Interactions between drugs for erectile dysfunction and drugs for cardiovascular disease

Alprostadil vs. isosorbide dinitrate in ameliorating angina episodes in patients with coronary slow flow phenomenon: A randomized controlled trial

Background

The optimum therapy for coronary slow flow phenomenon (CSFP) stays debatable. This study compared the effectiveness of alprostadil with isosorbide dinitrate in alleviating angina episodes in CSFP patients.

Methods

In this prospective, randomized controlled study, 102 patients with CSFP without severe coronary artery stenosis that exhibited stable angina were allocated randomly in a ratio of 1:1 to either the alprostadil group (40 μg, three times per day, n = 51) or the isosorbide dinitrate group (5 mg, three times per day, n = 51). Frequency of angina events, intensity of suffering, and the Canadian Cardiovascular Society (CCS) grading of angina pectoris were evaluated at baseline and one month after. Additionally, the Seattle Angina Questionnaire (SAQ) was assessed.

Results

Baseline characteristics were comparable between the two groups. At 1-month follow-up, patients administered with alprostadil experienced fewer angina episodes [episodes per week, 1 (2) vs. 2 (2), P < 0.001] and less pain intensity [self-evaluated pain score, 2 (3) vs. 3 (4), P < 0.001] than those with isosorbide dinitrate. In the alprostadil group, 78.4% of patients were classified as CCS class I, significantly higher than the 47.1% seen in the isosorbide dinitrate group (P = 0.001). Furthermore, treatment of alprostadil led to a significant improvement in the SAQ score (7.09 U, 95% CI: 4.22–9.96, P < 0.001) compared to isosorbide dinitrate. Additionally, fewer patients suffered headaches when receiving alprostadil (7.8% vs. 19.6%, P = 0.084).

Conclusion

Alprostadil was more effective in ameliorating angina symptoms in CSFP patients than isosorbide dinitrate.

Clinical trial registration

[www.chictr.org.cn], identifier [ChiCTR2000033233].

Pharmacokinetic Drug Interaction Between Amlodipine and Tadalafil: An Open-Label, Randomized, Multiple-Dose Crossover Study in Healthy Male Volunteers

Purpose

The combined administration of tadalafil, a phosphodiesterase-5 inhibitor, and amlodipine, a calcium channel blocker, can be a promising therapeutic option for hypertension patients with erectile dysfunction. This study aimed to examine the pharmacokinetic drug interaction between tadalafil and amlodipine and the tolerability of their combined administration in healthy male subjects.

Subjects and Methods

Healthy volunteers (N = 24) were randomly assigned to one of the six sequences that consisted of three treatments: tadalafil (5 mg) alone, amlodipine (10 mg) alone, and tadalafil plus amlodipine. The study drugs were administered orally for 9 d, and the collected serial blood samples were analyzed up to 72 h after the last dosing. Pharmacokinetic parameters were calculated using non-compartmental analysis.

Results

For tadalafil, geometric mean ratios (GMRs) (90% confidence interval (CI)) of the combined therapy over the monotherapy were 1.57 (1.46–1.68) for AUC_τ,ss and 1.34 (1.24–1.45) for C_max,ss. For amlodipine, the GMRs (90% CI) of AUC_τ,ss and C_max,ss were 0.93 (0.90–0.97) and 0.95 (0.91–0.99), respectively. The severity of all observed adverse events (AEs) related to the study drugs was mild, and the frequency of AEs of the combined administration was not significantly different from the monotherapy.

Conclusion

A substantial pharmacokinetic drug interaction between tadalafil and amlodipine was observed with respect to the concentration of tadalafil when administered concomitantly. However, the dose range of the combined administration of tadalafil and amlodipine in the present study was well tolerated by the subjects.

