Treatment of essential hypertension with a new vasodilator in combination with beta-adrenergic blockade

Minoxidil-Related Pericarditis

This paper reports a case of a 53-year-old man presenting with recurrent pericardial effusions and one episode of pericarditis after short-term, low-dose minoxidil use, without prior kidney or heart failure history. The uniqueness lies in the rapid onset of a moderate pericardial effusion within 20 days, notably shorter than previously documented.

Minoxidil-associated pericardial effusion and impending tamponade

ABSTRACT

A patient with a large pericardial effusion and impending tamponade exhibited clinical improvement with urgent pericardiocentesis. Further workup ruled minoxidil to be the likely cause of the effusion. After discontinuation of minoxidil, the effusion did not recur.

There Is a Positive Dose-Dependent Association between Low-Dose Oral Minoxidil and Its Efficacy for Androgenetic Alopecia: Findings from a Systematic Review with Meta-Regression Analyses

Background

Recently, low-dose oral minoxidil (LDOM) has entered the landscape of therapies for androgenetic alopecia (AGA). We determined whether using LDOM is associated with improving AGA in a dose-dependent manner; secondarily, we examined whether a dose-dependent association also exists for safety.

Methods

Systematic searches were conducted in PubMed and Scopus to identify studies that would be eligible for our quantitative analyses; the logistics of our analyses was determined by the data we gathered.

Results

Six studies were eligible for quantitative analyses; we conducted meta-regressions. We found that, for persons with AGA, increasing the dosage of LDOM by 1 mg/day was − after six months − significantly associated with an expected sex-adjusted increase in hair diameter (mean difference = 1.4 μm, p = 0.01), total hair density (mean difference = 47.1 hairs/cm², p = 0.007), terminal hair density (mean difference = 9.1 hairs/cm², p = 0.001), risk of hypertrichosis (mean difference = 17.9%, p = 0.006), and cardiovascular adverse events (mean difference = 4.8%, p = 0.004).

Conclusions

Our study produced new evidence as our work is the first to show a positive dose-dependent association between the use of LDOM and change in hair diameter, hair density, risk of hypertrichosis, and cardiovascular adverse events for persons with AGA. Future randomized trials could produce causal evidence that would corroborate these dose-dependent associations.

Minoxidil: a comprehensive review

Topical minoxidil (5% foam, 5% solution, and 2% solution) is FDA-approved for androgenetic alopecia (AGA) in men and women.Mechanism of action: Minoxidil acts through multiple pathways (vasodilator, anti-inflammatory agent, inducer of the Wnt/β-catenin signaling pathway, an antiandrogen), and may also affect the length of the anagen and telogen phases.Pharmacokinetics: Approximately 1.4% of topical minoxidil is absorbed through the skin. Minoxidil is a prodrug that is metabolized by follicular sulfotransferase to minoxidil sulfate (active form). Those with higher sulfotransferase activity may respond better than patients with lower sulfotransferase activity.Clinical efficacy (topical minoxidil): In a five-year study, 2% minoxidil exhibited peak hair growth in males at year one with a decline in subsequent years. Topical minoxidil causes hair regrowth in both frontotemporal and vertex areas. The 5% solution and foam were not significantly different in efficacy from the 2% solution.Oral and Sublingual minoxidil (not FDA approved; off-label): After 6 months of administration, minoxidil 5 mg/day was significantly more effective than topical 5% and 2% in male AGA. Low-dose 0.5-5 mg/day may also be safe and effective for female pattern hair loss and chronic telogen effluvium. Sublingual minoxidil may be safe and effective in male and female pattern hair loss.

Safety of low-dose oral minoxidil for hair loss: A multicenter study of 1404 patients

BACKGROUND

The major concern regarding the use of low-dose oral minoxidil (LDOM) for the treatment of hair loss is the potential risk of systemic adverse effects.

OBJECTIVE

To describe the safety of LDOM for the treatment of hair loss in a large cohort of patients.

METHODS

Retrospective multicenter study of patients treated with LDOM for at least 3 months for any type of alopecia.

RESULTS

A total of 1404 patients (943 women [67.2%] and 461 men [32.8%]) with a mean age of 43 years (range 8-86) were included. The dose of LDOM was titrated in 1065 patients, allowing the analysis of 2469 different cases. The most frequent adverse effect was hypertrichosis (15.1%), which led to treatment withdrawal in 14 patients (0.5%). Systemic adverse effects included lightheadedness (1.7%), fluid retention (1.3%), tachycardia (0.9%), headache (0.4%), periorbital edema (0.3%), and insomnia (0.2%), leading to drug discontinuation in 29 patients (1.2%). No life-threatening adverse effects were observed.

LIMITATIONS

Retrospective design and lack of a control group.

CONCLUSION

LDOM has a good safety profile as a treatment for hair loss. Systemic adverse effects were infrequent and only 1.7% of patients discontinued treatment owing to adverse effects.

Efficacy and Safety of Oral Minoxidil 5 mg Once Daily in the Treatment of Male Patients with Androgenetic Alopecia: An Open-Label and Global Photographic Assessment

Introduction

Oral minoxidil is an antihypertensive vasodilator known to stimulate hair growth. The use of low-dose oral minoxidil for the treatment of male androgenetic alopecia (AGA) is receiving increasing attention. The aim of this study was to evaluate the efficacy and safety of oral minoxidil for the treatment of male AGA.

