Paroxetine : All You Need To Know About | Pharmacology


Whenever it comes to talk about anti-depressants, you can’t avoid Paroxetine drug. Paroxetine is a class of drug that is used for the treatment of psychological disorders. Today we will discuss about this drug and will know it’s general pharmacology, uses, side effects, indications, contraindications, mechanism of action, dosages, interactions, toxicity, adverse effects, brand names etc. in detail.


Paroxetine is an anti depressants medicine that belongs to a class of anti-depressants drugs known as SSRI ( selective serotonin reuptake inhibitors ). This drug is also known as paroxetine hydrochloride. In addition it is similar to fluoxetine drug, works similar to fluoxetine and have same class. Paroxitine due to being a schedule H drug, it is sold only on the recommendation of a doctor. For this reason you can’t get this without the prescription of the Doctor. Secondly it is available in two strength lower strength and higher strength.

mental illness caused by depression


Paroxetine is used for psychological problems like mental illness which includes the following :

  • Depression the disease of mood swings
  • Obsessive compulsive disorder ( OCD )- disorder of forgetting of routine works and habits specifically.
  • Anxiety- Both GAD ( generalized anxiety disorder) & SAD ( socialized anxiety disorder ) especially
  • Post traumatic stress – stress developed due to traumatic injury after completion of the treatment
  • Premenstrual dysphoric disorder- a disorder in women on the onset of menopause in which mood swings, irritability, irregular vaginal discharge, sleep disturbances specifically occurs.
  • Hot flashes due to menopause
  • Premature ejaculation in males
  • Panic disorders includes fear of any attack even if there is nothing to worry

Lower strength

  • 7.5 mg
  • 12.5 mg
  • 25 mg
  • 37.5 mg

Higher strength

  • 10 mg
  • 20 mg
  • 30 mg
  • 40 mg

Side effects ( Common )

  • Constipation
  • Diarrhoea ( loose motions )
  • Insomnia ( sleeping disorder )
  • Headache ( cluster headache is common )
  • Dizziness ( Unconsciousness )
  • Drowsiness ( feeling of tired and sleepy )
  • Erectile dysfunction ( penile dysfunction )
  • Delayed ejaculation in males
  • Decrease libido ( loss of interest in sex )

Side effects ( Rare )

  • Blur vision
  • Impotency – inability to make a woman pregnant
  • Loss of appetite
  • Excess dreaming
  • Excess yawning
  • Suicidal thoughts
  • Serotonin syndrome
  • Change in sex drive or sexual functions


Although the dose of paroxetine depends on the age and the severity of disease and also vary from person to person. Certainly I don’t suggest you to take dose of paroxetine on my advice. Some other drugs also given to the patient in combination with paroxetine for better recovery of patient. As i have said I am suggesting only general dosage here. Always consult your doctor first before take any medicine.

1. Dose for depression

A). High dose : Evidently initial dose 20 mg is given to the patient after the meal at night and extended this upto 50 mg in divided doses and make it stable.

2. Dose for premenstrual dysphoric disorder

B). Low dose : Eventually initial dose 7.5 mg or 12.5 mg is given to the patient daily after the meal for mental therapy and make it stable.

3. Pediatric dose

5-10 mg oral once a day, maximum dose 20 mg per day for children more than 5 years old.

Dosage forms

Paroxetine is available in the following forms. Patient should not destroy these forms in order to get maximum desirable pharmacological effects of the drug. If you crush, break, bite it, surprisingly you won’t get the satisfactory results. Generally Paroxetine forms are :

  • Delayed sustained release form ( DSR )
  • Prolonged release form ( PR )
  • Control release ( CR )
  • Immediate release form ( IR )
  • Sustain release form ( SR )
  • Film coated form

Mechanism of action

Before start with how paroxetine ( SSRI ) works. Let’s understand the normal physiology of the serotonin. We know our brain makes some neurotransmitters such as Serotonin, Norepinephrine, Dopamine etc. All of them protect us from mental illness. Serotonin is especially known as happy hormone. It is made up by a long process of tryptophan ( an amino acid ). In a normal individual serotonin is produced in the brain. It is stored in the vesicles located in the presynaptic neuron. When an impulse ( electrical signal ) pass through these vesicles, the stored serotonin start releasing with the impulse and reach to the synaptic area ( space between presynaptic and postsynaptic neurone ). Further there are some channels present on the surface of the presynaptic neuron. Their function is to reabsorb ( reuptake ) the excess serotonin level. To balance the serotonin level in the synaptic area. So this is the normal physiology of serotonin in the brain.

