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PubMedDate not supplied

The reversal of the ischemic effects of epinephrine on a finger with local injections of phentolamine.

The use of phentolamine (Regitine) as a specific competitive antagonist of epinephrine by virtue of its alpha-blocking properties is well known. Its use via digital nerve block infiltration has been described in cases of IV infiltration of sympathomimetics. We discuss a recent case of local and direct infiltration of phentolamine along the course of the digital arteries and directly into the thumb tuft to reverse the local ischemic effects of epinephrine.

Adult↗

PubMed1976

The effect of simultaneous administration of levarterenol and phentolamine on renal blood flow.

The effect of simultaneous administration of levarterenol and phentolamine upon renal blood flow was studied over a 3-hour period in 22 mongrel dogs. The infusion of levarterenol alone produced a fall in renal blood flow that ranged from 28 to 58% from the baseline value. When both drugs were administered simultaneously, renal flow fell only 17 to 22% from baseline (p less than 0.05). From these studies we conclude that the simultaneous administration of levarterenol and phentolamine in optimal ratios maintains renal blood flow near baseline levels.

Animals↗

PubMed2001

Unexpected and pronounced antinociceptive synergy between spinal acetaminophen (paracetamol) and phentolamine.

Acetaminophen was administered to mice by spinal (intrathecal, i.t.) injection alone or with phentolamine (11.3 microg = 0.03 micromol). Acetaminophen produced dose-related antinociception in the abdominal irritant test with an ED(50) value of 137.2 microg (0.9 micromol) Phentolamine had no effect. For combined administration, the potency of acetaminophen was significantly increased (ED50=24.4 vs. 137.2 microg), indicative of multiplicative interaction and strong synergism. These results reveal the significant and surprising interaction of spinal cord adrenoceptors or ion channel subtypes with acetaminophen-induced antinociception.

Acetaminophen↗

PubMed1992

Intracavernous self-injection with vasoactive intestinal polypeptide and phentolamine in the management of erectile failure.

A total of 52 men, median age 55 years (range 28 to 74 years), with erectile failure was treated with vasoactive intestinal polypeptide and phentolamine. Impotence was classified as psychogenic in 3 patients, psychogenic/arteriogenic in 3, arteriogenic in 25, arteriogenic/neurogenic in 4, neurogenic in 5, venous leakage/psychogenic in 2, venous leakage/neurogenic in 1 and following venous leak surgery in 9. The patients were treated with 30 micrograms vasoactive intestinal polypeptide and 0.5 to 2.0 mg. phentolamine. A total of 1,380 self-injections was given and the number of injections per patient varied from 5 to 245. No patient had priapism, corporeal fibrosis or other serious complications. After sexual stimulation all patients obtained erection sufficient for penetration. Following ejaculation rigidity decreased normally. The median duration of treatment was 6 months (range 1 to 22). Nine patients discontinued treatment. One patient with severe arteriosclerosis experienced decreased effectiveness of the drug and received a penile prosthesis. Five patients elected not to perform self-injection any longer, 1 psychogenic impotent patient was cured, and 1 patient discontinued therapy due to palpitation and sweating. One patient died of a myocardial infarction not associated with this therapy.

Adult↗

PubMed1989

Treatment of impotence by intrapenile injections. A comparison of papaverine versus papaverine and phentolamine: a double-blind, crossover trial.

The efficacy of papaverine, and a combination of papaverine and phentolamine as a pharmacological treatment of impotence was compared in a double-blind, crossover trial. A total of 40 impotent men received intracavernous injections of papaverine (40 mg.) or a combination of papaverine (20 mg.) and phentolamine (0.5 mg.) at monthly intervals. Observations at 20 minutes after injection demonstrated that papaverine caused full erections in 27 per cent of the men and partial erections in 65 per cent. The combined injection resulted in full erections in 48 per cent of the men and 52 per cent had partial erections. The difference was significant (Z equals 2.29, p less than 0.05).

Adult↗

PubMed1988

Physicochemical stability of papaverine hydrochloride-phentolamine mesylate mixtures used for intracavernous injection: a preliminary evaluation.

Physicochemical stability of intracavernous injections of 30 mg. per ml. papaverine hydrochloride with 0.5 or 1.0 mg. per ml. phentolamine mesylate used to induce erection in patients with impotence was examined. The samples were stored at room temperature, in the refrigerator at 4C and in the freezer at -20C for 6 months. The examination consisted of visual observation for change in color or evidence of precipitation, measurement of pH and thin layer chromatography at different intervals. During the 6 months of storage no change had occurred in pH, color development, precipitation or formation of new moieties. Therefore, the aforementioned injection solutions of papaverine hydrochloride with phentolamine mesylate can be dispensed safely with instruction to patients for adequate storage and manipulation.