Methods

This was an open-label, prospective, single-arm study. Thirty men aged 24–59 years with AGA types III vertex to V were treated with oral minoxidil 5 mg once daily for 24 weeks. Efficacy was evaluated by hair counts, hair diameter measurements, photographic assessment, and self-administered questionnaire. The safety of the treatment was closely monitored by means of physical examinations and laboratory investigations.

Results

There was a significant increase in total hair counts from baseline at weeks 12 (mean change + 26, range 182.5–208.5 hairs/cm²) and 24 (mean change + 35.1, range 182.5–217.6 hairs/cm²) (both p = 0.007). Photographic assessment of the vertex area by an expert panel revealed 100% improvement (score > + 1), with 43% of patients showing excellent improvement (score + 3, 71–100% increase). The frontal area also showed a significant response but less than that of the vertex area. Common side effects were hypertrichosis (93% of patients) and pedal edema (10%). No serious cardiovascular adverse events and abnormal laboratory findings were observed.

Conclusion

Oral minoxidil 5 mg once daily effectively increased hair growth in our male patients with AGA and had a good safety profile in healthy subjects. However, oral minoxidil should be used carefully with men who have severe hypertension and increased risk for cardiovascular events.

Electronic supplementary material

The online version of this article (10.1007/s13555-020-00448-x) contains supplementary material, which is available to authorized users.

Oral minoxidil treatment for hair loss: A review of efficacy and safety

BACKGROUND

Although topical minoxidil is an effective treatment option for hair loss, many patients are poorly compliant because of the necessity to apply the medication twice a day, undesirable hair texture, and scalp irritation.

OBJECTIVE

In recent years, oral minoxidil at low dose has been proposed as a safe alternative. This study reviewed articles in which oral minoxidil was used to treat hair loss to determine its efficacy and safety as an alternative to topical minoxidil.

METHODS

PubMed searches were performed to identify articles discussing oral minoxidil as the primary form of treatment for hair loss published up to April 2020.

RESULTS

A total of 17 studies with 634 patients were found discussing the use of oral minoxidil as the primary treatment modality for hair loss. Androgenetic alopecia was the most studied condition, but other conditions included telogen effluvium, lichen planopilaris, loose anagen hair syndrome, monilethrix, alopecia areata, and permanent chemotherapy-induced alopecia.

LIMITATIONS

Larger randomized studies comparing the efficacy/safety of different doses with standardized objective measurements will be needed to clarify the best treatment protocol.

CONCLUSION

Oral minoxidil was found to be an effective and well-tolerated treatment alternative for healthy patients having difficulty with topical formulations.

Off-Label Use of Topical Minoxidil in Alopecia: A Review

Topical minoxidil is a well-known and often-utilized drug in dermatological practice for the treatment of alopecia. It was approved by the United States Food and Drug Administration for the treatment of androgenetic alopecia in 1988. Since its approval, minoxidil has been used off-label for the treatment of many other types of alopecia, with minimal formal evidence of efficacy. Conditions for which the use of topical minoxidil has been reported include telogen effluvium, alopecia areata (AA), scarring alopecia, eyebrow hypotrichosis, monilethrix, and chemotherapy-induced alopecia (CIA). The evidence for the use of minoxidil in each condition is derived from a variety of studies, including clinical trials, case series, and case reports. A comprehensive review of the literature indicates that while minoxidil is routinely used in the management of many alopecic conditions, there is mixed evidence for its efficacy. For certain conditions, including AA and most scarring alopecias, the evidence seems to be inconclusive. For others, such as eyebrow hypotrichosis, monilethrix, early traction alopecia, and CIA, there is more support for the efficacy of minoxidil. Although the favorable safety profile of minoxidil is established in adults, its use in the treatment of pediatric alopecia may require heightened monitoring and patient education.

Perivascular adipose tissue and the dynamic regulation of Kv 7 and Kir channels: Implications for resistant hypertension

Resistant hypertension is defined as high blood pressure that remains uncontrolled despite treatment with at least three antihypertensive drugs at adequate doses. Resistant hypertension is an increasingly common clinical problem in older age, obesity, diabetes, sleep apnea, and chronic kidney disease. Although the direct vasodilator minoxidil was introduced in the early 1970s, only recently has this drug been shown to be particularly effective in a subgroup of patients with treatment-resistant or uncontrolled hypertension. This pharmacological approach is interesting from a mechanistic perspective as minoxidil is the only clinically used K⁺ channel opener today, which targets a subclass of K⁺ channels, namely K_ATP channels in VSMCs. Beside K_ATP channels, two other classes of VSMC K⁺ channels could represent novel effective targets for treatment of resistant hypertension, namely K_v 7 (KCNQ) and inward rectifier potassium (K_ir 2.1) channels. Interestingly, these channels are unique among VSMC potassium channels. First, both have been implicated in the control of microvascular tone by perivascular adipose tissue. Second, they exhibit biophysical properties strongly controlled and regulated by membrane voltage, but not intracellular calcium. This review focuses on K_v 7 (K_v 7.1-5) and K_ir (K_ir 2.1) channels in VSMCs as potential novel drug targets for treatment of resistant hypertension, particularly in comorbid conditions such as obesity and metabolic syndrome.

