Paxil (Paroxetine). Dosage, Side Effects, Interactions
Paxil (Paroxetine) is one of the selective serotonin reuptake inhibitors and is used, among other things, to treat depression and obsessive-compulsive disorders.
Paxil (Paroxetine) belongs chemically to the drug group of selective serotonin reuptake inhibitors . It belongs to the antidepressants and psychoanaleptics. The active substance is used in the treatment of depression , obsessive-compulsive disorder, panic disorder with or without agoraphobia, social anxiety disorder/social phobia and generalized anxiety disorder
How Paxil (Paroxetine) works
Paroxetine is a selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitor into brain neurons. The active ingredient has only a low affinity for muscarinic cholinergic, alpha1/alpha2 and beta- adrenoceptors as well as for dopamine and histamine receptors.
After oral administration, paroxetine undergoes first-pass metabolism. After administration of higher single doses or after multiple administration, there can be a disproportionate increase in the absolute bioavailability of the active substance and consequently non-linear kinetics. However, this is usually only slightly pronounced.
Approximately 95% of paroxetine present in plasma is protein bound (in the therapeutic concentration range).
The elimination half-life is variable but is usually about one day.
Excretion is renal and via the bile with the faeces.
Dosage of Paxil (Paroxetine)
Paroxetine should be taken once a day, with breakfast in the morning. The film-coated tablet should be swallowed whole. The dosage of paroxetine depends on the clinical picture.
The recommended dose of active ingredient for depressive disorders is usually 20 mg per day. The dosage should be checked 3-4 weeks after the start of therapy and adjusted if necessary. The dose can be increased in 10 mg increments up to a maximum of 50 mg paroxetine per day.
obsessive compulsive disorder
The recommended dosage of paroxetine for treating OCD is 40 mg per day. You should start with 20 mg paroxetine per day and then gradually increase in 10 mg increments to the recommended dose. If 40 mg per day is not sufficient, it can be increased to a maximum dose of 60 mg per day.
The recommended dose of paroxetine for the treatment of panic disorders is 40 mg per day. The initial dose should start at 10 mg and then be increased in 10 mg increments up to the recommended dose. If necessary, the daily dose can be increased to a maximum of 60 mg paroxetine per day if there is no response.
Social anxiety disorder/social phobia
For the treatment of social anxiety disorder/social phobia, a dose of 20 mg per day of paroxetine is recommended. If necessary, this can be increased in 10 mg steps up to a maximum daily dose of 50 mg paroxetine.
Generalized Anxiety Disorder
A paroxetine dose of 20 mg per day is recommended for the treatment of generalized anxiety disorder. If this is not sufficient, it can be gradually increased in 10 mg steps up to 50 mg paroxetine per day.
Elderly people show increased paroxetine plasma levels. The starting dose should be chosen as described above, the maximum daily dose should not exceed 40 mg paroxetine per day.
children and young people
The active substance should not be used in children and adolescents, as studies have shown that they have an increased risk of suicidality. In addition, there is no adequate proof of effectiveness.
Kidney and liver damage
Patients with severe renal impairment (creatinine clearance <30ml/min) or hepatic insufficiency show increased paroxetine plasma concentrations. The dosage should therefore be chosen lower.
Discontinuation of paroxetine
Paroxetine should not be discontinued abruptly as withdrawal symptoms may occur. The following withdrawal symptoms may occur, among others:
- sensory disorders
- sleep disorders
- Agitation, confusion, emotional instability, irritability
The daily dose should be reduced slowly (in 10 mg increments) at weekly intervals. Should symptoms nevertheless occur, it can be considered to use the last used dose in order to then reduce it in smaller steps in consultation with the doctor treating you.
Side effects of Paxil (Paroxetine)
Therapy with paroxetine can lead to a variety of side effects. Below is a list according to the frequency of possible side effects.
- Difficulty concentrating
- sexual dysfunction.
- Increase in cholesterol levels
- decreased appetite
- unusual dreams (including nightmares)
- blurred vision
- constipation, diarrhea
- dry mouth
- states of weakness
- weight gain.
- Abnormal bleeding, especially of the skin and mucous membranes (ecchymosis)
- Altered blood sugar levels in diabetics
- confusional states
- extrapyramidal disorders
- sinus tachycardia
- Occasional rise or fall in blood pressure, orthostatic hypotension
- skin rash
- urinary retention
- urinary incontinence.