Efficacy of Aspirin for Vasculogenic Erectile Dysfunction in Men: A Meta-Analysis of Randomized Control Trials

One of the major causes of erectile dysfunction (ED) is an endothelial vascular disorder. This meta-analysis is performed to determine the efficacy of aspirin on erectile function in men with vasculogenic ED. For this purpose, CENTRAL, MEDLINE, and reference lists of articles up to November 2019 were searched. Randomized controlled trials (RCTs) were selected that compared aspirin with placebo in men of any ethnicity with vasculogenic ED. A total of 58 trials were retrieved. Finally, two trials of 214 men fulfilled our selection criteria. High selection and detection bias were identified for one trial. The participants showed a significant improvement in erectile function when they took aspirin (mean difference: 5.14, 95% CI [3.89, 6.40], and I² = 0%). Although the present meta-analysis suggested that aspirin has a significant effect on the improvement of erectile function, there were limited RCTs available on this topic and doses of aspirin varied. Additional studies are needed to support findings from this meta-analysis. Aspirin needs to be considered by practitioners when prescribing drugs for vasculogenic ED.

Erectile Dysfunction and Ischaemic Heart Disease

Erectile dysfunction (ED) is a common disorder that affects the quality of life of many patients. It is prevalent in more than half of males aged over 60 years. Increasing evidence suggests that ED is predominantly a vascular disorder. Endothelial dysfunction seems to be the common pathological process causing ED. Many common risk factors for atherosclerosis such as diabetes, hypertension, smoking, obesity and hyperlipidaemia are prevalent in patients with ED and so management of these common cardiovascular risk factors can potentially prevent ED. Phosphodiesterase type 5 inhibitors provide short-term change of haemodynamic factors to help initiate and maintain penile erection. They have been shown to be an effective and safe treatment strategy for ED in patients with heart disease, including those with ischaemic heart disease and hypertension.

Advanced glycation end-products: a common pathway in diabetes and age-related erectile dysfunction

Reactive derivatives of non-enzymatic glucose-protein condensation reactions integrate a heterogeneous group of irreversible adducts called advanced glycation end-products (AGEs). Numerous studies have investigated the role of the AGEs in cardiovascular system; however, its contribution to erectile dysfunction (ED) that is an early manifestation of cardiovascular disease has been less intensively investigated. This review summarizes the most recent advances concerning AGEs effects in the cavernous tissue of the penis and in ED onset, particularly on diabetes and aging, conditions that not only favor AGEs formation, but also increase risk of developing ED. The specific contribution of AGE on intra- and extracellular deposition of insoluble complexes, interference in activity of endothelial nitric oxide (NO) synthase, NO bioavailability, endothelial-dependent vasodilatation, as well as molecular pathways activated by receptor of AGEs are presented. Finally, the interventional actions that prevent AGEs formation, accumulation or activity in the cavernous tissue and that include nutritional pattern modulation, nutraceuticals, exercise, therapeutic strategies (statins, anti-diabetics, inhibitors of phosphodiesterase-5, anti-hypertensive drugs) and inhibitors of AGEs formation and crosslink breakers, are discussed. From this review, we conclude that despite the experiments conducted in animal models pointing to the AGE/RAGE axis as a potential interventional target with respect to ED associated with diabetes and aging, the clinical data have been very disappointing and, until now, did not provide evidence of benefits of treatments directed to AGE inactivation.

Sexual function in patients with chronic angina pectoris

Drugs for erectile dysfunction (ED) may be contraindicated with nitrates commonly used to treat patients with angina pectoris, and certain antianginal therapies may worsen ED. The American Heart Association and the Princeton Consensus Conference panel of experts recommend that patients with coronary artery disease and ED who experience angina pectoris undergo full medical evaluations to assess the cardiovascular risks associated with resuming sexual activity before being prescribed therapy for ED. Current antianginal therapies include β blockers, calcium channel blockers, short- and long-acting nitrates, and ranolazine, a late sodium current inhibitor. Short- and long-acting nitrates remain a contraindication with phosphodiesterase-5 inhibitors commonly used to treat patients with ED, and the benefits of the other antianginal therapies must be weighed against their effects on cardiovascular health and erectile function. In conclusion, patients with coronary artery disease and ED who wish to initiate phosphodiesterase-5 inhibitor therapy and need to discontinue nitrate therapy need treatment options that manage their angina pectoris effectively, maintain their cardiovascular health, and provide the freedom to maintain their sexual function.