Antihypertensive drugs

Successful treatment of hypertension is possible with limited side effects given the availability of multiple antihypertensive drug classes. This review describes the various pharmacological classes of antihypertensive drugs, under two major aspects: their mechanisms of action and side effects. The mechanism of action is analysed through a pharmacological approach, i.e. the molecular receptor targets, the various sites along the arterial system, and the extra-arterial sites of action, in order to better understand in which type of hypertension a given pharmacological class of antihypertensive drug is most indicated. In addition, side effects are described and explained through their pharmacological mechanisms, in order to better understand their mechanism of occurrence and in which patients drugs are contra-indicated. This review does not address the effectiveness of monotherapies in large randomized clinical trials and combination therapies, since these are the matters of other articles of the present issue. Five major pharmacological classes of antihypertensive drugs are detailed here: beta-blockers, diuretics, angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists, and calcium channel blockers. Four additional pharmacological classes are described in a shorter manner: renin inhibitors, alpha-adrenergic receptor blockers, centrally acting agents, and direct acting vasodilators.

Minoxidil for Treatment of Resistant Hypertension in Chronic Kidney Disease--A Retrospective Cohort Analysis

Resistant hypertension is still a challenge and reserve antihypertensive agents are often necessary to achieve blood pressure control. One reserve antihypertensive is minoxidil, a direct vasodilator that is known for its strong blood pressure-lowering effect, but contemporary studies are sparse. The authors retrospectively analyzed 54 inpatients with uncontrolled hypertension despite the combined use of current antihypertensive agents. To investigate the effect of minoxidil when added to other antihypertensive agents, blood pressure was evaluated at the time minoxidil treatment was initiated and at discharge. Minoxidil treatment was associated with a significant reduction in blood pressure from 162.4±15.1/83.2±12.7 mm Hg to 135.8±12.2/72.8±6.9 mm Hg (P<.0001). This effect was sustained across all analyzed subgroups. Although the well-known adverse events of minoxidil limit its widespread use, these data show that minoxidil as a reserve antihypertensive agent still has a niche indication in the particular subgroup of patients with treatment-resistant or uncontrolled hypertension.

Hypertension in Pediatrics

Hypertension occurring during childhood and adolescence is being recognized more frequently today than in the past. Hypertension in the pediatric population differs from that in adults with respect to incidence, etiology, clinical presentation, and drug treatment. This article reviews both the pathophysiology and drug treatment of hypertension in pediatric patients. A plan for drug management is presented.

Problems in Predicting Drug Effects across Species Lines

During the course of drug development, there are many instances where extrapolation of data from animals to man is difficult because the toxicologic and metabolic responses induced by drugs may be significantly different between the laboratory species. In cases where the drug in question has a potentially major therapeutic use in man, it is suggested that the data be evaluated on the basis of a pragmatic benefit-to-risk ratio, rather than zero-toxicity. In this way, we may provide drug therapy for those patients for whom adequate treatment does not exist, as well as protect those individuals who may be exposed to some hazard from the use of medicines.

Older blood pressure medications-do they still have a place?

Hypertension is a major risk factor for cardiovascular disease, but control of hypertension remains inadequate, often because of poor patient adherence to prescribed medical regimens that are viewed as poorly tolerated and expensive. Physicians have largely stopped using some older blood pressure medications in favor of newer agents, mostly because of a presumed more favorable side effect profile. The investigators reviewed the pharmacologic properties and the evidence supporting the effectiveness and tolerability of several older blood pressure drugs: sympatholytic agents such as reserpine, methyldopa, and clonidine; diuretics such as chlorthalidone, ethacrynic acid and spironolactone; the vasodilators hydralazine and minoxidil; and others. In conclusion, some of these drugs are well studied and represent alternatives for patients who cannot afford or tolerate newer medications.

Changes in plasma volume and extracellular fluid volume and after addition of hydralazine to propranolol treatment in patients with hypertension

In 16 patients with hypertension, BP could not be controlled satisfactorily by treatment with propranolol alone (mean dosage 325 mg/day). Plasma volume (PV) (T-1824) and extracellular fluid volume (ECV) (82Br-distribution space) were determined in these patients before and after the addition of hydralazine for three months (mean dosage 135 mg/day). After the addition of hydralazine, PV and ECV increased significantly, by 9% and 3%, respectively. Systolic and diastolic BPs decreased, by 15% and 13%. The mechanisms inducing fluid retention during treatment with hydralazine and the clinical significance of the problem are discussed. It is concluded that the addition of a diuretic to propranolol-hydralazine treatment is often well indicated.

