synergistic effect of yohimbine with other compounds. When all is said and done, it could be that the naysayers are right and yohimbine indeed lacks clinical activity as a treatment for the phallodynamically challenged. As long as it remains an orphan drug we will never know. One hopes that interest can be eventually generated for the proper assessment of yohimbine in a different formulation or in combination with other agents.

Neuropeptide Y in obese women during treatment with adrenergic modulation drugs

BACKGROUND

The aim of the study is the assessment whether weight loss treatment with adrenergic modulation drugs modifies neuropeptide Y (NPY) plasma concentration in obese women.

MATERIAL AND METHODS

13 obese women (BMI 38.3 +/- 4.4) were tested before and subsequently 10 and 20 days after weight loss treatment. The treatment consisted of a very low caloric diet of 400 kcal (1670 kJ) daily combined with ephedrine with caffeine (E + C) or ephedrine with caffeine and yohimbine (E + C + Y) administered for 10 days using the cross-over method. The patients underwent physical examination, including heart rate and blood pressure measurements, spectral heart rate variability (HRV) at rest and after 3 minute handgrip and a 15 minute cycloergometer exercise at 75 W. All the above mentioned tests were carried out thrice in each patient. In 13 obese patients and in 6 control women plasma NPY concentrations were determined by a specific radioimmunoassay using rabbit anti-NPY antiserum and a standard synthetic porcine NPY (Peninsula Lab.).

RESULTS

Plasma NPY concentrations were significantly lower in the obese persons compared with the control group. During weight loss treatment with adrenergic modulation drugs no changes in plasma NPY were found at rest and after physical exercise. Also no differences in HRV indices were observed.

CONCLUSIONS

1. Low plasma NPY concentration observed in obesity may be a contraregulatory factor that could prevent further weight increase. 2. Weight reduction treatment did not affect plasma NPY concentration and cardiovascular response to physical exercise. 3. The doses of adrenergic modulation drugs used in our study did not induce any serious side effects, and were so low that no change of plasma NPY concentration and cardiovascular responses were observed at rest.

Effects of yohimbine on the antinociceptive and place conditioning effects of opioid agonists in rodents

1. The pharmacological modulation of opioid actions by drugs acting on heterologous mechanisms could be useful to overcome some of the main problems associated with the use of opiate agonists. Based on previous findings on the interactions between yohimbine and opioid drugs, we have further studied the effects of yohimbine on the antinociceptive and positive-negative reinforcing effects of morphine (mu opioid receptor-preferring agonist), U-50,488 (kappa agonist) and SNC80 (delta agonist). 2. Pretreatment with yohimbine completely blocked the antinociception provided by the three opioid agonists in the mouse tail-immersion test. 3. A similar blockade of SNC80 and U-50,488-induced antinociception was observed with yohimbine in the mouse hot plate test at the same doses. In this paradigm, the effect of the kappa agonist was very slight and the actions of yohimbine rather variable. 4. In place conditioning experiments with SD (Sprague -- Dawley) male rats, yohimbine alone was inactive but it limited the preference induced by morphine and SNC80 and the aversive effect of U-50,488. Impaired novelty preference was also observed with the combination of yohimbine and U-50,488. 5. It is concluded that yohimbine tends to limit opioid antinociception and the addictive potential of mu and delta opioid agonists. More selective drugs could help to understand the mechanisms involved in these actions.

Efficacy of 1.25% amitraz solution in the treatment of generalized demodicosis (eight cases) and sarcoptic mange (five cases) in dogs

Eight dogs with generalized demodicosis and five with sarcoptic manage were treated with 1.25% amitraz solution applied weekly and associated with an antidote treatment (atipamezol, 0.1 mg kg-1 i.m. once: and yohimbine 0.1 mg kg-1 once daily for 3 days, orally). Results of skin scrapings were used to determine whether therapy should be continued or stopped. The median number of treatments for demodicosis and sarcoptic mange was three (range 2-5) and two (range 1-3), respectively. Some side-effects were observed but all were stopped with antidote treatment; no failure or relapses occurred at 6-36 months after treatment.

Pharmacological features of an almitrine-raubasine combination. Activity at cerebral levels

Treatment with the combination of almitrine-raubasine increases both arterial oxygen partial pressure and haemoglobin oxygen saturation, reflecting an actual increase in the oxygen content of arterial blood. Furthermore, at the trans-cerebral carotid artery/internal jugular vein level, the treatment increases cerebral arterio-venous oxygen and glucose differences, suggesting an actual increase both in oxygen and glucose availability and uptake in cerebral tissues. The increased glucose transfer to the brain is supported also by enhancement of the 3H-deoxyglucose uptake induced by drug pre-treatment both in normoxia and hypoxia. Both almitrine and raubasine act at cerebral mitochondrial levels by decreasing the 'loss' of the 'biological' free energy for phosphorylation supported by the age-related drop in the cerebral enzyme activities, such as phosphofructokinase, pyruvate dehydrogenase and citrate synthase. Furthermore, the components interfere with the alterations induced by peroxidative stress acting at the level of cytochrome c, cytochrome c oxidase and succinate dehydrogenase. Treatment with the combination almitrine-raubasine increases the concentration of noradrenaline metabolites, while alteration of the dopaminergic system is less important. The interference with the noradrenergic system is possibly linked to the electroencephalographic changes induced by drug treatment: increasing alpha-rhythm distribution and reactivity, and increases in beta-rhythm amplitude. Pharmacological effects of almitrine-raubasine, obtained in experimental conditions, correlate with clinical therapeutic efficacy, e.g., in the treatment of cognitive disorders associated with ageing and other cerebral and neurosensory impairments. It is difficult to summarise, in a few pages, the large number of papers related to the cerebral pharmacometabolic and pharmacodynamic activities of the almitrine-raubasine combination. Thus, this review presents in sequential steps some of the interrelated research in humans and laboratory animals which describes in a critical way preclinical to clinical results.

