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

Cardiovascular/Pulmonary Medications and Male Reproduction

Cardiovascular and respiratory medications are used by men of reproductive age although use of the former is most prevalent in advanced age. Many of these drugs have been associated with sexual dysfunction, including erectile and ejaculatory dysfunction, but for most there is insufficient evidence to link their use with testicular dysfunction, reduced semen quality or infertility. Some exceptions are the irreversible α₁-adrenergic antagonist phenoxybenzamine, which carries a high risk of retrograde ejaculation; the specific α_1A-adrenergic antagonists silodosin and tamsulosin, used primarily to treat BPH/lower urinary tract symptoms, which can cause retrograde ejaculation; and the peripheral β₁-adrenergic antagonist atenolol, used to treat hypertension, which may decrease testosterone/free-testosterone levels. In this chapter, we review the evidence available regarding adverse reactions on male reproduction of adrenergic receptor agonists/antagonists, calcium channel blockers, angiotensin converting enzyme (ACE) inhibitors, diuretics, digoxin, and hydralazine. For some of these medications, there is some evidence for male reproductive effects, along with some solid work in experimental and companion animal species suggesting negative effects. In contrast, and of special note, are calcium channel blockers, which have long been included on lists of medications with the potential to cause male infertility. This turns out to be a good example of a substance with profound effects on sperm function in vitro, but with limited evidence for in vivo effects on semen quality or fertility, even in experimental species. We hope that the evidence provided in this chapter will stimulate additional studies for these important classes of medications.

Long-term effects on sexual function of five antihypertensive drugs and nutritional hygienic treatment in hypertensive men and women. Treatment of Mild Hypertension Study (TOMHS)

Problems with sexual function have been a long-standing concern in the treatment of hypertension and may influence the choice of treatment regimens and decisions to discontinue drugs. The Treatment of Mild Hypertension Study (TOMHS) provides an excellent opportunity for examination of sexual function and effects of treatment on sexual function in men and women with stage I diastolic hypertension because of the number of drug classes studied, the double-blind study design, and the long-term follow-up. TOMHS was a double-blind, randomized controlled trial of 902 hypertensive individuals (557 men, 345 women), aged 45 to 69 years, treated with placebo or one of five active drugs (acebutolol, amlodipine maleate, chlorthalidone, doxazosin maleate, or enalapril maleate). All participants received intensive lifestyle counseling regarding weight loss, dietary sodium reduction, alcohol reduction (for current drinkers), and increased physical activity. Sexual function was ascertained by physician interviews at baseline and annually during follow-up. At baseline, 14.4% of men and 4.9% of women reported a problems with sexual function. In men, 12.2% had problems obtaining and/or maintaining an erection; 2.0% of women reported a problem having an orgasm. Erection problems in men at baseline were positively related to age, systolic pressure, and previous antihypertensive drug use. The incidences of erection dysfunction during follow-up in men were 9.5% and 14.7% through 24 and 48 months, respectively, and were related to type of antihypertensive therapy. Participants randomized to chlorthalidone reported a significantly higher incidence of erection problems through 24 months than participants randomized to placebo (17.1% versus 8.1%, P = .025). Incidence rates through 48 months were more similar among treatment groups than at 24 months, with nonsignificant differences between the chlorthalidone and placebo groups. Incidence was lowest in the doxazosin group but was not significantly different from the placebo group. Incidence for acebutolol, amlodipine, and enalapril groups was similar to that in the placebo group. In many cases, erection dysfunction did not require withdrawal of medication. Disappearance of erection problems among men with problems at baseline was common in all groups but greatest in the doxazosin group. Incidence of reported sexual problems in women was low in all treatment groups. In conclusion, long-term incidence of erection problems in treated hypertensive men is relatively low but is higher with chlorthalidone treatment. Effects of erection dysfunction with chlorthalidone appear relatively early and are often tolerable, and new occurrences after 2 years are unlikely. The rate of reported sexual problems in hypertensive women is low and does not appear to differ by type of drug. Similar incidence rates of erection dysfunction in placebo and most active drug groups caution against routine attribution of erection problems to antihypertensive medication.

Effects of four beta-adrenergic receptor antagonists on male rat sexual behavior

Antihypertensive medication has been reported to cause serious sexual side effects in men. Frequently mentioned as causing sexual dysfunction are beta-adrenergic receptor antagonists. The purpose of this study was to examine in detail the effects of beta blockers on adult male rat sexual behavior. Thirty minutes following a single subcutaneous injection of propranolol, pindolol, atenolol or labetalol, mating tests were conducted. The mixed beta 1- and beta 2-adrenergic antagonists, propranolol and pindolol, profoundly inhibited male sexual behavior. At the 5 and 10 mg/kg doses, propranolol inhibited ejaculatory behavior to the extent that only 9.1 and 8.3% respectively showed the behavior while pindolol reduced this behavior to 36.4% (16 mg/kg). These drugs also adversely affected various parameters of behavior in a dose-dependent manner. The selective beta 1 antagonist, atenolol, had only minor effects and labetalol even less so at the doses tested. It was suggested that the strongly inhibitory effects of propranolol and pindolol on male rat sex behavior may well be due to their 5-HT1A antagonistic binding properties rather than their beta-antagonistic properties.

Assessment of erectogenic drugs by numeric plethysmography

A method of assessment of the erection in man, using numeric penile plethysmography, is presented. The data concerning the sensor, the electronic circuit, and the computer interfacing with an IBM PC are described. As a validation of this method, apomorphine (0.009 mg/kg) was tested in a double-blind, placebo-controlled study, carried out in healthy volunteers. Apomorphine induced an erection starting, as a mean, at the fourth minute postinjection. The treatment increased the penis volume without any other stimulation (p = 0.0008) and potentiated the physiologic response induced by visual erotic stimulation (p = 0.0012). The limits of plethysmography are discussed in reference to rigidimetry.

Ejaculatory failure and urinary dysfunction secondary to labetalol

We describe 3 men with moderate to severe essential hypertension in whom ejaculatory failure developed after therapy with labetalol, an antihypertensive drug with alpha-1 and beta-adrenergic blocking properties. No decrease in libido or erectile dysfunction was reported by any of the patients. Previous and subsequent antihypertensive therapy with either alpha or beta-adrenergic blocking agents failed to cause similar symptoms. These findings reveal a unique spectrum of genitourinary dysfunction associated with the multireceptor blocking properties of labetalol.

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)