Drug Combinations↗

PubMed1988

Erectile responses to intracavernous papaverine and phentolamine: comparison of single and combined delivery.

In a prospective study of 15 consecutive impotent patients we evaluated the erectile responses to intracavernous injections of standardized doses of papaverine and phentolamine alone and in combination. Of the 15 patients 13 achieved a full erection with the drug combination, whereas only 6 achieved a full erection with papaverine and 1 with phentolamine. Our results suggest an effective alternative to the use of papaverine alone, whose long-term sequelae have been shown to be deleterious.

Adult↗

PubMed2001

Differential antinociceptive effect of transcutaneous electrical stimulation on pain behavior sensitive or insensitive to phentolamine in neuropathic rats.

The effects of transcutaneous electrical stimulation and systemic injection of phentolamine, a non-specific alpha-adrenergic antagonist, on the behavioral signs of mechanical allodynia and cold hyperalgesia in rats with nerve injury were investigated. Mechanical allodynia and cold hyperalgesia were evaluated by measuring the paw withdrawal frequency (PWF) resulting from repetitive application of a von Frey hair and the paw lift duration (PLD) at a cold temperature, respectively. After a unilateral nerve injury, both PWF and PLD increased in the injured hind paw. Application of low-frequency, high-intensity transcutaneous electrical stimulation (LFHI-TES) to the injured hind paw depressed the injury-induced increased PWF, whereas it had no effect on the injury-induced increased PLD. Naloxone reversed the LFHI-TES produced depression of PWF. Intraperitoneal administration of phentolamine depressed the injury-induced increased PLD without affecting the injury-induced increased PWF. Our results suggest that LFHI-TES, which activates the endogenous opioid systems, produces an antinociceptive effect that appears to be related to whether or not the pain is mediated by sympathetic activity.

Adrenergic alpha-Antagonists↗

PubMed1981

Determination of the major metabolite of phentolamine in human plasma and urine by high-performance liquid chromatography.

A reversed-phase, high-performance liquid chromatographic method using UV detection is described for the assay of the major metabolite of phentolamine in plasma and urine before or after enzymatic hydrolysis. Plasma is deproteinized with methanol. The sensitivity limit is 200 ng/ml using 150-microliters samples. Urine is either diluted with water or purified after enzymatic hydrolysis. Concentrations down to 2--3 micrograms/ml could be quantified with acceptable precision. This method was applied to plasma and urine samples from subjects given phentolamine.

Arylsulfatases↗

PubMed2002

Combination therapy for erectile dysfunction: a randomized, double blind, unblinded active-controlled, cross-over study of the pharmacodynamics and safety of combined oral formulations of apomorphine hydrochloride, phentolamine mesylate and papaverine hydrochloride in men with moderate to severe erectile dysfunction.

Oral therapy has become first line treatment for patients with mild to moderate erectile dysfunction (ED). Studies have shown that sildenafil may not be effective in all patients, and has been associated with a variety of adverse effects and an adverse interaction with nitrates and inhibitors of cytochrome P450 enzymes. The objective was to compare the efficacy and safety of three different oral combinations with the highest dose of sildenafil in men with moderate to severe ED. Randomized, double blind, unblinded active-controlled, Phase II study was carried out at three sites in Mexico. After a 4-week placebo run-in period, patients received all four of the following treatments using a 4-way cross-over design: 40 mg phentolamine (PM) +6 mg apomorphine (Apo); 40 mg PM +150 mg papaverine (Pap); 40 mg PM +6 mg Apo +150 mg Pap (Tricombo); 100 mg sildenafil (SC). With the exception of sildenafil tablets, all study medication was blinded. Moderate to severe ED was defined as a less than 50% vaginal penetration success rate during the placebo run-in period. A total of 44 patients were enrolled, of whom 36 completed all four treatment periods. All treatments produced a significant effect in primary efficacy variable (Sexual Encounter Profile) compared to baseline, however, no statistically significant differences were found between treatments. A significant period effect was observed. Also, the four treatments were found not to differ significantly in five out of six secondary efficacy variables. The lowest incidence of treatment-related adverse events (AE) occurred in the 40 mg PM +6 mg Apo group (9.8%), followed by 100 mg SC (15%), and the other two combinations (16.7 and 17.5%, respectively). Nasocongestion and headache were the most frequently reported AE. An oral combination of vasoactive agents may provide an alternative approach to sildenafil. Based on these results a combination of phentolamine and apomorphine warrants further clinical investigation.

