Paroxetine is an oral drug that is designed to fight depression. Technically, it is a selective serotonin reuptake inhibitor (SSRI), a neurotransmitter involved in generating positive moods; however, paroxetine is better known for a very different reason.

Because of its history, it was popularized to treat a class of anxiety known as social anxiety disorder or social phobia, which at the time was interpreted as a sign of extreme shyness, and so it is known as the anti-shyness drug.

The history of paroxetine

Paroxetine was launched in 1992 by the American pharmaceutical giant GlaxoSmithKline (GSK) under the trade name Paxil . Its sales were much lower than other antidepressant drugs such as Prozac or Zoloft, so the company devised a powerful advertising campaign in 1999 to change this.

Advertising focused on a different use for paroxetine. The company was in charge of publicizing a new type of anxiety that was beginning to be studied, known as social anxiety disorder , which they associated with those people who show shyness. This was because his drug was the only one on the market that was clinically proven to treat this kind of anxiety.

Thanks to this, their sales improved with respect to previous years; transforming paroxetine into the “anti-shyness” drug proved to be very profitable .

The advertising campaign controversy

Today we know that social phobia is generated in shy people, but not all shy people have this kind of anxiety. Shyness is not a disorder , but a personality trait, and can be overcome by following some guidelines, without any need for medication.

The controversy of the story basically has to do with the advertising campaign for paroxetine, which incites the debate on how far the pharmaceutical industry is capable of making profits from its products, in this case “popularizing” an anxiety disorder that was beginning to be studied at the time, in its eagerness to outdo the competition … and despite the fact that this could generate confusion and stigmatization of people who, because of their personality, are shy .

The mechanism of action

Paroxetine is an antidepressant drug that acts on serotonin reuptake receptors, preventing their function to prolong the presence of the neurotransmitter in the synaptic space where it is released. In depression it has been seen that there are low levels of serotonin, a substance involved in the generation of positive states of mind , so by maintaining the little serotonin released helps to prolong its effects.

Furthermore, in in vitro studies of rat brains, the effect of paroxetine was found to be several times greater than that of sertraline (Zoloft) and significantly more potent than fluoxetine (Prozac) .

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Pharmacokinetics of the psychopharmaceutical

Paroxetine is administered orally in tablet, suspension (liquid) or capsule form, with complete absorption by our digestive system. Within the body, it is widely distributed, including in the CNS (it can pass the blood-brain barrier), where it will bind to the serotonin-catching receptors of neurons .

The half-life of the drug in an adult’s body is 21 hours, a time that must be taken into account for interactions with other drugs. Paroxetine is metabolised in the liver into various metabolites, none of which have been found to have an effect on the body, i.e. they are harmless.

It leaves the body mainly through the kidney (62%) in the form of urine, and the rest is excreted in the form of bile in the faeces. For these reasons, and as is the case with many medications, it is not advisable to be treated with this drug if you suffer from liver or kidney failure .

Therapeutic indications

Paroxetine is indicated to treat mainly the episodes of major depression, especially when other SSRI-type antidepressants have not been effective, as this drug has been found to be more potent than others in its class. Other uses in treatment are as follows:

  • Obsessive-compulsive disorder
  • Anxiety disorder with or without agoraphobia
  • Social anxiety disorder or social phobia
  • Panic disorder.
  • Post-Traumatic Stress Disorder.

Also there is a variety of paroxetine capsules, under the trade name of Brisdelle , which is used as a non-hormonal remedy to treat hot flashes in women going through menopause. In the latter case, the mechanism that the drug uses to prevent hot flashes is not known.

Side effects of paroxetine

Treatment with paroxetine can cause adverse reactions, as can the vast majority of drugs. As it is a substance that works on such an important messenger as serotonin, its list of side effects is quite long :

  • Increased cholesterol levels, decreased appetite
  • Sleepiness, insomnia, aggression, abnormal dreams.
  • Decreased concentration, dizziness, tremors, headache.
  • Blurred vision.
  • Nausea, constipation, diarrhea, dry mouth.
  • Sweating.
  • Sexual dysfunction.
  • Asthenia, weight gain.

It should be noted that during the clinical trials of this drug it was observed that in short trials carried out in children and adolescents , suicidal, self-injurious and hostile behaviour was increased , and therefore it is not recommended for these ages.

Contraindications

The main contraindication for paroxetine (like all SSRIs) is that it cannot be taken with another Monoamine Oxidase Inhibitor (MAOI) type antidepressant.

The reason for this is that serotonin is degraded by the enzyme monoamine oxidase A. If the enzyme is deactivated, serotonin concentrations increase and can lead to serotoninergic syndrome, a clinical picture that can be fatal. For this reason, you should always wait for a period between treatment with MAOIs and SSRIs.

Another contraindication of paroxetine consists of taking it together with another tricyclic antidepressant , since the drug inhibits the liver enzyme that is responsible for eliminating tricyclic antidepressants from the body. The effects of paroxetine on this enzyme can last for up to a week after treatment stops, so great care must be taken when changing drugs. The main adverse effect of this interaction is a symptom of toxicity, although in some cases sudden death has occurred.

Paroxetine is also not recommended in people who are hypersensitive to it, as well as if they have a history of mania. This is because all antidepressants can transform a depression into a mania in people who are predisposed to it.

In addition, treatment with this drug is totally prohibited in pregnant women , since it has been seen to generate malformations in the cardiovascular system of the fetus in its first months of development or various problems in the newborns if it was medicated during the last months of pregnancy with paroxetine. In terms of breastfeeding, in principle its excretion through the milk is minimal, but the child should be observed for safety.

Finally, the use of paroxetine may cause drowsiness or dizziness , as we have seen, so potentially dangerous activities, such as driving or operating heavy machinery, are not recommended.

Paroxetine and shyness

Paroxetine is an antidepressant that as part of a marketing campaign became popular in its use to help with the social anxiety disorder that some shy people suffer from, although it seems to have spread for use in overcoming shyness. Among the medical community, there is a debate about whether it really works or not .

Doctors who oppose the use of drugs to treat this type of anxiety maintain that current treatments do not generate any real change in the patient, that is, that after the medication is stopped, the anxiety returns. They have even seen a rebound effect, further increasing the anxiety they suffer when trying to socialise.

Another argument they rely on is the lack of knowledge of the long-term effects of the current drugs used for this purpose, as they are relatively new. Along with this, the long list of known side effects generated by paroxetine causes concern.