Selective Serotonin Reuptake Inhibitors (SSRIs) (Adverse effects)

Selective serotonin reuptake inhibitors (SSRIs) are a widely used type of antidepressant medication that share a same mechanism: inhibit the reuptake of serotonin (a neurotransmitter substance present in the brain causing alterations in diverse psychiatric disorders, among which is depression).

They are effective medicines and have a good safety profile with fewer effects on other neurotransmitters than other antidepressants, for this reason, they are called “selective”. This generally means fewer adverse effects and facilitates continuing the treatment.

The SSRIs metabolize (are eliminated) principally by the liver. The rate of speed that they need to do this varies with each person and can vary from 24 - 72 hours, in general terms. The main indications for SSRIs are:

  • Depressive disorder
  • Preventative treatment of relapses / recurrences of depression
  • Panic attack disorder with or without agoraphobia
  • Post traumatic stress disorder
  • Social anxiety disorder (social phobia)

Sexual Dysfunction

Between 20 and 70% of the persons who take selective serotonin reuptake inhibitors (SSRIs) experience the side effect of sexual dysfunction. As a side effect of SSRIs, it merits special mention given the characteristics of the problem.

The base disease for which treatment was prescribed (depression and other psychiatric disorders) can have repercussions on sexual function, making an evaluation of SSRIs as responsible agents difficult. Additionally, the frequency of having these side effects are probably underestimated, as not all patients mention this complication.

The most common effects include:

  • Low sex drive
  • Inability to ejaculate or delayed ejaculation
  • Difficulty achieving orgasm during sex
  • Anorgasmy (inability to achieve orgasm during sex)

Said effects can be linked to the prescribed drug itself as well as to the dose taken. Therefore, in some patients, there is an effort to alleviate the effects by reducing the dose or alternating the antidepressant. Likewise, in some cases, the patients builds up a tolerance to the drug and the sexual dysfunction symptoms appear transitorily; these symptoms tend to disappear or diminish once tolerance to the drug is developed.


  • Celexa®
  • Lexapro®
  • Prozac ®
  • Paxil ®
  • Zoloft ®


SSRIs are relatively safe antidepressant medicines that have few side effects. Among the drugs that comprise this group of anti-depressants, there is little difference in the frequency and severity of the side effects that may appear.

Some of the most frequent side effects of SSRIs are:

  • Digestive system: the adverse gastrointestinal effects are the greatest disadvantage of SSRIs: 20 - 25% of the patients treated with these drugs have nausea (generally transitory, and disappear weeks after having begun treatment) and less frequently, diarrhea.
  • Nervous system: between 1 and 3 persons out of 10 that receive SSRIs have adverse effects consisting of dry mouth and increased sweating. Some 10 - 25% also have insomnia, nervousness or headaches. Less frequently, suicidal thoughts and exceptionally motor symptoms similar to those of Parkinson's disease.
  • Cardiovascular system: less frequent effects that can include palpitations, fainting or blood pressure alterations (hypo- or hypertension).
  • Endocrine system: in some cases, anorexia although in others, weight gain. Menstrual cycle disorders and other hormonal disorders.
  • Less frequently: anorgasmy (lack of ability to have an orgasm), dysuria (burning pain while urinating) , paresthesia (pins-and-needles pain), skin rashes, mania, hyopmania, brusque mood changes, nervousness and extrapyramidal reactions, hyponatremia, withdrawal symptoms.


Despite the fact that SSRIs are safe and effective, they can interact with many other medicines. The SSRIs, the same as other classes of antidepressants and drugs that act on the nervous system, can alter the course of the illness if the patients has manic-depressive disorder; there should also be a rigorous control of the patients with mania or epilepsy. The latter tends to be manifested by swift ideation , not common, disproportional happiness or excessive physical activity, fewer hours of sleep and reduced feeling of fatigue. Precaution should be taken when driving a car or operating dangerous machinery

A treatment with MAOIs (monoamine oxidase inhibitors- another type of antidepressant medicines) should not begin until 2 weeks have passed after suspending SSRI treatment. Treatment should be suspended gradually, and abrupt suspension avoided, in case of the appearance of withdrawal symptoms. In addition, the risk of bone fractures in patients over 50 years of age that have received treatment for more than 5 years has increased.

Gene or region studied

  • 5-HT2A
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