Minoxidil in severe hypertension

Minoxidil has been administered to 16 patients with severe hypertension and renal failure. In every patient the indication for minoxidil treatment was resistance to conventional drugs. The final dose of minoxidil was 2.5--30 mg (average 20) and it was combined with a beta-blocking agent and a diuretic (or dialysis). The therapy was given for 1--27 months (average 12). The average supine BP fell from 200/130 to 164/96 mmHg and the upright BP from 200/120 to 152/90 mmHg. No hypotensive reactions occurred. In most patients the progression of hypertensive organ changes was arrested. No major vascular complications have occurred during the 16 years of treatment. Prickling of the skin and hirsutism were common side-effects. The other side-effects observed were oedema in five patients and development of latent diabetes in three. In four patients minoxidil treatment was discontinued for following reasons: successful reconstruction of the renal artery after stenosis, renal transplantation, severe oedema and hirsutism. The risk of hirsutism is a contraindication to prolonged minoxidil administration in most femal patients. Minoxidil is especially indicated in uncontrolled renal hypertension.

The antihypertensive effect of prazosin on mild to moderate hypertension, changes in plasma volume, extracellular volume and glomerular filtration rate

Changes in blood pressure, plasma volume (PV) (125I-albumin space), extracellular volume (ECV) (82Br-space) and glomerular filtration rate (GFR) (51Cr-EDTA clearance) were measured in 12 patients with mild to moderate essential hypertension on placebo and during long-term treatment with prazosin. During the study, BP decreased from an average of 172/107 to 166/102 mmHg (n.s.). PV increased from 3278 to 3324 ml (n.s.) and ECV from 18360 to 18639 ml (n.s.). GFR was almost unchanged, 95 and 93 ml/min, prespectively. An inverse significant correlation was found between the changes in mean BP and changes in ECV, i.e. fluid retention was demonstrated in patients with the smallest BP reduction. It is concluded that inadequate BP response during treatment with prazosin may in part be due to fluid retention. It is therefor suggested that prazosin should in principle be used together with a diuretic in order to prevent fluid retention.

Controlled clinical study on antihypertensive treatment with a diuretic and methyldopa compared with a beta-blocking agent and hydralazine

Twenty-eight previously untreated patients with essential hypertension were included in a randomized double-blind cross-over study comparing the results of treatment with the established combination of a thiazide and methyldopa (regimen A) with the combination of a beta-receptor blocker and hydralazine (regimen B). Three patients each developed intolerable side-effects on each regimen but they were all treated successfully on the alternative regimen. The remaining 22 patients obtained a significant reduction in BP at rest and during exercise on both treatments, with no significant difference between the two schedules. Heart rate was significantly reduced at rest and during exercise with regimen B, while a significant reduction was also obtained following exercise on regimen A. There was no significant difference between the two regimens as to tolerable side-effects during treatment, which were registered in about 60% of the patients on each scheme. However, 64% of the patients were treated satisfactorily without side-effects on either regimen. It is concluded that the combination of a beta-blocking agent and hydralazine is without obvious advantages compared with the combination of thiazide and methyldopa in obtaining initial BP control in patients with essential hypertension.

Minoxidil: an underused vasodilator for resistant or severe hypertension

Minoxidil is a direct vasodilator introduced in the early 1970s for the treatment of hypertension. It is capable of reducing blood pressure in most persons with resistant hypertension where therapy has failed with multidrug regimens. Minoxidil's effect can be limited because of an increase in pulse rate and/or sodium (and water) retention. The latter may prove quite debilitating in some patients. Thus, minoxidil is generally administered with both a diuretic and an agent that can keep pulse rate in check, such as a beta blocker or a combined alpha-beta blocker. The prominent tachycardia with minoxidil can aggravate myocardial ischemia and, if long-standing, leads to left ventricular hypertrophy. Minoxidil has a particularly annoying side effect of hypertrichosis that may limit its use, particularly among women. Minoxidil use is infrequently associated with the idiosyncratic onset of a pericardial effusion. If a patient's hypertension is severe enough to warrant minoxidil therapy, a hypertension specialist should probably become involved in the patient's care. The use of this medication should be limited in view of the availability of effective agents with fewer side effects. There is, however, a place for minoxidil in the treatment of resistant hypertension especially in patients with advanced renal disease.

Topically applied minoxidil may cause fetal malformation: A case report

BACKGROUND

Minoxidil is a K(+) channel opener able to cause relaxation of vascular smooth muscles and modify cell growth and cell fate or migration. It is now widely used for its hair growth promoting effects. When locally applied, it is absorbed through the skin and may have systemic pharmacological effects.

CASE

A 28-year-old white pregnant woman daily applied minoxidil 2% to her scalp because of hair loss. At the 22nd gestational week, after a routine ultrasound test showing significant brain, heart, and vascular malformations of the fetus, pregnancy was interrupted. The placenta had numerous ischemic areas and a discrepancy between gestational age and villi maturation. In the villi, capillaries were increased in number, significantly enlarged, and excessively marginalized. The fetus' heart was increased in volume and had a globose shape, the aorta had a distal stenosis. The sigmoid colon was significantly increased in length and a mesentery commune was present. The brain had enlarged ventricles and abundant hemorrhages. Histological examination showed areas of demyelinization with gliosis, signs of excessive and inappropriate angiogenesis, and capillary rearrangement.

CONCLUSIONS

Further knowledge on minoxidil-induced fetal toxicity would be beneficial before allowing its use in pregnant women.