Clinical outcomes and management of mechanism-based inhibition of cytochrome P450 3A4

Mechanism-based inhibition of cytochrome P450 (CYP) 3A4 is characterized by NADPH-, time-, and concentration-dependent enzyme inactivation, occurring when some drugs are converted by CYPs to reactive metabolites. Such inhibition of CYP3A4 can be due to the chemical modification of the heme, the protein, or both as a result of covalent binding of modified heme to the protein. The inactivation of CYP3A4 by drugs has important clinical significance as it metabolizes approximately 60% of therapeutic drugs, and its inhibition frequently causes unfavorable drug–drug interactions and toxicity. The clinical outcomes due to CYP3A4 inactivation depend on many factors associated with the enzyme, drugs, and patients. Clinical professionals should adopt proper approaches when using drugs that are mechanism-based CYP3A4 inhibitors. These include early identification of drugs behaving as CYP3A4 inactivators, rational use of such drugs (eg, safe drug combination regimen, dose adjustment, or discontinuation of therapy when toxic drug interactions occur), therapeutic drug monitoring, and predicting the risks for potential drug–drug interactions. A good understanding of CYP3A4 inactivation and proper clinical management are needed by clinical professionals when these drugs are used.

Anatomy, physiology, and pathophysiology of erectile dysfunction

INTRODUCTION

Significant scientific advances during the past 3 decades have deepened our understanding of the physiology and pathophysiology of penile erection. A critical evaluation of the current state of knowledge is essential to provide perspective for future research and development of new therapies.

AIM

To develop an evidence-based, state-of-the-art consensus report on the anatomy, physiology, and pathophysiology of erectile dysfunction (ED).

METHODS

Consensus process over a period of 16 months, representing the opinions of 12 experts from seven countries.

MAIN OUTCOME MEASURE

Expert opinion was based on the grading of scientific and evidence-based medical literature, internal committee discussion, public presentation, and debate.

RESULTS

ED occurs from multifaceted, complex mechanisms that can involve disruptions in neural, vascular, and hormonal signaling. Research on central neural regulation of penile erection is progressing rapidly with the identification of key neurotransmitters and the association of neural structures with both spinal and supraspinal pathways that regulate sexual function. In parallel to advances in cardiovascular physiology, the most extensive efforts in the physiology of penile erection have focused on elucidating mechanisms that regulate the functions of the endothelium and vascular smooth muscle of the corpus cavernosum. Major health concerns such as atherosclerosis, hyperlipidemia, hypertension, diabetes, and metabolic syndrome (MetS) have become well integrated into the investigation of ED.

CONCLUSIONS

Despite the efficacy of current therapies, they remain insufficient to address growing patient populations, such as those with diabetes and MetS. In addition, increasing awareness of the adverse side effects of commonly prescribed medications on sexual function provides a rationale for developing new treatment strategies that minimize the likelihood of causing sexual dysfunction. Many basic questions with regard to erectile function remain unanswered and further laboratory and clinical studies are necessary.

Application of mechanism-based CYP inhibition for predicting drug-drug interactions

BACKGROUND

A mechanism-based inhibition of CYPs is characterized by NADPH-, time- and concentration-dependent enzyme inactivation and substrate protection. A significant inactivation of CYPs and particularly the main human hepatic and intestinal CYPs could result in clinical drug-drug interactions (DDIs) and adverse drug reactions.

OBJECTIVE

To address whether DDIs owing to mechanism-based CYP inhibition is predictable based on in vitro inhibitory data.

METHOD

Medline (by means of PubMed up to 26 March 2009) has been searched using proper relevant terms.

RESULT/CONCLUSION

It is possible to predict DDIs caused by mechanism-based CYP inhibition, although the in vitro data do not necessarily translate directly into relative extents of inhibition in vivo because in vivo clinical consequences depend on additional factors that are not easily accounted for in vitro and for reversible inhibition. Incorporation of other important parameters such as CYP degradation rate (k(deg)), relative contribution of the CYP inactivated to the victim drug elimination (f(m(CYP))) and inhibition of intestinal CYP-mediated first-pass metabolism of the object drug (F'(gut)/F(gut) ratio) into the prediction models significantly improves the prediction. Uncertainty of the prediction is mainly from the variability in the estimates of these critical parameters.