Stroke and functional rehabilitation: the Chinese experience

According to an epidemiological study of cerebrovascular disease carried out in China in 1986, the prevalence, incidence, and mortality rates were 159.93/100,000, 115.61/100,000, and 31.33/100,000, respectively. These figures were high compared to available epidemiological data for the rest of the world. This highlights the fact that, as in other countries, functional rehabilitation after stroke is an important medical and social need in China. Clinical experience shows that within a few hours to a few months after a stroke, a large proportion of patients spontaneously experience partial, or on occasion, complete recovery from neurologic symptoms. However, functional rehabilitation in medical care units is required because it assists in and accelerates the recovery of impaired function. Almitrine-raubasine has been used to improve functional rehabilitation after stroke for some time in China. By enriching the oxygen content of arterial blood, it brings more oxygen to the cerebral tissues and therefore promotes cerebral aerobic metabolism during ischemia. In the acute phase of stroke, positron emission tomography showed, in man, that almitrine-raubasine helps normalize the ischemic penumbra area, as shown by an improvement in the coupling between oxygenation and perfusion. Long after stroke, single photon emission computed tomography showed that almitrine-raubasine restores normal cerebral vasodilator response to acetazolamide. With a view to further documenting the clinical efficacy of almitrine-raubasine on the convalescent period of patients with cerebrovascular disease, a double-blind, placebo-controlled study is planned. One hundred patients with ischemic cerebrovascular disease in the territory of the carotid artery will be included 4-6 weeks after the acute onset. Two tablets daily of almitrine-raubasine or placebo will be prescribed for 3-6 months. Before treatment, there will be a 2-week washout period for all other drugs, except for antihypertensive and antidiabetic drugs. In addition to complete clinical monthly examinations, neurological functional deficit scores, Barthel index, Hasagawa Dementia scales, and CT scan are scheduled. The study results should confirm those reported in the scientific literature: although untreated patients may show spontaneous improvement, almitrine-raubasine should accelerate patients' functional rehabilitation.

Clinical efficacy of almitrine-raubasine. An overview

Different pharmacological properties of almitrine-raubasine show that this combination may be a good therapy for the treatment of age-related cerebral disorders and functional rehabilitation after stroke. Many clinical studies have been carried out in France and in the rest of Europe, confirming the value of this compound in such situations. Without discussing the complexity of clinical trials in both the areas of cognitive disorders and stroke, we shall present two studies demonstrating the beneficial effects of almitrine-raubasine against cognitive impairments. The first is a double-blind controlled study versus placebo with a 3-month follow-up period involving patients (aged between 60 and 85) with memory loss, lack of concentration, impaired mental altertness, and emotional instability. The second is a controlled multicenter study of 155 outpatients (age 70-85) presenting with cognitive decline (assessed by MMSE, SCAG). In both these studies, almitrine-raubasine significantly improved symptomatology and was superior to placebo, especially in the vascular cases. This confirms the validity of previous studies and justifies the indication of these compounds in the treatment of age-related cognitive disorders. Other studies also demonstrated the beneficial effect of this compound on neurosensory vascular disorders, with specific studies carried out on chorioretinal dysfunctions (visual symptomatology) and in vestibular disorders (vertigo associated with electronystagmographic modifications). The appropriate and usual dosage (2 tablets per day) and the good tolerance of the compound have been confirmed in a French multicentric study in 5,361 outpatients.

Selectivity of oxymetazoline for urethral pressure vs blood pressure in the anaesthetized female rabbit

OBJECTIVE

The aim of this study was to test alpha-adrenergic reference agonists for tissue selectivity in the urethra and to pharmacologically characterize the functional alpha-adrenoceptor type of the female rabbit urethra in vivo.

MATERIAL AND METHODS

The effect of alpha-adrenergic agonists and antagonists on the urethral pressure was compared with that on blood pressure and heart rate measured simultaneously in the anaesthetized female rabbit.

