The effect of labetalol and propranolol on the pressor response to sexual arousal in women

Risk of amputation in patients with diabetic foot ulcers: a claims-based study

The objective of this study was to undertake a retrospective analysis of claims data of diabetic foot ulcer (DFU) patients to determine the rates of amputation and identify the risk and protective factors. Rates of amputation were calculated in patients diagnosed with DFU in the MEDSTAT Marketscan database between January 2000 and December 2002, who had prediagnosis coverage of 90 days. A nested case-control study was conducted using a 1 : 10 ratio of amputee cases to randomly selected nonamputee controls matched on follow-up days. The association of co-morbid conditions, demographic factors, and severity (5+ outpatient claims for DFU) on amputation was estimated by adjusted odds ratios (AOR) with 95% confidence intervals (CIs). The 5911 eligible patients yielded an incidence density rate of 2.30 amputations per 100 person years (95% CI = 1.91, 2.77). The 116 cases and 1153 controls averaged 307.3 and 308.5 observation days, respectively. Amputation was significantly increased by male gender (AOR 1.98), Charlson co-morbidity scores of 4-5 and 6+ (AOR = 2.89 and 5.36, respectively), renal disease (AOR = 2.11), peripheral vascular disease (AOR = 2.67), and 5+ outpatient DFU services (AOR = 2.17). Practitioners may consider more aggressive care and earlier referral to specialists for DFU patients who fit risk profiles for amputation, which include peripheral vascular disease, multiple co-morbid conditions, and repeated outpatient DFU services.

A review of the physiology and pharmacology of peripheral (vaginal and clitoral) female genital arousal in the animal model

PURPOSE

We review contemporary scientific data concerning the physiology and pharmacology of peripheral female genital arousal responses in the animal (rabbit and rat) model.

MATERIALS AND METHODS

We reviewed the contemporary literature and our research studies concerning physiology and pharmacology of peripheral genital arousal from 3 experimental animal models, including genital smooth muscle cell culture, genital strip organ bath and in vivo animal model studies.

RESULTS

Nitric oxide (NO) appears to be a key pathway mediating clitoral smooth muscle relaxation. In the vagina NO appeared to have a more controversial role in mediating vaginal muscularis smooth muscle relaxation. Vasoactive intestinal polypeptide induced vaginal smooth muscle relaxation. Functional alpha-adrenergic receptors were expressed in the clitoris and vagina, and mediated norepinephrine induced genital smooth muscle contraction. Androgens and estrogens modulated distinct physiological responses in vagina, and androgens facilitated vaginal smooth muscle relaxation. Papaverine hydrochloride, a smooth muscle relaxant, and phentolamine mesylate, an alpha-blocker, administered into the vaginal spongy muscularis layer increased vaginal wall pressure and vaginal blood flow. Sildenafil caused significant increases in genital (clitoral and vaginal) blood flow and vaginal lubrication in intact and ovariectomized animals. This response was more pronounced in animals treated with estradiol, suggesting that the NO cyclic guanosine monophosphate pathway is involved in the physiological mechanism of female genital arousal and that sildenafil facilitates this response in an in vivo animal model.

CONCLUSIONS

To achieve improved understanding of the biological aspects of female sexual function, further research is needed in the physiology and pharmacology of peripheral (clitoral and vaginal) genital arousal in the animal model.

Biology of female sexual function

Although the psychosocial and relationship aspects of female sexuality have been extensively investigated, studies concerning the anatomy, physiology and pathophysiology of female sexual function and dysfunction are limited. The paucity of biologic data may be attributed to a lack of reliable experimental models and tools for investigating female sexual function and to limited funding, which is critical for developing experimental approaches. Research efforts by several investigators in different laboratories have been establishing experimental models needed for investigating the physiologic mechanisms involved in the genital arousal response of sexual function. These experimental models have permitted assessment of genital hemodynamics, vaginal lubrication, regulation of genital smooth muscle contractility and signaling pathways, providing preliminary information about the role of neurotransmitters and sex steroid hormones in sexual function. Further research is needed to define the neurotransmitters responsible for vaginal smooth muscle relaxation and the role of sex steroid hormones and their receptors in modulating genital hemodynamics, smooth muscle contractility, and neurotransmitter receptor expression. Finally, a global and integral understanding of the biologic aspects of female sexual function requires investigation of the vascular, neurologic (central and peripheral), and structural components of this extremely complex physiologic process.

Inhibition of subjective and physiological sexual arousal in women by clonidine

OBJECTIVE

The present investigation was designed to provide the first empirical examination of the effects of clonidine, a selective alpha 2-adrenergic agonist, on sexual arousal in women with and without prior sympathetic nervous system [SNS] stimulation by exercise. The purpose was to help elucidate the influence of adrenergic mechanisms on sexual function in women.

METHODS

Thirty sexually functional women participated in two experimental sessions in which subjective (self-report) and physiological (vaginal photoplethysmograph) sexual responses to erotic stimuli were measured after either clonidine (0.2 mg) or placebo administration in a randomized, double-blind, crossover protocol. Before viewing the experimental films, 15 subjects engaged in 20 minutes of intense exercise designed to elicit significant SNS activation.

RESULTS

Clonidine significantly decreased vaginal pulse amplitude, vaginal blood volume, and subjective sexual responses to the erotic films in subjects who were in a state of heightened (via exercise), but not baseline (no exercise) SNS arousal.

CONCLUSIONS

Clonidine can significantly inhibit subjective and physiological sexual arousal in women. These findings have implications for deriving an etiological theory of sexual function in women and for understanding the effects of psychotherapeutic drugs on female sexual function.

Sexual function in women. Do antihypertensive drugs have an impact?