Toxicological Significance of Mechanism-Based Inactivation of Cytochrome P450 Enzymes by Drugs

Cytochrome P450 (P450) enzymes oxidize xenobiotics into chemically reactive metabolites or intermediates as well as into stable metabolites. If the reactivity of the product is very high, it binds to a catalytic site or sites of the enzyme itself and inactivates it. This phenomenon is referred to as mechanism-based inactivation. Many clinically important drugs are mechanism-based inactivators that include macrolide antibiotics, calcium channel blockers, and selective serotonin uptake inhibitors, but are not always structurally and pharmacologically related. The inactivation of P450s during drug therapy results in serious drug interactions, since irreversibility of the binding allows enzyme inhibition to be prolonged after elimination of the causal drug. The inhibition of the metabolism of drugs with narrow therapeutic indexes, such as terfenadine and astemizole, leads to toxicities. On the other hand, the fate of P450s after the inactivation and the toxicological consequences remains to be elucidated, while it has been suggested that P450s modified and degraded are involved in some forms of tissue toxicity. Porphyrinogenic drugs, such as griseofulvin, cause mechanism-based heme inactivation, leading to formation of ferrochelatase-inhibitory N-alkylated protoporphyrins and resulting in porphyria. Involvement of P450-derived free heme in halothane-induced hepatotoxicity and catalytic iron in cisplatin-induced nephrotoxicity has also been suggested. Autoantibodies against P450s have been found in hepatitis following administration of tienilic acid and dihydralazine. Tienilic acid is activated by and covalently bound to CYP2C9, and the neoantigens thus formed activate immune systems, resulting in the formation of an autoantibodydirected against CYP2C9, named anti-liver/kidney microsomal autoantibody type 2, whereas the pathological role of the autoantibodies in drug-induced hepatitis remains largely unknown.

Clinically important drug interactions potentially involving mechanism-based inhibition of cytochrome P450 3A4 and the role of therapeutic drug monitoring

Cytochrome P450 (CYP) 3A4 is the most abundant enzyme of CYPs in the liver and gut that metabolizes approximately 50% currently available drugs. A number of important drugs have been identified as substrates, inducers, and/or inhibitors of CYP3A4. The substrates of CYP3A4 considerably overlap with those of P-glycoprotein. Both CYP3A4 and P-glycoprotein are subject to inhibition and induction by a number of factors. Mechanism-based inhibition of CYP3A4 is characterized by NADPH-, time-, and concentration-dependent enzyme inactivation occurring when some xenobiotics or drugs are converted by CYPs to reactive metabolites. Such an inhibition of CYP3A4 is caused by chemical modification of the heme, the protein, or both as a result of covalent binding of modified heme to the protein. To date, the identified clinically important mechanism-based CYP3A4 inhibitors mainly include macrolide antibiotics (eg, clarithromycin and erythromycin), anti-HIV agents (eg, ritonavir and delavirdine), antidepressants (eg, fluoxetine and fluvoxamine), calcium channel blockers (eg, verapamil and diltiazem), steroids and their modulators (eg, gestodene and mifepristone), and several herbal and dietary components. The inactivation of CYP3A4 by drugs often causes unfavorable and long-lasting drug-drug interactions and probably fatal toxicity, depending on many factors associated with the enzyme, drugs, and the patients. Clinicians are encouraged to have a sound knowledge of drug-induced, mechanism-based CYP3A4 inhibition; take proper cautions, and perform close monitoring for possible drug interactions when using drugs that are mechanism-based CYP3A4 inhibitors. To minimize drug-drug interactions involving mechanism-based CYP3A4 inhibition, it is necessary to choose safe drug combination regimens, adjust drug dosages appropriately, and conduct therapeutic drug monitoring for drugs with narrow therapeutic indices.