- Hyponatraemia (especially in elderly patients, sometimes in combination with the syndrome of inadequate ADH secretion)
- manic reactions
- Depersonalization/experience of alienation
- panic attacks
- Restless Legs Syndrome (RLS)
- Elevation of liver enzymes
- arthralgia, myalgia.
- Serious, possibly fatal, allergic reactions (including anaphylactoid reactions and Quincke’s edema)
- Syndrome of inappropriate ADH secretion
- Serotonin syndrome (especially when using other serotonergic and/or neuroleptic substances at the same time)
- acute glaucoma
- Gastrointestinal bleeding
- Liver disease (eg, hepatitis , liver failure)
- Serious adverse reactions (including erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis, phosensitivity syndrome)
- peripheral edema.
Side effects with unknown frequency
- Suicidal thoughts (especially in adolescents with depressive disorders, young adults between 18 and 24 years of age and adults with depressive disorders)
Paroxetine may interact with other substances in a number of ways.
The simultaneous intake of paroxetine and serotonergic substances (e.g. triptans , tramadol , linezolid , methylene blue , lithium , etc.) can lead to the occurrence of 5-HAT-associated effects (serotonin syndrome). The simultaneous use of paroxetine and MAO inhibitors is therefore contraindicated.
The concomitant use of pimozide and paroxetine is contraindicated due to the risk of QT prolongation.
Decreased paroxetine levels have been observed when fosamprenavir / ritonavir and paroxetine are taken concomitantly .
Taking pravastatin and paroxetine at the same time can increase blood sugar levels. The dosage of antidiabetics must be adjusted in diabetics.
Paroxetine leads to an increase in procyclidine levels when the two active substances are taken at the same time. If anticholinergic effects occur, the procyclidine dose must be reduced.
Inhibition of the CYP2D6 enzyme by paroxetine
Due to the inhibition of the CYP2D6 enzyme by paroxetine, it can lead to an increase in the plasma levels of concomitantly used medicinal products. This can happen, for example, with tricyclic antidepressants (e.g. clomipramine , nortriptyline ), phenothiazine neuroleptics (e.g. perphenazine ), risperidone , atomoxetine , certain type Ic antiarrhythmics (e.g. flecainide ), and metoprolol .
In addition, paroxetine-induced CYP2D6 inhibition may result in decreased plasma concentrations of a major tamoxifen active metabolite , endoxifene.
Alcohol should be avoided during treatment with paroxetine.
Concomitant treatment with paroxetine and oral anticoagulants may result in increased anticoagulation and a bleeding tendency. Therefore, paroxetine should be used with great caution in patients on oral anticoagulation.
Non-steroidal anti-inflammatory drugs, acetylsalicylic acid and other antiplatelet drugs
Simultaneous therapy with paroxetine and non-steroidal anti-inflammatory drugs (NSAIDs) or acetylsalicylic acid and other platelet aggregation inhibitors can lead to an increased tendency to bleed. Caution should also be exercised when paroxetine is administered concomitantly with medicinal products that affect platelet function or increase the risk of bleeding.
Paroxetine should not be used in the presence of hypersensitivity to the active ingredient or any component of the drug.
Simultaneous therapy with MAO inhibitors must not be carried out. There must be an interval of at least two weeks (for an irreversible MAOI) or 24 hours (for a reversible MAOI, including methylene blue) between paroxetine therapy and discontinuation of therapy with MAOIs. At least 1 week must elapse between stopping paroxetine and starting treatment with an MAOI.
Paroxetine should also not be taken in combination with thioridazine since paroxetine can increase plasma concentrations of thioridazine, which can lead to QT prolongation with consequent ventricular arrhythmias such as torsades de pointes and sudden death.
Paroxetine should also not be taken together with pimozide
Paroxetine should only be used during pregnancy if absolutely necessary. Some epidemiological studies indicate an increased risk of malformations, particularly of a cardiovascular nature, and the occurrence of primary pulmonary hypertension .
Small concentrations of paroxetine pass into breast milk. The serum concentration in breastfed infants was either undetectable or very low. Drug reactions in these children were not observed. According to the prescribing information, breastfeeding can therefore be considered.
As with all psychoactive medicinal products, patients treated with paroxetine should be cautioned that it may affect their ability to drive and use machines.
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