Drug-induced sexual dysfunction is well known to occur with antihypertensive drugs in men. There are much less data on the effects of drugs on female sexual function. The physiology of the female sexual response has similarities to that of the male sexual response and there are therefore good reasons for suspecting that antihypertensive drugs are likely to adversely affect sexual function in women. Present evidence suggests that clonidine, methyldopa, guanethidine and reserpine are associated with adverse effects on sexual function. In healthy volunteers, labetalol appears to reduce vaginal lubrication, but there are no studies in patients receiving the drug therapeutically. Thiazide diuretics may be associated with the worsening of sexual problems, which interestingly appear to be ameliorated by weight reduction. Present evidence on the effects of vasodilators is limited but the evidence suggests that sexual function in women receiving calcium antagonists is not altered by changing to an angiotensin converting enzyme (ACE) inhibitor. Although present evidence suggests that effects on female sexual function may not be very great, it should be recognised that there are very few data in this area. Further work is clearly necessary.

Combined alpha- and beta-receptor inhibition in the treatment of hypertension

Both beta- and alpha-adrenergic mechanisms are important in the control of blood pressure; alpha-mediated vasoconstriction is responsible for the regulation of vascular tone, and beta-mediated responses stimulate the heart directly and indirectly by liberating renin and affecting vascular smooth muscle tone. beta-Adrenergic blocking drugs have long been established in the treatment of hypertension. The development of drugs which combine this action with an alpha-blocking effect represents an additional mode of action to lower the blood pressure. Numerous studies have demonstrated that labetalol intravenously or orally gives a rapid fall of blood pressure in essential and renal hypertension. It has also been used intravenously in phaeochromocytoma, tetanus, clonidine withdrawal, and as an adjunct to halothane to produce hypotensive anaesthesia. Intravenously, labetalol is probably best given as a graded infusion or as repeated small bolus injections to assure a smooth fall of blood pressure. Many long term studies have shown it to be effective orally in prolonged treatment of hypertension with studies of over 5 years, showing that tolerance does not develop. Labetalol can be used in combination with diuretics and other drugs when necessary. It can be employed to control the blood pressure in all grades of hypertension. A dosage of 100mg twice daily will often be adequate to control mild hypertension and the use of even lower doses has been reported. However, the dosage can be markedly increased in severe hypertension and while such doses are relatively exceptional, several trials have employed over 2 g per day for the more resistant cases. Studies have demonstrated that blood pressure control with labetalol is equivalent to that with beta-adrenoceptor blocking drugs plus vasodilators, or methyldopa. Labetalol has been used in patients with severe renal impairment and a number of studies suggest that it may now be the drug of choice in raised blood pressure of pregnancy. Side effects can be divided into those related to beta-blockade, those related to alpha-blockade and those not clearly related to either effect. It has been suggested that the side effects attributable to the beta-blocking component are less obtrusive than those seen with pure beta-blocking drugs without alpha-activity because the alpha-blockade modifies the consequences of beta-blockade. Heart failure has been reported, but for haemodynamic reasons would be expected to be less common; careful patient selection should avoid any risk. Similarly labetalol may worsen asthma even if the risks are probably less than with non-selective beta-blockade alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Labetalol: a review of its pharmacology, pharmacokinetics, clinical uses and adverse effects

Labetalol is a combined alpha- and beta-adrenoceptor blocking agent for oral and intravenous use in the treatment of hypertension. It is a nonselective antagonist at beta-adrenoceptors and a competitive antagonist of postsynaptic alpha 1-adrenoceptors. Labetalol is more potent at beta that at alpha 1 adrenoceptors in man; the ratio of beta-alpha antagonism is 3:1 after oral and 6.9:1 after intravenous administration. Labetalol is readily absorbed in man after oral administration, but the drug, which is lipid soluble, undergoes considerable hepatic first-pass metabolism and has an absolute bioavailability of approximately 25%. There are no active metabolites, and the elimination half-life of the drug is approximately 6 hours. Unlike conventional beta-adrenoceptor blocking drugs without intrinsic sympathomimetic activity, labetalol, when given acutely, produces a decrease in peripheral vascular resistance and blood pressure with little alteration in heart rate or cardiac output. However, like conventional beta-blockers, labetalol may influence the renin-angiotensin-aldosterone system and respiratory function. Clinical studies have shown that the antihypertensive efficacy of labetalol is superior to placebo and to diuretic therapy and is at least comparable to that of conventional beta-blockers, methyldopa, clonidine and various adrenergic neuronal blockers. Labetalol administered alone or with a diuretic is often effective when other antihypertensive regimens have failed. Studies have shown that labetalol is effective in the treatment of essential hypertension, renal hypertension, pheochromocytoma, pregnancy hypertension and hypertensive emergencies. In addition, preliminary studies indicate that labetalol may be of value in the management of ischemic heart disease. The most troublesome side effect of labetalol therapy is posture-related dizziness. Other reported side effects of the drug include gastrointestinal disturbances, tiredness, headache, scalp tingling, skin rashes, urinary retention and impotence. Side effects related to the beta-adrenoceptor blocking effect of labetalol, including asthma, heart failure and Raynaud's phenomenon, have been reported in rare instances.

A method for monitoring drug effects on male sexual response: the effect of single dose labetalol

1 A method for monitoring the effect of drugs on the genital response to stimulation provided by vibration is described. 2 Using this method, the effect on male sexual response of two oral doses (100 mg and 300 mg) labetalol were studied and compared with placebo in six subjects. 3 Labetalol did not affect the attainment or maintenance of erection. 4 Labetalol delayed ejaculation in a dose-related manner. 5 Labetalol treatment resulted in a significant dose-related delay in detumescence.