Drug-induced changes in P450 enzyme expression at the gene expression level: a new dimension to the analysis of drug-drug interactions

Drug-drug interactions (DDIs) caused by direct chemical inhibition of key drug-metabolizing cytochrome P450 enzymes by a co-administered drug have been well documented and well understood. However, many other well-documented DDIs cannot be so readily explained. Recent investigations into drug and other xenobiotic-mediated expression changes of P450 genes have broadened our understanding of drug metabolism and DDI. In order to gain additional information on DDI, we have integrated existing information on drugs that are substrates, inhibitors, or inducers of important drug-metabolizing P450s with new data on drug-mediated expression changes of the same set of cytochrome P450s from a large-scale microarray gene expression database of drug-treated rat tissues. Existing information on substrates and inhibitors has been updated and reorganized into drug-cytochrome P450 matrices in order to facilitate comparative analysis of new information on inducers and suppressors. When examined at the gene expression level, a total of 119 currently marketed drugs from 265 examined were found to be cytochrome P450 inducers, and 83 were found to be suppressors. The value of this new information is illustrated with a more detailed examination of the DDI between PPARalpha agonists and HMG-CoA reductase inhibitors. This paper proposes that the well-documented, but poorly understood, increase in incidence of rhabdomyolysis when a PPARalpha agonist is co-administered with a HMG-CoA reductase inhibitor is at least in part the result of PPARalpha-induced general suppression of drug metabolism enzymes in liver. The authors believe this type of information will provide insights to other poorly understood DDI questions and stimulate further laboratory and clinical investigations on xenobiotic-mediated induction and suppression of drug metabolism.

A comparative review of apomorphine formulations for erectile dysfunction : recommendations for use in the elderly

Erectile dysfunction (ED) is a common medical condition that affects the sexual life of millions of men worldwide. First-line oral therapy for ED includes the use of phosphodiesterase type 5 inhibitors (sildenafil, tadalafil and vardenafil) and sublingual apomorphine. Apomorphine is a dopamine D(1) and D(2) receptor agonist that has been approved for marketing in Europe. Different apomorphine formulations have been tested, such as sublingual, subcutaneous and intranasal. However, the sublingual formulation has shown the best results in terms of efficacy, safety and tolerability, especially the 2mg and 3mg doses. Although clinical studies of the efficacy and tolerability of apomorphine sublingual (SL) have included older patients, who are more likely to have ED, no study has specifically assessed the efficacy and tolerability of different doses of apomorphine SL in aging men. Therefore, a MEDLINE search was conducted from January 1987 to November 2005 to identify studies of the efficacy, safety (in particular cardiovascular safety) and tolerability of different apomorphine formulations and doses as treatments for ED in the subcohort of aging men. On the basis of the most recent peer-reviewed publications, the first part of this article critically evaluates data regarding the epidemiology of ED in the aging population. The second part of the article focuses on the mechanism of action and pharmacokinetics of apomorphine both in the general and the elderly population. Finally, a critical analysis of the efficacy and safety of different apomorphine formulations and doses for the treatment of ED is reported. Apomorphine represents a first-line oral treatment for ED. Available formulations include only sublingual administration. Few studies have assessed the efficacy and safety of apomorphine in the elderly population. However, in clinical practice, older patients with multiple vascular risk factors and systematic vascular damage show poor overall response to apomorphine SL for the treatment of ED.

Tadalafil in the treatment of erectile dysfunction; an overview of the clinical evidence

Prevalence and severity of erectile dysfunction (ED) increase with aging and are often associated with illnesses, like diabetes mellitus, heart disease, and hypertension, pathologically characterized by endothelial dysfunction and whose prevalence increases with age. The assumption that ED is mainly a neurovascular disease is supported by the evidence that specific phosphodiesterase type 5 (PDE5) inhibition produces an efficient erection in a wide range of ages and conditions. The availability of specific PDE5 inhibitors has enabled the development of effective treatment strategies, in this contest, tadalafil may be considered as the least "typical" PDE5 inhibitor. In clinical trials, tadalafil significantly enhanced, in patients of different ages, all efficacy outcomes across disease etiologies and severities. With an effectiveness lasting up to 36h, tadalafil allows patients to choose when to have sexual activities without the need to time it, showing positive feedback in terms of quality of life related to the treatment. Headache and dyspepsia were the most frequent side-effects of tadalafil, followed by back pain, nasal congestion, myalgia, and flushing, but the impact that long time action could have on effectiveness and safety is not yet entirely defined. The aim of this article is to critically review the available evidence from the tadalafil clinical research program and give the physician a rational approach for intervention in the treatment of ED and related diseases.

