1. Name Of The Medicinal Product
Paroxetine 20 mg tablets
2. Qualitative And Quantitative Composition
Each tablet contains:
Paroxetine 20 mg equivalent to 22.21 mg Paroxetine hydrochloride
For excipients see section 6.1 “List of excipients”.
3. Pharmaceutical Form
Tablet
Diamond-shaped white to off-white tablets, deep score on one side, small score on the other side.
4. Clinical Particulars
4.1 Therapeutic Indications
Treatment of
- Major Depressive Episode
- Obsessive Compulsive Disorder
- Panic Disorder with and without agoraphobia
- Social Anxiety Disorders/Social phobia
- Generalised Anxiety Disorder
- Post-traumatic Stress Disorder
4.2 Posology And Method Of Administration
It is recommended that paroxetine is administered once daily in the morning with food.
The tablet should be swallowed rather than chewed.
MAJOR DEPRESSIVE EPISODE
The recommended dose is 20 mg daily. In general, improvement in patients starts after one week but may only become evident from the second week of therapy.
As with all antidepressant medicinal products, dosage should be reviewed and adjusted if necessary
within 3 to 4 weeks of initiation of therapy and thereafter as judged clinically appropriate. In some patients, with insufficient response to 20 mg, the dose may be increased gradually up to a maximum of 50 mg a day in 10 mg steps according to the patient's response.
Patients with depression should be treated for a sufficient period of at least 6 months to ensure that they are free from symptoms.
OBSESSIVE COMPULSIVE DISORDER
The recommended dose is 40 mg daily. Patients should start on 20 mg/day and the dose may be increased gradually in 10 mg increments to the recommended dose. If after some weeks on the recommended dose insufficient response is seen some patients may benefit from having their dose increased gradually up to a maximum of 60 mg/day.
Patients with OCD should be treated for a sufficient period to ensure that they are free from symptoms. This period may be several months or even longer. (see section 5.1 Pharmacodynamic Properties)
PANIC DISORDER
The recommended dose is 40 mg daily. Patients should be started on 10 mg/day and the dose gradually increased in 10 mg steps according to the patient's response up to the recommended dose. A low initial starting dose is recommended to minimise the potential worsening of panic symptomatology, which is generally recognised to occur early in the treatment of this disorder. If after some weeks on the recommended dose insufficient response is seen some patients may benefit from having their dose increased gradually up to a maximum of 60 mg/day.
Patients with panic disorder should be treated for a sufficient period to ensure that they are free from symptoms. This period may be several months or even longer (see section 5.1 Pharmacodynamic Properties)
SOCIAL ANXIETY DISORDER/SOCIAL PHOBIA
The recommended dose is 20 mg daily. If after some weeks on the recommended dose insufficient response is seen some patients may benefit from having their dose increased gradually in 10 mg steps up to a maximum of 50 mg/day. Long-term use should be regularly evaluated (see section 5.1 Pharmacodynamic Properties).
GENERALISED ANXIETY DISORDER
The recommended dose is 20 mg daily. If after some weeks on the recommended dose insufficient response is seen some patients may benefit from having their dose increased gradually in 10 mg steps up to a maximum of 50 mg/day. Long-term use should be regularly evaluated (see section 5.1 Pharmacodynamic Properties).
POST-TRAUMATIC STRESS DISORDER
The recommended dose is 20 mg daily. If after some weeks on the recommended dose insufficient response is seen some patients may benefit from having their dose increased gradually in 10 mg steps up to a maximum of 50 mg/day. Long-term use should be regularly evaluated (see section 5.1 Pharmacodynamic Properties).
