Philip Kell

The effect of sildenafil citrate (Viagra®) on visual sensitivity

The erectile dysfunction medicine sildenafil citrate (Viagra) inhibits phosphodiesterase type 6 (PDE6), an essential enzyme involved in the activation and modulation of the phototransduction cascade. Although Viagra might thus be expected to impair visual performance, reports of deficits following its ingestion have so far been largely inconclusive or anecdotal. Here, we adopt tests sensitive to the slowing of the visual response likely to result from the inhibition of PDE6. We measured temporal acuity (critical fusion frequency) and modulation sensitivity in four subjects before and after the ingestion of a 100-mg dose of Viagra under conditions chosen to isolate the responses of either their short-wavelength-sensitive (S-) cone photoreceptors or their long- and middle-wavelength-sensitive (L- and M-) cones. When vision was mediated by S-cones, all subjects exhibited some statistically significant losses in sensitivity, which varied from mild to moderate. The two individuals who showed the largest S-cone sensitivity losses also showed comparable losses when their vision was mediated by the L- and M-cones. Some of the losses appear to increase with frequency, which is broadly consistent with Viagra interfering with the ability of PDE6 to shorten the time over which the visual system integrates signals as the light level increases. However, others appear to represent a roughly frequency-independent attenuation of the visual signal, which might also be consistent with Viagra lengthening the integration time (because it has the effect of increasing the effectiveness of steady background lights), but such changes are also open to other interpretations. Even for the more affected observers, however, Viagra is unlikely to impair common visual tasks, except under conditions of reduced visibility when objects are already near visual threshold.

Medical management of sexual difficulties in HIV-positive individuals

In the current era of effective antiretroviral therapy, sexual dysfunction is being increasingly recognized in HIV-positive individuals. This article reviews the literature about the causes, treatments available and any issues specific to the HIV-positive individual.

An ethical dilemma: erectile dysfunction in the HIV-positive patient: to treat or not to treat.

Healthcare professionals are encountering an increasing number of HIV-positive male patients who seek medical help for erectile dysfunction (ED). The convergence of three factors contribute to this phenomenon: (1) high rates of new infection despite public health efforts, (2) the availability of noninvasive treatments for ED and (3) the emergence of highly effective anti-retroviral treatment which has transformed HIV disease from a terminal condition into a chronic disease. As patients are living longer and feeling better for longer periods, their interests understandably include development and maintenance of sexual relationships. Physicians whose patients request treatment for ED will face a dilemma. How should one balance obligations to the patient with concerns about potential risks to his sexual partner or partners? Easy answers are suspect. A doctorwith high regard for himself or herself as a judge of character will likely adopt a practice of case-by-case determination. Another doctor, more sceptical about the capacity of any of us to tell who will be sexually responsible, may adopt a rule of denying prescriptions to all but the rare person. This physician might cite striking and perhaps numerous examples, from personal experience or the testimony of others, of men widely thought to be paragons of responsibility who surreptitiously acted otherwise and lied about it to everyone, including their physicians. Still other practitioners will conclude that their responsibility for persons other than their patients is a concern only when the threat is immediate and clear. They will adopt the stance that their duty to protect others is discharged when they routinely discuss safer sexual practices with patients to whom they prescribe treatment for ED. This stance would be backed by many members of the public who maintain that everyone should protect themselves against the possibility of a sexually transmitted infection at all times. Most physicians will want to review a variety of considerations before adopting a position. Ideally, HIV-seropositive patients, before receiving any such therapies, should be counselled regarding a variety of medical and social issues. A wide range of information should be provided. These include safer-sex precautions, HIV-related disclosure practices (particularly regarding the relation with casual sexual partners), and parenting issues. Speci® cally, the possibility of infecting the partner, and subsequently, in a heterosexual relationship an unborn child, should be discussed1. This article addresses ethical and legal considerations relevant to the treatment of ED in HIVseropositive males.

The provision of sexual dysfunction services by genitourinary medicine physicians in the UK, 1999

Over 85% of clinical directors of genitourinary (GU) clinics in Britain support the provision of services for patients with sexual dysfunction in their clinics. However only 41% of those who support this provision are able to at present. The major barriers are a lack of resources and a lack of suitable training options for both medical and nursing staff. The Medical Society for the Study of Venereal Diseases (MSSVD) Special Interest Group (SIG) will be running a series of national meetings later this year in order to overcome the latter of these. Those clinics who are providing a service are offering a wider range of treatments than in 1997. As previously noted the services are still predominantly consultant and/or nurse led with junior medical staff having minimal involvement.