Cardiovascular system as a ‘core’ of sexual life

Erectile dysfunction is a common worldwide clinical problem with tens of thousands of new cases per year. It has been argued that erectile dysfunction, like cardiovascular disease and other age-related disorders can be attributed, at least in part, to such modifiable para-aging phenomena.

Mechanism-based inhibition of cytochrome P450 3A4 by therapeutic drugs

Consistent with its highest abundance in humans, cytochrome P450 (CYP) 3A is responsible for the metabolism of about 60% of currently known drugs. However, this unusual low substrate specificity also makes CYP3A4 susceptible to reversible or irreversible inhibition by a variety of drugs. Mechanism-based inhibition of CYP3A4 is characterised by nicotinamide adenine dinucleotide phosphate hydrogen (NADPH)-, time- and concentration-dependent enzyme inactivation, occurring when some drugs are converted by CYP isoenzymes to reactive metabolites capable of irreversibly binding covalently to CYP3A4. Approaches using in vitro, in silico and in vivo models can be used to study CYP3A4 inactivation by drugs. Human liver microsomes are always used to estimate inactivation kinetic parameters including the concentration required for half-maximal inactivation (K(I)) and the maximal rate of inactivation at saturation (k(inact)). Clinically important mechanism-based CYP3A4 inhibitors include antibacterials (e.g. clarithromycin, erythromycin and isoniazid), anticancer agents (e.g. tamoxifen and irinotecan), anti-HIV agents (e.g. ritonavir and delavirdine), antihypertensives (e.g. dihydralazine, verapamil and diltiazem), sex steroids and their receptor modulators (e.g. gestodene and raloxifene), and several herbal constituents (e.g. bergamottin and glabridin). Drugs inactivating CYP3A4 often possess several common moieties such as a tertiary amine function, furan ring, and acetylene function. It appears that the chemical properties of a drug critical to CYP3A4 inactivation include formation of reactive metabolites by CYP isoenzymes, preponderance of CYP inducers and P-glycoprotein (P-gp) substrate, and occurrence of clinically significant pharmacokinetic interactions with coadministered drugs. Compared with reversible inhibition of CYP3A4, mechanism-based inhibition of CYP3A4 more frequently cause pharmacokinetic-pharmacodynamic drug-drug interactions, as the inactivated CYP3A4 has to be replaced by newly synthesised CYP3A4 protein. The resultant drug interactions may lead to adverse drug effects, including some fatal events. For example, when aforementioned CYP3A4 inhibitors are coadministered with terfenadine, cisapride or astemizole (all CYP3A4 substrates), torsades de pointes (a life-threatening ventricular arrhythmia associated with QT prolongation) may occur.However, predicting drug-drug interactions involving CYP3A4 inactivation is difficult, since the clinical outcomes depend on a number of factors that are associated with drugs and patients. The apparent pharmacokinetic effect of a mechanism-based inhibitor of CYP3A4 would be a function of its K(I), k(inact) and partition ratio and the zero-order synthesis rate of new or replacement enzyme. The inactivators for CYP3A4 can be inducers and P-gp substrates/inhibitors, confounding in vitro-in vivo extrapolation. The clinical significance of CYP3A inhibition for drug safety and efficacy warrants closer understanding of the mechanisms for each inhibitor. Furthermore, such inactivation may be exploited for therapeutic gain in certain circumstances.