Adrenergic alpha-Antagonists↗

PubMedDate not supplied

Phentolamine use in a neonate for the prevention of dermal necrosis caused by dopamine: a case report.

Skin ischemia, necrosis, and gangrene are uncommon but known complications of dopamine extravasation. In most cases, these complications are associated with the use of high-dosage dopamine infusion. Subcutaneous phentolamine has been used as a therapeutic agent for these complications. However, this is the report of the first neonatal case report in the English literature of prompt reversal of imminent dermal ischemia and necrosis associated with low-dose dopamine infusion using subcutaneous phentolamine.

Dopamine↗

PubMed1996

Phentolamine precludes inhibitory effect of the K+ channel opener pinacidil on insulin release.

The K+ channel opener pinacidil, in clinical use as an antihypertensive agent, acts by opening ATP-sensitive K+ channels in striated and smooth muscle cells. In vitro and in vivo studies have suggested that it also diminishes insulin secretion. Insulin secretion can be influenced directly--by acting on the ATP-sensitive K+ channels of the pancreas--or indirectly--by activation of the sympathetic nervous system, caused by vasodilation. Therefore we studied the effect of pinacidil on insulin release after intravenous glucose challenge during alpha-adrenergic blockade with phentolamine. We found, that phentolamine precludes the effect of pinacidil on glucose induced insulin release in healthy man. This finding suggests that the inhibitory effect of pinacidil on insulin release is indirect and due to activation of the sympathetic nervous system. The latter effect is caused by the antihypertensive action of pinacidil. However, the suggestion of others, that pinacidil inhibits insulin secretion secretion via a direct action on ATP-sensitive K+ channels can not be excluded.

Adrenergic alpha-Antagonists↗

PubMed1976

Hemorrhagic necrosis of pheochromocytoma associated with phentolamine administration.

A case of ruptured pheochromocytoma is presented, the pathophysiology discussed, and the literature reviewed. Evidence is presented that the use of alpha-adrenergic blockade in general, and phentolamine in particular, may predispose to this complication. Twelve cases of massive hemorrhagic necrosis with or without rupture were found in the literature, including the present case. Six had no operation; one survived. Six had immediate operation; 4 survived. An additional case of hemorrhage into a small pheochromocytoma following phentolamine is presented. This tumor was neither ruptured nor massively necrotic, but the case supports the hypothesis that alpha-adrenergic blockade may cause hemorrhage within the pheochromocytoma.

Adrenal Gland Neoplasms↗

PubMedDate not supplied

Effects of prazosin and phentolamine on arterial pressure, heart rate, and renin activity: evidence in the conscious rat for the functional significance of the presynaptic alpha-receptor.

We examined the functional significance of the presynaptic alpha-adrenergic receptor, to stimulus-induced norepinephrine release. The effects of prazosin and phentolamine, alpha-adrenergic receptor antagonists with different in vitro selectivities for the presynaptic alpha-receptor, on mean arterial pressure and serum renin activity were determined in the conscious rat. Both drugs resulted in dose-related reductions in mean arterial pressure and dose-related increase in heart rate and serum renin activity. However, consistent with the greater selectivity of prazosin for the postsynaptic alpha-receptor, a given reduction in arterial pressure was associated with a lesser increment in heart rate and serum renin activity after prazosin than after the nonselective agent phentolamine. The differential effects of these agents on heart rate and serum renin activity are consistent with different degrees of blockade of a functionally significant presynaptic alpha-receptor.

Animals↗

PubMed1988

Effects of intrathecal administration of methysergide, phentolamine, and pindolol on pressor responses to electrical stimulation of the rostral ventrolateral medulla.

Neurons projecting from the rostral ventrolateral medulla (RVLM) to the spinal cord are important in blood pressure control. The present experiments examined the role of spinal adrenoreceptors and serotonin receptors in mediating the pressor effects of electrical stimulation of the RVLM. Accordingly the effects on blood pressure of electrical stimulation of the RVLM were studied before and after intrathecal administration of adrenergic or serotonergic antagonists in normotensive and hypertensive rats. Electrical stimulation in the area of the RVLM-B3 serotonin-containing neurons in Wistar-Kyoto (WKY) rats increased blood pressure, and the pressor responses were reduced by intrathecal methysergide (30 and 100 micrograms). Similar findings were seen in spontaneously hypertensive rats (SHR). In WKY, electrical stimulation in the area of the RVLM-C1 epinephrine-containing neurons, increased mean arterial pressure (MAP), but the pressor responses were unaffected by intrathecal phentolamine (15 micrograms), pindolol (2 micrograms), or methysergide (30 and 100 micrograms), or saline. The results suggest that the pressor effects of stimulation of the RVLM-B3 area are mediated at least in part through activation of spinal serotonin receptors. The lack of effect of phentolamine and pindolol on the RVLM-C1 area pressor responses raises a question regarding the importance of spinal adrenergic receptors in mediating these effects.