Direct vasodilators and their role in hypertension management: minoxidil

Minoxidil is a direct vasodilator that has been in use for over two decades. It is used primarily to reduce blood pressure in hypertensives who have been poorly controlled on various multidrug regimens. Although minoxidil is extremely effective, its usefulness is limited by its tendency to increase the pulse rate and to trigger salt and water retention. The latter may be incapacitating in some patients. Therefore, minoxidil is typically administered with both a diuretic and an agent that can control the pulse rate, such as a beta blocker. Minoxidil has several other side effects that may limit its use, including hypertrichosis, aggravation of myocardial ischemia and/or left ventricular hypertrophy, and (infrequently) pericardial effusions. If a patient's hypertensive pattern is sufficiently severe to warrant contemplation of minoxidil therapy, referring the patient to a hypertension specialist should be strongly considered. (c) 2001 by LeJacq Communications, Inc.

Minoxidil inhibits proliferation and migration of cultured vascular smooth muscle cells and neointimal formation after balloon catheter injury

The goal of the study was to investigate the in vitro and in vivo inhibition of minoxidil on smooth muscle cell (SMC) proliferation and migration as well as neointimal formation. The in vitro effect of minoxidil was investigated by Boyden chamber assay and cell-cycle analysis. To evaluate the in vivo effect, we treated the animals with minoxidil in their drinking water before and after balloon catheter injury to carotid artery. Results showed that minoxidil inhibited SMC migration across type I collagen membrane in a dose-related manner (13.5% by 0.01 mg/ml; p < 0.05; 16.8% by 0.05 mg/ml: p < 0.01; 40.4% by 0.25 mg/ml; p < 0.001; and 65.8% by 1.25 mg/ml; p < 0.001). Minoxidil (0.8 mg/ml) increased the number of SMCs in G1 phase (p < 0.05) and decreased the number of SMCs in S phase (p < 0.001). In vivo minoxidil treatment reduced neointimal mass by 31.7% (120 mg/L) and 42.3% (200 mg/L), respectively. Data demonstrate that minoxidil inhibits vascular SMC proliferation and migration both in vitro and in vivo, and therefore may be useful to inhibit SMC hyperplasia that occurs in restenosis and other vascular diseases.

Antihypertensive activity of a nonpeptide angiotensin II receptor antagonist, YM358, in rats and dogs

The antihypertensive activity of YM358, 2,7-diethyl-5-[[2'-(1 H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H-pyrazolo[1,5-b][1,2,4]tri azole potassium salt monohydrate, a new nonpeptide angiotensin II receptor antagonist, was characterized in rats and dogs. In conscious rats, YM358 after a single oral administration (1-30 mg/kg) lowered blood pressure. The rank order of hypotensive potency of YM358 in conscious rats was 2-kidney, 1-clip renal hypertensive rats > spontaneously hypertensive rats > normotensive rats on the basis of maximum hypotension. YM358 also caused decreases in blood pressure in 2-kidney, 1-clip renal hypertensive dogs and furosemide-treated dogs. Repeated administration of YM358 to 2-kidney, 1-clip renal hypertensive rats for 28 days produced a stable and long-lasting antihypertensive effect without influencing circadian blood pressure and heart rate rhythms. No reflex tachycardia was observed in any animals of either species treated with YM358. Therefore, the pharmacological profile of this compound indicates that YM358 has potential as a useful antihypertensive agent.

Coadministration of glyburide and minoxidil, drugs with opposing effects on potassium channels

INTRODUCTION

Adenosine triphosphate (ATP)-sensitive potassium (K+) channels are modulated by drugs, so that they are opened by vasodilators such as minoxidil but are closed by hypoglycemic agents such as glyburide (glibenclamide). Animal studies and in vitro evidence suggests that the coadministration of drugs with opposing effects on K+ channels attenuates their pharmacodynamic effects.

METHODS

To investigate whether this important pharmacodynamic interaction occurs in humans, we administered 5 mg minoxidil, 2.5 mg glyburide or both in a double-blind fashion to nine healthy subjects. Glucose and insulin responses during an intravenous glucose tolerance test (0.3 gm/kg) were measured and blood pressure was recorded for 8 hours. In an additional four subjects the effect of 5 mg glyburide on the hypotensive effect of 5 mg minoxidil was examined.

RESULTS

None of the parameters of glucose metabolism differed significantly when subjects received glyburide alone, minoxidil alone, or glyburide with minoxidil. Minoxidil or minoxidil in combination with 2.5 mg glyburide resulted in a similar significant decrease in blood pressure compared with the response to glyburide alone. The hypotensive effect of minoxidil was smaller in the four subjects who received the higher dose of glyburide, but significant hypoglycemia (blood glucose concentration < 60 mg/dl) occurred in three of the four subjects.

CONCLUSION

We conclude that, in healthy volunteers, the coadministration of 2.5 mg glyburide and 5 mg minoxidil does not result in attenuation of the blood pressure-lowering effect of minoxidil. The smaller hypotensive response in four subjects who received 5 mg glyburide and 5 mg minoxidil suggests the possibility of a dose-related drug interaction. Studies with strict clamping of blood glucose concentrations will be required to address this possibility.

