‘Off-label’ drug use in sexual medicine treatment

Current and emerging treatment options for premature ejaculation

Premature ejaculation (PE) is a prevalent male sexual dysfunction. Current standard treatment regimens include behavioural therapies, topical anaesthetics, dapoxetine and other selective serotonin reuptake inhibitors (SSRIs). Most of the pharmacotherapeutic options target neurotransmitters (such as serotonin and oxytocin) that have a role in the ejaculation mechanism. However, these treatments are mildly effective and only provide a temporary delay in the ejaculation latency time, and PE recurs when the treatment is stopped. Thus, a treatment for PE is urgently needed and research is ongoing to find the ideal PE therapy. The efficacy and safety of topical anaesthetics and SSRIs in delaying ejaculation have been confirmed in many well-designed controlled trials. Both preclinical and clinical studies on new-generation SSRIs are ongoing. Moreover, promising results came from clinical trials in which the efficacy of on-demand PE therapies targeting neurotransmitters other than serotonin, such as α1-adrenoceptor antagonists and oxytocin antagonists, was assessed. Surgical intervention and neuromodulation have been proposed as potential treatment options for PE; however, current PE guidelines do not recommend these treatments owing to safety concerns.

Testosterona, desejo sexual e conflito de interesse: periódicos biomédicos como espaços privilegiados de expansão do mercado de medicamentos

Resumo Este artigo focaliza a articulação entre pesquisa biomédica e indústria farmacêutica com base nos estudos da tecnociência. Abordamos o caso do medicamento Intrinsa – adesivo de testosterona, cujo propósito é o aumento do desejo sexual em mulheres – examinando artigos que relatam resultados de ensaios clínicos, publicados em periódicos científicos. Buscamos demonstrar como a população visada pelos ensaios clínicos foi paulatinamente expandida de modo a englobar um número cada vez maior de mulheres, o que pressupôs rearranjos na maneira de definir as disfunções para as quais o medicamento seria indicado e as possíveis causas subjacentes. Foi possível identificar três caminhos de ampliação do mercado para o Intrinsa: o primeiro baseou-se na alteração do status de menopausa. A terapia com testosterona passou a ser vinculada também ao envelhecimento (incluindo, portanto, a pré-menopausa e a menopausa “natural”) e não mais exclusivamente à menopausa cirúrgica; o segundo focalizou a dissociação entre o uso do Intrinsa e a terapia com estrógenos; o terceiro buscou vincular o medicamento ao aumento de “bem-estar”.

SLC6 neurotransmitter transporters: structure, function, and regulation

The neurotransmitter transporters (NTTs) belonging to the solute carrier 6 (SLC6) gene family (also referred to as the neurotransmitter-sodium-symporter family or Na(+)/Cl(-)-dependent transporters) comprise a group of nine sodium- and chloride-dependent plasma membrane transporters for the monoamine neurotransmitters serotonin (5-hydroxytryptamine), dopamine, and norepinephrine, and the amino acid neurotransmitters GABA and glycine. The SLC6 NTTs are widely expressed in the mammalian brain and play an essential role in regulating neurotransmitter signaling and homeostasis by mediating uptake of released neurotransmitters from the extracellular space into neurons and glial cells. The transporters are targets for a wide range of therapeutic drugs used in treatment of psychiatric diseases, including major depression, anxiety disorders, attention deficit hyperactivity disorder and epilepsy. Furthermore, psychostimulants such as cocaine and amphetamines have the SLC6 NTTs as primary targets. Beginning with the determination of a high-resolution structure of a prokaryotic homolog of the mammalian SLC6 transporters in 2005, the understanding of the molecular structure, function, and pharmacology of these proteins has advanced rapidly. Furthermore, intensive efforts have been directed toward understanding the molecular and cellular mechanisms involved in regulation of the activity of this important class of transporters, leading to new methodological developments and important insights. This review provides an update of these advances and their implications for the current understanding of the SLC6 NTTs.

Yohimbine relaxes the human corpus cavernosum through a non-adrenergic mechanism involving the activation of K+ATP-dependent channels

The mechanism by which yohimbine relaxes the human corpus cavernosum remains unclear. Using the human corpus cavernosum strips immersed in isometric baths containing Krebs-Henseleit solution, this study investigates the effect of yohimbine on the relaxation of the human corpus cavernosum through nitrergic pathways involving the activation of ATP-dependent potassium channels (K(ATP)). The maximal relaxation induced by yohimbine in the human corpus cavernosum strips pre-contracted with phenylephrine was 100+/-0% and only 30.5+/-5.0% when they were pre-contracted with 60-mM potassium (K(+)) solution. The maximal relaxation induced by yohimbine in phenylephrine pre-contracted tissues was significantly inhibited by tetrodotoxin, 1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or 7-nitroindazole (43.6, 36.1 and 42.6%, respectively). Neither the combination charybdotoxin-apamin nor tetraethylammonium altered the response of the human corpora cavernosa strips to yohimbine. Nevertheless, glibenclamide decreased the maximum relaxant response to yohimbine by 29.8% (P<0.05; n=12). The results suggest that yohimbine relaxes the human corpus cavernosum by a non-adrenergic, non-cholinergic mechanism, probably activating the nitrergic-soluble guanylate cyclase (NO-sGc) pathway and K(ATP).