Animals↗

PubMed1997

Effects of phentolamine or yohimbine on naloxone's actions during endotoxin shock in rats.

Endogenous opioids are known to mediate some of the cardiovascular sequelae of sepsis. Inhibition of adrenergic action has been implicated as a physiological path by which endogenous opioids cause deleterious changes in cardiovascular function during endotoxin shock, but where and to what extent this accounts for changes in regional vascular resistance remains unclear. In this study, we addressed this question by examining the role of alpha-adrenergic actions in cardiovascular performance and the regional perfusion changes caused by naloxone during endotoxin shock. Rats had catheters inserted into the tail artery, left cardiac ventricle, and jugular vein. Twenty-four hours later, rats received saline or endotoxin (2 mg/kg) challenge intravenously over 30 min, followed at 40 min by intravenous naloxone (or saline) treatment (4 mg/kg + 2 mg/kg x h) in the presence or absence of phentolamine (100 micrograms/kg + 600 micrograms/kg x h) or yohimbine (40 micrograms/kg + 4 micrograms/kg x h). Radiolabeled microspheres were used to determine cardiac outputs and blood flows at 0, 30, 60, and 120 min after beginning endotoxin infusion. Naloxone attenuated the endotoxin-induced decline in mean arterial pressure (MAP) and cardiac output (CO), but had no effect on increased systemic vascular resistance (SVR). Phentolamine blocked naloxone's ability to increase MAP and CO, but permitted an increase in SVR by naloxone. In the presence of yohimbine, naloxone still increased MAP, but not CO nor SVR. Regional vascular responses varied, with naloxone demonstrating a vasoconstrictive effect despite alpha-adrenergic receptor blockade in some beds, and no effect in others. The response of individual organs in the hepatosplanchnic circulation was heterogenous as well. These data suggest that some effects of endogenous opioids during endotoxin shock are mediated via inhibition of alpha-adrenergic effects, but that some cardiovascular effects of endogenous opioids are independent of adrenergic control during endotoxin shock.

Adrenergic alpha-Antagonists↗

PubMed1987

Comparison of nasal responsiveness to histamine, methacholine and phentolamine in allergic rhinitis patients and controls.

In a selected group of rhinitis patients with an IgE-mediated allergy to house dust mites the nasal response to insufflation of histamine chloride, methacholine and phentolamine was demonstrated to be higher than in a control group. With the methods used histamine chloride was better at discriminating between healthy subjects and patients than methacholine or phentolamine. This discrimination was shown by assessing the severity of reflex-mediated symptoms such as the number of sneezes and the amount of secretion, and not by differences in nasal airway resistance.

Adult↗

PubMed1991

Nasal hyper-responsiveness to histamine, methacholine and phentolamine in patients with perennial non-allergic rhinitis and in patients with infectious rhinitis.

Recently it has been shown that patients with atopic rhinitis and with an allergy to house dust mites have a stronger nasal response to insufflation of histamine, methacholine and phentolamine than a control group. This hyper-responsiveness could not be demonstrated in patients with perennial non-allergic rhinitis, unless the patients were selected according to the predominant symptoms in the history. Patients with rhinorrhoea ('runners') proved to be hyper-responsive to methacholine compared with normal controls. The existence of two subpopulations was emphasized by hyper-responsiveness to both histamine and methacholine in the runners group compared with the patients with a stuffy nose ('blockers'). Patients with chronic nasal infections (characterized by recurrent episodes of purulent discharge) showed no hyper-responsiveness at all, indicating that either hyper-reactivity does not play an important part in this patient population or methods to detect hyper-reactivity in this group are inadequate. In contrast to our earlier observations in patients with atopic rhinitis, increased responsiveness to phentolamine could not be detected either in the patients with perennial rhinitis or in the patients with infectious rhinitis, indicating that the possible alpha-adrenergic dysfunction found in patients with atopic rhinitis is restricted to this group.

Adolescent↗