Development of hypertension in animals with reduced total peripheral resistance

The object of the present study was to determine whether deoxycorticosterone acetate (DOCA)-salt hypertension can be produced in rats in the presence of low total peripheral resistance (TPR) induced by long-term administration of minoxidil, a vasodilator. The rats were divided into four groups: sham-control, DOCA-salt, minoxidil, and DOCA-salt with minoxidil. The rats in both DOCA groups had DOCA pellets implanted subcutaneously and were given saline to drink. The rats in both minoxidil groups were given minoxidil (3 mg/day) in the drinking water throughout the experiment. Final measurements, including mean arterial blood pressure, cardiac index, and renal blood flow were made after 4-6 weeks. Flow measurements were made using radioactive microspheres. Cardiac index (ml.min-1.100 g-1) in sham-control rats averaged 18 +/- 2 and was higher in the other groups: 23 +/- 4 (DOCA-salt), 25 +/- 2 (minoxidil), and 30 +/- 2 (DOCA-salt plus minoxidil). Mean arterial pressure (mm Hg) was increased in both DOCA-salt rats (160 +/- 8) and DOCA-salt plus minoxidil rats (153 +/- 5) as compared with sham-control (116 +/- 2) and minoxidil (113 +/- 3) rats. There was no significant difference in TPR between the sham-control and DOCA-salt rats, but TPR in minoxidil and DOCA-salt plus minoxidil rats was 30% and 28% lower than that in untreated sham-control and DOCA-salt hypertensive rats, respectively. In contrast, renal vascular resistance was significantly increased in both DOCA-salt groups as compared with non-DOCA-salt groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the haemodynamics of large arteries induced by single doses of nicardipine, enalapril, atenolol and urapidil

Haemodynamic changes in the carotid and brachial arteries produced by single doses of four anti-hypertensive drugs (nicardipine, enalapril, atenolol, and urapidil) have been studied in 12 patients with essential hypertension. Measurements were performed noninvasively using a mechanographic method and B-mode pulsed Doppler ultrasonography. Within 7 h all of the drugs had caused a significant reduction in blood pressure, whereas heart rate showed a significant change only after atenolol. All the drugs produced a marked reduction in brachial pulse-wave velocity. Only nicardipine caused a significant reduction in vessel wall tension both in the carotid and brachial arteries, while brachial peripheral resistance was significantly reduced by all the drugs except atenolol. Neither atenolol nor enalapril caused any significant reduction in carotid peripheral resistance. The results show that all four antihypertensive drugs led to a beneficial increase in arterial compliance despite their different effects on peripheral resistance.

Effects of carvedilol on renal function

A randomized, double-blind, placebo-controlled study was conducted to study the effects of acute and chronic administration of carvedilol in essential hypertension, with special emphasis on renal haemodynamics and function. Acute administration of a single dose of 50 mg carvedilol reduced systolic and diastolic blood pressure without inducing reflex tachycardia. Renal blood flow was preserved; accordingly, renal vascular resistance was significantly reduced. A significant reduction in the glomerular filtration rate and filtration fraction was observed. Plasma renin activity (PRA) and plasma aldosterone values were not changed. Chronic carvedilol treatment produced a significant fall in systolic and diastolic blood pressure, heart rate, PRA and plasma aldosterone. Renal blood flow, glomerular filtration rate and filtration fraction also remained unchanged; renal vascular resistance decreased significantly. It is concluded that carvedilol possesses definite antihypertensive and renal vasodilating properties, both acutely and after chronic treatment.

Treatment of severe hypertension with atenolol and betaxolol with once-daily regimens. Hemodynamic aspects

The effectiveness and safety of once-daily administration of drugs in the treatment of moderate to severe hypertension was studied. Forty men taking diuretics were randomized to atenolol (A, n = 18), 50 mg/day, or betaxolol (B, n = 22), a new B1-blocker, 20 mg/day, if their SDAP was 105 to 125 mm Hg at baseline (weeks 2 to 4). At week 6, if SDAP was greater than 95 mm Hg, minoxidil (M), 5.5 mg/day, was added. The patients were seen every two weeks to week 16 (end of drug titration) and then every four weeks to week 32. The dosages were increased to 200 mg/day for A, 80 mg/day for B, and 20 mg/day for M as needed. Physical examinations, chest x-ray films, ECGs, echocardiograms, spirometric studies, 24-h ambulatory arterial pressures (AAP), and blood chemistry analyses were done at baseline and during treatment. A and B combined with a diuretic (furosemide, F) and M decreased the arterial pressures and heart rates equally well by both clinical and AAP measurements (p less than .001). The IVS was decreased (p less than .05), whereas LVIDd, RVIDd, and cardiothoracic ratios were increased by both A and B (p less than .05, p less than .01). No changes were noted in LVPW, LVM, EF, FS, spirometric values, or blood chemistry analyses. Common side effects were weight gain, edema, and hypertrichosis. Once-daily administration of A or B in combination with F and M were effective in the treatment of moderate to severe hypertension. Although effective, prolonged use of M may lead to volume overload and cardiomegaly. The significance of these latter findings is not yet known.

