How paroxetine works
The nerve cells in the brain communicate with each other via chemical messengers called neurotransmitters. These are released by one cell and “perceived” by the next via certain docking sites (receptors). The messenger substances are then taken up again by the first cell, which ends their effect.
In such cases, selective serotonin reuptake inhibitors (SSRIs) such as paroxetine can help: These antidepressants prevent the reuptake of serotonin into the cell of origin. This allows serotonin, once released, to act longer on the target cell – symptoms of serotonin deficiency such as depression and anxiety improve.
Uptake, degradation and excretion
The resulting metabolites have no antidepressant effect and are rapidly excreted. Excretion is very individual, with about one-third occurring in the stool and two-thirds in the urine. After one day, about half of the absorbed active substance has disappeared from the body.
When is paroxetine used?
Paroxetine is used to treat:
- depressive disorders
- Obsessive-compulsive disorders
- Panic disorders
- Social anxiety disorders (social phobia)
- Post-traumatic stress disorder
Generally, therapy is given over a longer period of time, and the benefits of therapy should be reviewed periodically.
How paroxetine is used
Most often, paroxetine is administered in tablet form. For patients with dysphagia or a feeding tube, there are liquid preparations such as drops or a suspension for oral administration.
It usually takes two to six weeks – depending on the area of application – until the desired effect is achieved.
To end the therapy, it is discussed with the doctor how to discontinue paroxetine. Sudden discontinuation is not advised because this can cause severe side effects and discontinuation symptoms. Instead, the drug is reduced very slowly (gradually), which is called “tapering” the therapy.
When taking the antidepressant, nausea and sexual dysfunction occur very often (in more than one in ten people treated).
Side effects such as drowsiness, insomnia, tremor, headache, blurred vision, yawning, sweating, weakness, and dizziness occur frequently (in one in ten to one in one hundred people treated). These side effects are also seen when paroxetine is stopped too quickly.
What should I be aware of when taking paroxetine?
Contraindications
Paroxetine must not be taken by:
- concomitant use of monoamine oxidase inhibitors (MAO inhibitors) – also antidepressants
- @ concomitant use of thioridazine and/or pimozide (antipsychotics) – antipsychotic agents
Drug interactions
Various active ingredients can inhibit or increase the breakdown of paroxetine via the liver. These include, in particular, pimozide (antipsychotic), fosamprenavir and ritonavir (HIV medications), procyclidine (anti-Parkinson’s medication), phenprocoumon (anticoagulant), and acetylsalicylic acid (analgesic and anticoagulant).
- Anti-arrhythmic agents (e.g., propafenone, flecainide)
- Beta-blockers (cardiovascular drug)
- Insulin (diabetes drug)
- Epilepsy medicines (e.g., carbamazepine, phenobarbital, phenytoin)
- Parkinson’s disease medication (e.g., levodopa, amantadine)
- Antipsychotics (e.g., risperidone, thioridazine)
- Other antidepressants (e.g., tricyclic antidepressants and selective-serotonin reuptake inhibitors)
- Tamoxifen (breast cancer treatment)
- Tramadol (pain reliever)
Age Limitation
A therapeutic benefit of paroxetine in children and adolescents under 18 years of age has not been reliably proven. Therefore, the drug should be used only after the age of 18 years.
Older patients may experience slower excretion of the antidepressant, so it may need to be dosed lower. The same applies in patients with renal or hepatic impairment.
Pregnancy and lactation
For this reason, paroxetine should be taken during pregnancy only if absolutely necessary. If possible, better studied substances (e.g., citalopram, sertraline) should be used.
Paroxetine passes into breast milk in small amounts. To date, no abnormalities have been observed in breastfed infants when the mother took the antidepressant. Paroxetine is therefore one of the SSRIs of choice in the breastfeeding period – along with citalopram and sertraline.
Paroxetine is available by prescription in Germany, Austria, and Switzerland in any dosage and dosage form and is only available in pharmacies.
Since when is paroxetine known?
Paroxetine was introduced to the market in the USA in 1992. Since the original manufacturer’s patent expired in 2003, numerous generics containing the active ingredient have come onto the market.