RESULTS

Oxymetazoline, NS-49, phenylephrine and phenylpropanolamine enhanced the urethral pressure in a dose-dependent manner. Phenylephrine and phenylpropanolamine also enhanced the blood pressure with significantly lower ED50 (dose that gives half of the maximal enhancing effect) values than for the urethral pressure. This was in contrast to oxymetazoline and NS-49. The ED50 values for oxymetazoline on urethral pressure, and systolic and diastolic blood pressure were 0.00067, 0.0030 and 0.0020 mg/kg, respectively. The ED50 values for NS-49 on urethral pressure, and systolic and diastolic blood pressure were 0.019, 0.21 and 0.18 mg/kg, respectively. Clonidine and UK 14,304 had no effect on urethral or blood pressure. The oxymetazoline-evoked increase in urethral pressure was inhibited by WB-4101 with an ID50 (dose that gives half of the inhibitory effect) significantly lower than that for rauwolscine.

CONCLUSIONS

The results suggest that in the female rabbit in vivo activation of alpha1-adrenoceptors increased the urethral pressure. Phenylephrine and phenylpropanolamine, in contrast to oxymetazoline and NS-49, selectively enhanced blood pressure as compared with urethral pressure. Provided that the present results also have validity in humans, it would seem possible to develop urethra-selective drugs for treatment of stress incontinence with few or no cardiovascular side-effects.

[Oral therapy of erectile dysfunction]

Erectile disfunction (E. D.) is more common in older men but may affect younger men too. Diabetes mellitus, coronary heart disease and hypertension are often associated with E. D. The majority of the patients are treated medically for erectile dysfunction and, recently, oral therapy has become most important since Viagra has been approved. New phosphodiesterase blockers are in preclinical evaluation since then. Phentolamine and apomorphine will become available soon for the treatment of E. D. It is important to know about the etiology of E. D. as well as the mechanisms by which drugs may improve erection in order to decide which drug is appropriate for a particular patient.

Yohimbine in erectile dysfunction: the facts

Yohimbine, a pharmacologically well-characterized alpha-2-adrenoceptor antagonist with activity in the central and peripheral nervous system, has been used for over a century in the treatment of erectile dysfunction. In-depth, systematic studies in animals have shown that the drug has a remarkable positive effect on sexual performance. Meta-analyses of the few controlled, randomized human studies have consistently shown an advantage of yohimbine over placebo. Despite such a long history and encouraging activity, the drug has not yet been subjected to scientifically rigorous human clinical trials. Although relevant basic pharmacological and animal research information has been available for over 15 y, recent studies were designed with a lack of insight and complete disregard of those fundamental studies. Currently, dose-response investigations are not available, alternative routes of administration (i.e. sublingual) have not been investigated, nor has continuous versus 'on-demand' administration been explored. Synergistic activity with other drugs was last studied nearly four decades ago. Assessment of various populations was carried out in very limited cohorts and only in most general terms. In short, properly designed trials in humans have not been done. Why? Yohimbine is an old drug. As such it does not enjoy patent protection or commercial viability. Until molecular/formulation changes can be brought about (as recently happened with two other agents: phentolamine and apomorphine), serious investigations of yohimbine will remain in limbo. It could be that the nay sayers are right and yohimbine, indeed, lacks clinical activity as a treatment for men with erectile dysfunction. As long as it remains an orphan drug, we will never know.

[Pharmacotherapy of erectile dysfunction]

Among the drugs used to treat erectile dysfunction most common are prostaglandins El, viagra, iochimbin, vasodilators and desaggregants, vitamins, biogenic stimulators, etc. The comparative analysis of their efficacy was made in 360 patients with erectile dysfunction, primarily at subcompensated stage, aged 17-83 years. Organic and psychogenic erectile dysfunctions were diagnosed in 69 and 31% of the patients, respectively. Intracavernous injections of prostaglandin El (Caverject) were effective in 74%, transurethral alprostadil (MUSE) when adjusting the dose--in 38.7% of the patients. Iochimbin in patients with organic and psychogenic forms of erectile dysfunctions was effective in 25 and 40% of patients, respectively. In 26.3 and 19% of such patients the response was obtained after use of the combination including xantinol, nicotinate, trental, biogenic stimulators and adaptogens. Viagra was effective in 60 and 77.3% of patients with psychogenic and organic erectile dysfunctions, respectively.

Alpha-adrenergic blockade in preventing posttransplant edema of lung allograft

Effect of alpha-adrenergic blockers on pulmonary edema in lung transplantation was studied with a rat model of syngeneic left lung transplantation. Prior to harvesting, 0.1 mg of Prazosin or 0.4 mg of Yohimbine was given to the donor. Pulmonary and systemic hemodynamics were measured under the right pulmonary arterial occlusion (RPAO) at different time points after grafting. Wet to dry weight ratio (W/D) of all transplants was also calculated. Same procedure was conducted in rats with normal and ischemic lung and in transplanted animals without any treatments. While RPAO did not increase W/D in normal lung with a significant elevation in pulmonary arterial pressure (PAP), both these values significantly increased in transplanted lung. Transplanted animals could not tolerate RPAO 24 hours after grafting, but were tolerable later than 48 hours with elevated W/D and PAP. On the contrary, animals given Prazosin or Yohimbine were all tolerable at 24 hours postsurgery. Yohimbine significantly improved W/D. Consequently, it was demonstrated that pulmonary edema of the graft reached its peak during first 24 to 48 hours after transplantation and was alleviated by the blockade of alpha-adrenergic receptor in the graft vessel.