On the other hand, in the depression, the amount of serotonin is less or not sufficient for the normal process. When serotonin comes in the synaptic area, the SSRI ( paroxetine ) doesn’t let the serotonin to go back to the vesicles and blocks the reuptake channels. Hence the serotonin stays in the synaptic area in order to fulfill the requirements.


Precautions ( contraindications )

Once you have taken the paroxetine dose, you must avoid such activities and actions:

  • Avoid driving
  • Don’t operate heavy machines
  • Avoid dose in pregnancy and breast feeding mother
  • Kidney problem
  • Heart problem
  • Liver problem
  • Epilepsy
  • Diabetes
  • Glaucoma
  • Several episodes of mania
  • History of bleeding disorder


Stop paroxetine if experience

  • Feeling agitation ( significantly more common )
  • Sudden mood swings
  • Chronic depression
  • Suicidal thoughts

Taper off of paroxetine

Generally Taper off means the withdrawal or leaving of drug that you were taking to recover from a disease. In short if anybody was taking paroxetine and now he /she has completely recovered and wants to taper off the paroxetine suddenly, you must tell your doctor first. In any event don’t try to withdraw from paroxetine yourself. If you do so you may experience some withdrawal symptoms such as :

  • Restlessness
  • Insomnia
  • Nervousness
  • Excess anger
  • Distraction

Interactions of paroxetine

Interaction means when a drug is given to a patient and the patient is already taking another medicines for another disease, the present drug that the doctor prescribes may show it’s pharmacological effects abnormally ( either increase or decrease ). Kindly tell your doctor before taking paroxetine if you are taking already any one of the following. By all means below is the list of medicines that interact with paroxetine.

  • Warfarin / Aspirine – Blood thinner
  • Olanzepine / Quetiapine – Psychological medicine
  • Phenobarbitone / Phenytoin – Anti conversant medicine
  • Lorazepam / Diazepam – UTI medicine
  • Frusemide – Sleeping medicine
  • Amiodarone – Heart disease medicine
  • HIV medicine
  • Theophylline – respiratory medicine
  • Analgesics & anti-inflammatory
  • Anti-epileptic drugs
  • Antivirals
  • Anaesthetics
paroxetine structure

Toxicity of paroxetine

If a person takes paroxetine for longer duration. And without the recommendation of the doctor. And that to more than the recommended dose, he / she may have life-threatening conditions called serotonin syndrome. The serotonin syndrome may be developed either due to interaction of other drugs or due to overdoses that may lead to the following symptoms.

  • Tremor
  • Agitation
  • Exaggerated reflexes ( hyperreflexia )
  • Rhythmic muscle spasm ( clonus )
  • Fever over 39°C / 102.2°F
  • Hypertonia
  • Seizures
  • Diaphoresis
  • Diarrhea
  • Hyperthermia

If above symptoms are left untreated it will lead to muscle breakdown. Then further will lead coma and thereafter death of the patient.

Treatment of paroxetine toxicity

  • Discontinuation of current medicines undoubtedly
  • Use specifically benzodiazepines if patient feels agitation
  • If symptoms still persist use cyproheptadine

Popular brands

  • Paxil
  • Pari 20
  • Xet 20
  • Pexep CR – 37.5 mg
  • Seroxat CR

Price per tablet in INR

StrengthPrice ( in INR )
12.5 mg16.80
25 mg22.60
37.5 mg32.70
10 mg15.70
20 mg20.30
30 mg26.50
40 mg34.40

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