How do clients access their HIV test results from genitourinary medicine services in the UK? A time for change!

With the changes in the nations sexual health needs and the introduction of the Governments Sexual Health Strategy, GU services need to review their operational policies to accommodate the inevitable increase for service. There had been a long-standing practice of anyone having an HIV test to return in person to collect his or her result. As more and more people, many of whom are considered to be low risk, are testing for HIV as part of a routine sexual health check-up, the question is, do they really need to return in person for these results? The national survey shows that while the majority of clinics are insisting that everyone having an HIV test returns in person, there are some services that have already adopted other approaches. It is also evident that many service providers are also considering a change in policy.

Who should look after patients with sexual dysfunction? Why genitourinary physicians are ideally placed

Sexual dysfunction can be de® ned as the consistent inability to perform sexual activities to the satisfaction of the patient and/or their partner. Over the last 10 years there have been major breakthroughs regarding the physiology of sexual excitation and subsequent to these discoveries major new therapies have been developed especially for male erectile dysfunction (MED). The availability of an effective oral agent for MED has led to an unprecedented media coverage of sexual dysfunction. This has heightened public expectations and has led to more patients than ever before presenting with sexual dysfunction, but where can they go for help? Patients with sexual dysfunction often feel isolated and unsure of where to turn to for help. A glance at the advertisements in the tabloid newspapers will readily show the potential exploitation of patients with sexual dysfunction. Dubious services and exaggerated claims of cure abound to mislead patients, lure them into a sense of false hope and relieve them of their money rather than their sexual problems. Historically, professional services for these patients have been fragmented and inadequate. Many such services have been psychologically orientated on the premise that if there is something wrong with your sexual functioning the primary problem must be in your head. Indeed Masters and Johnson wrote `...the incidence of primary phy

Viagra slows the visual response to flicker

As an undesirable side effect, sildenafil citrate (Viagra) partially inhibits the phosphodiesterase PDE6 [1], which plays an essential role in phototransduction (reviewed in [2,3]). PDE6 not only activates the visual transduction cascade, but also controls the time over which the visual response is integrated, thereby helping to maintain the size of the visual response within an optimal range as the light level is increased [4]. Consistent with an increase in temporal integration following Viagra ingestion, performance improvements have been reported for an identification task that relies on the integration of two temporally separated stimuli [5].

The metabolic syndrome in HIV-seropositive patients

protein (pmpH gene) in the L-type serovars. The assay requires about two hours from sample processing to completion, and is capable of testing approximately 30 specimens simultaneously. Out of 86 specimens tested, none (0.0%, 95% confidence interval [CI] 0.0–4.2%) showed presence of the L-type serovars of C. trachomatis. There are a handful of potential causes for our null finding. The two most likely causes are the absence of LGV and the use of urogenital specimens. Though there has been a case report of urethritis associated with LGV serotypes, large surveillance trials in Europe have not found LGV among chlamydia-positive urogenital specimens. Unfortunately, rectal specimens were not collected as part of this study. However, an important finding of our study is that surveillance for LGV by molecular methods is a feasible exercise in settings where realtime PCR is available. The addition of this technique, applied to known chlamydiapositive rectal specimens, could vastly enhance LGV surveillance. Better estimates of LGV prevalence in Latin America and elsewhere in the developing world are crucial for the public health response to the disease. Such information is indicated to identify risk factors, classify high-risk populations and direct proper treatment of proctitis. Historically, LGV surveillance has relied on genotypic sequencing, an expensive and timely enterprise. However, the use of molecular methods to help differentiate between chlamydia serotypes makes such estimates possible in a wider range of settings and should be incorporated into surveillance programmes.

Lone circinate balanitis and genital keratoderma: underdiagnosed presentations of chlamydia infection in men?

Objectives To describe the experience in a genito‐urinary clinic of lone circinate balanitis and genital keratoderma.

Apomorphine SL in the treatment of erectile dysfunction

Men with erectile dysfunction (ED) have a high incidence of comorbid cardiovascular disease and diabetes. Additionally, some drugs used to treat cardiovascular disease have been implicated as contributors to ED. Sublingual (SL) apomorphine (Uprima®), a compound with D2-like dopamine receptor agonist effects, has a rapid onset of action, resulting in erectile response within 10 minutes of dosing in some patients (median onset of effect is 18—19 minutes). Apomorphine SL improves erectile function in men with mild-to-moderate ED and is well tolerated in patients with diabetes and/or cardiovascular disease.