Influence of minoxidil on myocardial hemodynamics, regional blood flow, and morphology in beagle dogs

Studies were made of the effects of two doses of minoxidil (3 mg/kg), given 24 hours apart, on cardiovascular hemodynamics, regional myocardial blood flow, and cardiac morphology in beagle dogs. Minoxidil caused increases in mean right atrial and left ventricular end-diastolic pressure. Systemic and pulmonary vascular resistance were reduced; cardiac output was increased. Left ventricular stroke work and the systolic pressure time index were unchanged by monoxidil administration. The diastolic pressure time index and ratio of diastolic/systolic pressure time index were decreased by minoxidil. Regional myocardial blood flow, measured with radioactive microspheres, increased in all regions of the heart except to the left ventricular papillary muscles. Minoxidil increased blood flow to left ventricular subendocardial tissue; however, this increase was significantly less than that observed in corresponding areas of subepicardial tissue, thus reducing the subendocardial/subepicardial tissue blood flow ratio. These results suggest that minoxidil is an effective peripheral vasodilator but may result in inadequate subendocardial perfusion. Morphologic studies disclosed two types of minoxidil-induced cardiac lesions: left ventricular papillary muscle necroses, and hemorrhagic lesions which were most prominent in right atrium and were associated with inflammation, intramural hemorrhage, and fibrinoid necrosis of small arteries. The papillary muscle necrosis were attributed to hypoxia. The atrial lesions were not of ischemic or hypoxic origin, because minoxidil did not decrease blood flow to atrial tissue. It is suggested that the atrial lesions are related to excessive vasodilation.

Hemodynamics of the carotid artery after vasodilation in essential hypertension

We performed simultaneous noninvasive measurements of common carotid artery and brachial artery hemodynamics in nine normal subjects and 10 subjects with sustained essential hypertension. In hypertensive subjects, brachial artery blood flow and forearm vascular resistance were in the normal range while carotid artery blood flow and carotid artery resistance were decreased and increased, respectively. The most important findings were the changes in the internal caliber of large arteries. Although the brachial and carotid artery diameters of hypertensive subjects were measured for the same level of mean arterial pressure, brachial artery diameter was significantly increased and carotid artery diameter was strictly normal as compared with values found in normal subjects. To assess whether carotid artery circulation could influence the baroreceptor reflex response to arteriolar vasodilation, carotid artery and brachial artery hemodynamics were measured in immediate succession in normotensive and hypertensive subjects before and after oral administration of cadralazine, a dihydralazine derivative. After cadralazine treatment, carotid artery tangential tension decreased in hypertensive subjects, and the changes were significantly correlated to the increase in heart rate. A similar correlation was found in normal subjects, but it was reset toward higher heart rates. These results indicate that the carotid artery does not behave like the brachial artery in response to a chronic increase in blood pressure. This behavior indicates intrinsic alterations of the arterial wall and might be involved in the resetting of the carotid baroreceptor reflex. Carotid artery circulation could play a role in hypertension by modulating the carotid baroreceptor mechanisms involved in the response to drug-induced arteriolar vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Nongenotoxicity of minoxidil in murine hair follicles as determined by the nuclear aberration assay

A 1-cm2 area on the back of CD1 mice was prepared for topical application of minoxidil, N-methyl-N-nitrosourea (MNU), or cyclophosphamide (CY) by clipping or plucking hair from a patch of skin. Plucking stimulates hair follicle cell division while clipping does not. Minoxidil was topically administered for 8 consecutive days. CY or MNU was administered topically once on the eighth day postplucking. The incidence of nuclear aberrations and mitotic figures were measured in hair follicles while frequency of micronuclei and the ratio of RBC/PCE were measured in the bone marrow. Results with minoxidil showed no increase in either nuclear aberrations in the hair follicle or micronuclei in the bone marrow. These results suggest that topically applied minoxidil is not genotoxic. In contrast, a dose-dependent effect of MNU on the incidence of nuclear aberrations in the hair follicle was seen. CY induced a dose-dependent increase in the incidence of micronuclei in the bone marrow and in nuclear aberrations in the hair follicle after topical application. Minoxidil applied to clipped mice significantly increased the incidence of mitotic figures above that seen in both the clipped and plucked controls. This suggests that minoxidil is a mitogenic agent in the hair follicle. These findings are consistent with the success of topically applied minoxidil in the treatment of alopecia areata.

Alternative pharmacologic approaches to the initial management of hypertension

Recent clinical trials in hypertension report more deaths due to coronary heart disease in mild hypertensives who received aggressive antihypertensive drug therapy and achieved better blood pressure control. Subset analyses of these trials suggest that diuretic therapy may have contributed to this outcome, possibly through a reduction in serum potassium or an elevation in serum lipids. Because of this, patients with an abnormal pretreatment electrocardiogram, history of myocardial infarction, unstable coronary heart disease, or diuretic-induced hyperlipidemia or hypokalemia unresponsive to management are candidates for alternative antihypertensive agents. A review of the literature suggests that most of the currently available beta-blockers, the alpha 1-antagonist prazosin, the angiotensin-converting enzyme inhibitor captopril, and the vasodilator hydralazine are effective alternatives to thiazide therapy in the initial management of hypertension and are recommended for particular subgroups of patients. Monotherapy with the centrally and peripherally acting sympatholytic agents is not recommended because of the frequent side effects encountered and the inferior hypotensive efficacy reported. Calcium channel blocking agents also appear to be suitable alternatives to thiazides in hypertension, but more experience with these is needed. Alternative pharmacologic agents may be selected on the basis of age, and, to a lesser extent, race.