Drug bioactivation, covalent binding to target proteins and toxicity relevance

A number of therapeutic drugs with different structures and mechanisms of action have been reported to undergo metabolic activation by Phase I or Phase II drug-metabolizing enzymes. The bioactivation gives rise to reactive metabolites/intermediates, which readily confer covalent binding to various target proteins by nucleophilic substitution and/or Schiff's base mechanism. These drugs include analgesics (e.g., acetaminophen), antibacterial agents (e.g., sulfonamides and macrolide antibiotics), anticancer drugs (e.g., irinotecan), antiepileptic drugs (e.g., carbamazepine), anti-HIV agents (e.g., ritonavir), antipsychotics (e.g., clozapine), cardiovascular drugs (e.g., procainamide and hydralazine), immunosupressants (e.g., cyclosporine A), inhalational anesthetics (e.g., halothane), nonsteroidal anti-inflammatory drugs (NSAIDSs) (e.g., diclofenac), and steroids and their receptor modulators (e.g., estrogens and tamoxifen). Some herbal and dietary constituents are also bioactivated to reactive metabolites capable of binding covalently and inactivating cytochrome P450s (CYPs). A number of important target proteins of drugs have been identified by mass spectrometric techniques and proteomic approaches. The covalent binding and formation of drug-protein adducts are generally considered to be related to drug toxicity, and selective protein covalent binding by drug metabolites may lead to selective organ toxicity. However, the mechanisms involved in the protein adduct-induced toxicity are largely undefined, although it has been suggested that drug-protein adducts may cause toxicity either through impairing physiological functions of the modified proteins or through immune-mediated mechanisms. In addition, mechanism-based inhibition of CYPs may result in toxic drug-drug interactions. The clinical consequences of drug bioactivation and covalent binding to proteins are unpredictable, depending on many factors that are associated with the administered drugs and patients. Further studies using proteomic and genomic approaches with high throughput capacity are needed to identify the protein targets of reactive drug metabolites, and to elucidate the structure-activity relationships of drug's covalent binding to proteins and their clinical outcomes.

Aging and pathogenesis of erectile dysfunction

The prevalence and the severity of erectile dysfunction (ED) increase with advancing age; different pathogenetic factors could contribute to age-related ED. We studied organic, relational and intrapsychic components of ED as a function of patients' age in a consecutive series of 977 patients with ED, using the specifically designed structured interview SIEDY. A complete physical examination and a series of biochemical, hormonal, psychometric and penile vascular tests were also performed. Relational factors seems to be more relevant in patients aged over 60 y, while intrapsychic disturbances play a major role in younger subjects. Organic factors are the most important determinant of ED in all age groups, but their contribution is more important in older patients. In fact, basal and dynamic peak cavernosal velocity at Doppler ultrasound penile examination was reduced in older patients. Among hormonal factors, the body mass index-dependent reduction of testosterone in older patients does not seem to play a crucial role in the pathogenesis of ED. No significant correlation was observed between testosterone level and the severity of ED, although patients reporting hypoactive sexual desire showed significantly lower testosterone levels when compared with the rest of the sample. A better understanding of the relative contribution of age-related pathogenetic factors of ED could be of help in the design of appropriate therapeutic approaches.

Safety and Tolerability of Oral Erectile Dysfunction Treatments in the Elderly

Erectile dysfunction (ED) is a common medical condition that affects the sexual life of millions of men worldwide. It is generally accepted that sexual function tends to decline with aging, which is often associated with a higher prevalence of sexual problems, including ED and loss of libido. As the mean age of men seeking medical help for sexual dysfunction continues to increase, it is important to assess the safety and tolerability of currently available medical treatments in elderly men, who often share other co-morbidities that should be carefully evaluated when any type of ED therapy is considered. With this aim in mind, a MEDLINE search was conducted from 1 January 1998 to 31 May 2004 to identify studies assessing the efficacy, safety and tolerability of treatments for ED in the elderly. Particular care was taken to assess the cardiovascular safety of oral drugs for ED in this subset of patients, who often have multiple cardiovascular risk factors which contribute to a complicated clinical scenario. The most important conclusion of the paper is that the high efficacy, reliability, safety and tolerability of oral ED treatments makes them appropriate first-line therapies for elderly patients with ED.