Dapoxetine, sold under the brand name Priligy among others, is a selective serotonin reuptake inhibitor (SSRI) used for the treatment of premature ejaculation (PE) in men ages 18 to 64 years old. Dapoxetine works by inhibiting the serotonin transporter, increasing serotonin's action at the postsynaptic cleft, and as a consequence promoting ejaculatory delay. As a member of the SSRI family, dapoxetine was initially created as an antidepressant. However, unlike other SSRIs, dapoxetine is absorbed and eliminated rapidly in the body. Its fast-acting property makes it suitable for the treatment of PE, but not as an antidepressant. Originally created by Eli Lilly pharmaceutical company, dapoxetine was sold to Johnson & Johnson in 2003 and submitted as a New Drug Application to the US Food and Drug Administration (FDA) for the treatment of PE in 2004. Dapoxetine is sold in several European and Asian countries, and in Mexico. In the US, dapoxetine has been in phase III development. In May 2012, US-based Furiex Pharmaceuticals reached an agreement with ALZA Corp and Janssen Pharmaceuticals to market dapoxetine in the United States, Japan, and Canada, while selling the rights to market the drug in Europe, most of Asia, Africa, Latin America, and the Middle East to Menarini.
Medical uses
Premature ejaculation Randomized, double-blind, placebo-controlled trials have confirmed the efficacy of dapoxetine for the treatment of PE. Different dosages have different impacts on different types of PE. Dapoxetine 60 mg significantly improves the mean intravaginal ejaculation latency time (IELT) compared to that of dapoxetine 30 mg in men with lifelong PE, but no difference is seen in men with acquired PE. Dapoxetine, given 1–3 hours before sexual episode, prolongs IELT and increases the sense of control and sexual satisfaction in men of 18 to 64 years of age with PE. Since PE is associated with personal distress and interrelationship difficulty, dapoxetine provides help for men with PE to overcome this condition. With no drug approved specifically for treatment for PE in the US and some other countries, other SSRIs such as fluoxetine, paroxetine, sertraline, fluvoxamine, and citalopram have been used off-label to treat PE. Waldinger's meta-analysis shows that the use of these conventional antidepressants increases IELT two- to nine-fold above baseline, compared to three- to eight-fold when dapoxetine is used. However, these SSRIs may need to be taken daily to achieve meaningful efficacy, and their comparatively longer half-lives increase the risk of drug accumulation and a corresponding increase of adverse effects such as reduced libido. Dapoxetine, though, is generally categorized as a fast-acting SSRI. It is more rapidly absorbed and mostly eliminated from the body within a few hours. These pharmacokinetics are more favorable in that they might minimize drug accumulation in the body, habituation, and side effects.
Depression and anxiety Dapoxetine was initially considered unsuccessful in its intended use as an antidepressant; however, it has since been investigated as a possible aid to an approach to depression treatment focused on stress reduction, based on an animal model of depression.
Contraindications Dapoxetine should not be used in men with moderate to severe hepatic impairment and in those receiving CYP3A4 inhibitors such as ketoconazole, ritonavir, and telithromycin. Dapoxetine also cannot be used in patients with heart failure, permanent pacemaker, or other significant ischemic heart disease. Caution is advised in men receiving thioridazine, monoamine oxidase inhibitors, SSRIs, serotonin-norepinephrine reuptake inhibitors, or tricyclic antidepressants. If a patient stops taking one of these drugs, he should wait for 14 days before taking dapoxetine. If a patient stops taking dapoxetine, he should wait for 7 days before receiving these drugs.
Adverse effects The most common effects when taking dapoxetine are nausea, dizziness, dry mouth, headache, diarrhea, and insomnia. Discontinuation rates due to adverse effects and costs are very high, as demonstrated in a study in Asia which showed that cumulative discontinuation rates within one year are as high as 87%. Unlike other SSRIs used to treat depression, which have been associated with high incidences of sexual dysfunction, dapoxetine is associated with low rates of sexual dysfunction. Taken as needed, dapoxetine has very mild adverse effects of decreased libido (<1%) and erectile dysfunction (<4%).
Overdose No case of drug overdose has been reported during clinical trials.
Interactions
Phosphodiesterase 5 inhibitors Many men who have PE also suffer from erectile dysfunction (ED). Treatment for these patients should consider the drug–drug interaction between dapoxetine and PDE5 inhibitors such as tadalafil (Cialis) or sildenafil (Viagra). In Dresser study (2006), plasma concentration of 24 subjects was obtained. Half of the sample pool were treated with dapoxetine 60 mg plus tadalafil 20 mg; the other half were treated with dapoxetine 60 mg plus sildenafil 100 mg. These plasma samples were then analyzed using liquid chromatography-tandem mass spectrometry. The results showed that dapoxetine does not alter the pharmacokinetics of tadalafil or sildenafil.
Alcohol Alcohol does not affect the pharmacokinetics of dapoxetine when taking concurrently.
Pharmacology
Mechanism of action The mechanism through which dapoxetine affects premature ejaculation is still unclear, but dapoxetine is presumed to work by inhibiting serotonin transporter (SERT) and subsequently increasing serotonin's action at pre- and postsynaptic receptors. Human ejaculation is regulated by various areas in the central nervous system (CNS). The ejaculatory pathway originates from spinal reflex at the thoracolumbar and lumbosacral level of spinal cord activated by stimuli from male genitalia. These signals are passed on to the brain stem, which then is influenced by a number of nuclei in the brain such as medial preoptic and paraventricular nuclei. Clement's study performed on anaesthetized male rats showed that acute administration of dapoxetine inhibits ejaculatory expulsion reflex at supraspinal level by modulating activity of lateral paragigantocellular nucleus (LPGi) neurons. These effects cause an increase in pudendal motoneuron reflex discharge (PMRD) latency, though whether dapoxetine acts directly on LPGi or on the descending pathway in which LPGi located is unclear.
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