Single and combined therapy for systemic hypertension with propranolol, hydralazine and hydrochlorothiazide: hemodynamic and neuroendocrine mechanisms of action

The antihypertensive mechanisms of single and combined therapy with a beta-adrenergic antagonist (propranolol) and a vasodilator (hydralazine) were investigated in 9 patients with moderately severe hypertension, who were receiving maintenance diuretic (hydrochlorothiazide) treatment. Hemodynamic and neuroendocrine responses were determined at rest and during lower body negative pressure, and dynamic and static exercise stress after the chronic administration of propranolol and hydralazine, given alone or in combination. All 3 drug regimens, each administered for at least 10 weeks, reduced blood pressure (p less than 0.05) compared with diuretic-only therapy in patients at rest, in both the supine and standing position, and during lower body negative pressure and dynamic exercise. There was a significant additive antihypertensive effect when propranolol and hydralazine were combined. Only combination therapy effectively lowered pressure during static exercise. The regimens produced divergent effects on the supine cardiac output: a decrease with propranolol (p less than 0.05), no change with combination therapy and an increase with hydralazine (p less than 0.05). Both hydralazine and combination therapy significantly reduced supine total peripheral resistance (p less than 0.05), whereas propranolol produced no change. All 3 drug treatments significantly reduced total peripheral resistance during upright rest and dynamic exercise (p less than 0.05), without changing cardiac output or maximal exercise capacity. During exercise, cardiac output was maintained in patients treated with propranolol and in those treated with combined therapy by increases in stroke volume (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Direct effects of minoxidil on epidermal cells in culture

Minoxidil, a potent antihypertensive agent, induces generalized hypertrichosis when administered systemically, or localized hair regrowth when applied topically to sites of severe alopecia areata. The pharmacologic mechanisms by which minoxidil stimulates hair growth are unknown. This study was designed to examine whether minoxidil has direct effects on neonatal murine epidermal cells in culture. In the presence of minoxidil, cultures showed a marked dose-dependent second peak of DNA synthesis 8-10 days after culture initiation. In addition, two morphologically distinct cell types appeared. Indirect immunofluorescence staining with keratin-specific antibody revealed cytoplasmic keratin fibers, suggesting the epidermal origin of these cells. Our experiments demonstrate that minoxidil can affect epidermal cells in culture by altering their growth pattern and phenotypic appearance.

Long-term effects of captopril on renal function in hypertensive patients

The effect of captopril up to 450 mg/day on blood pressure and renal function were investigated during sustained treatment of 10 patients whose severe hypertension had not responded to previous therapy. All the patients were kept on diuretics and most of them on beta-blockers, too. A control determination of glomerular filtration rate (GFR) and para-aminohippuric acid clearance (CPAH) was performed during the prior treatment. The effect of the addition (or substitution) of captopril were assessed after an average of 25 days (short-term) and 26 weeks (long-term). Short-term treatment produced a 15.5% decrease in mean blood pressure and interindividually variable effects on renal function. On average GFR was somewhat lower and CPAH slightly higher than the control values (not significant). This pattern is quite similar to the effects of most other antihypertensive drugs. On long-term therapy GFR rose by a mean of 9% (NS) and CPAH by 17% (p less than 0.02). However, in a patient who developed a captopril-induced nephrotic syndrome, GFR dropped to 56% and CPAH to 50% of the control values. In another patient a transient rise in serum creatinine accompanied a severe drug reaction.

Antihypertensives and their impact on renal function

Antihypertensive agents possess many properties that could cause alterations in renal function. These are: alterations in systemic hemodynamics, changes in the renin-angiotensin aldosterone system, direct intrarenal effects, and alterations in salt and water metabolism. This article reviews the antihypertensive agents in general usage and major points are made concerning potential deleterious effects of methyldopa and nonselective beta-adrenergic blocking drugs on renal function. In particular, recent data are shown concerning the effects of labetalol on renal function indicating the absence of decrements in glomerular filtration rate and renal plasma flow in patients with normal renal function and in patients with mild to moderate renal insufficiency. A possible decrease in these parameters in patients with severe renal insufficiency is presented and discussed.

Effects of labetalol on the arachidonic acid metabolism in human blood platelets, and in lung and aorta of the rat

Effects of labetalol on the arachidonic acid metabolism in washed human blood platelets, and in lung and aorta of the rat was studied. Effects of this drug on the aggregation induced by usual aggregation agents, and on the prostacyclin generating capacity of rat aorta as assessed by its antiaggregation effect were also studied. The following results were obtained. 1. Reduced generation of thromboxane and HHT in platelets was observed at 1 mM conc. of the drug. 2. This drug inhibited ADP-, collagen-, and epinephrine-induced aggregation in a dose dependent manner. 3. Arachidonate-induced aggregation was only slightly inhibited at 1 mM conc. of labetalol. 4. Aorta and lung synthesized more prostacyclin in its presence from exogenous labelled arachidonate. 5. Aorta synthesized more prostacyclin from its endogenous AA pool in the presence of labetalol as assessed by inhibition of platelet aggregation.