GENERAL INFORMATION
WITHDRAWAL SYMPTOMS SEEN ON DISCONTINUATION OF PAROXETINE
Abrupt discontinuation should be avoided (see section 4.4 Special Warnings and Special Precautions for Use and section 4.8 Undesirable Effects). The taper phase regimen used in clinical trials involved decreasing the daily dose by 10 mg at weekly intervals. If intolerable symptoms occur following a decrease in the dose or upon discontinuation of treatment, then resuming the previously prescribed dose may be considered. Subsequently, the physician may continue decreasing the dose, but at a more gradual rate.
Special Populations:
• Elderly
Increased plasma concentrations of paroxetine occur in elderly subjects, but the range of concentrations overlaps with that observed in younger subjects. Dosing should commence at the adult starting dose. Increasing the dose might be useful in some patients, but the maximum dose should not exceed 40 mg daily.
• Children and adolescents (7-17 years)
Paroxetine should not be used for the treatment of children and adolescents as controlled clinical trials have found paroxetine to be associated with increased risk for suicidal behaviour and hostility. In addition, in these trials efficacy has not been adequately demonstrated (see section 4.4 Special Warnings and Special Precautions for use and section 4.8 Undesirable Effects).
• Children aged below 7 years
The use of paroxetine has not been studied in children less than 7 years. Paroxetine should not be used, as long as safety and efficacy in this age group have not been established.
• Renal/hepatic impairment
Increased plasma concentrations of paroxetine occur in patients with severe renal impairment (creatinine clearance less than 30 ml/min) or in those with hepatic impairment. Therefore, dosage should be restricted to the lower end of the dosage range.
4.3 Contraindications
Known hypersensitivity to paroxetine or any of the excipients.
Paroxetine is contraindicated in combination with monoamine oxidase inhibitors (MAOIs). Treatment with paroxetine can be initiated:
- two weeks after discontinuation of an irreversible MAOI, or
- at least 24hrs after discontinuation of a reversible MAOI (e.g. moclobemide).
At least one week should elapse between discontinuation of paroxetine and initiation of therapy with any MAOI.
Paroxetine should not be used in combination with thioridazine, because, as with other drugs which inhibit the hepatic enzyme CYP450 2D6, paroxetine can elevate plasma levels of thioridazine (see section 4.5 Interactions with other medicinal products and other forms of interaction). Administration of thioridazine alone can lead to QTc interval prolongation with associated serious ventricular arrhythmia such as torsades de pointes, and sudden death
4.4 Special Warnings And Precautions For Use
Treatment with paroxetine should be initiated cautiously two weeks after terminating treatment with an irreversible MAOI or 24 hours after terminating treatment with a reversible MAO inhibitor. Dosage of paroxetine should be increased gradually until an optimal response is reached (see section 4.3 Contraindications and section 4.5 Interactions with other medicinal products and other forms of interaction).
Children and Adolescents (7-17 years)
Paroxetine should not be used in the treatment of children and adolescents under the age of 18 years. In clinical trials increased suicidal related behaviours (suicide attempts and suicidal thoughts) and hostility (predominantly aggression, oppositional behaviour and anger) were more frequently observed in children and adolescents treated with paroxetine compared to those treated with placebo. In addition, in these trials efficacy has not been adequately demonstrated and long-term safety data in children and adolescents concerning growth, maturation and cognitive and behavioural development are lacking (see section 4.8 Undesirable Effects).
Suicide/suicidal ideation
Depression is associated with an increased risk of suicidal thoughts, self harm and suicide. This risk persists until significant remission occurs. As improvement may not occur during the first few weeks or more of treatment, patients should be closely monitored until such improvement occurs. It is general clinical experience with all antidepressant therapies that the risk of suicide may increase in the early stages of recovery.
Other psychiatric conditions for which paroxetine is prescribed can also be associated with an increased risk of suicidal behaviour. In addition, these conditions may be co-morbid with major depressive disorder. The same precautions observed when treating patients with major depressive disorder should therefore be observed when treating patients with other psychiatric disorders.
Patients with a history of suicidal behaviour or thoughts, or those exhibiting a significant degree of suicidal ideation prior to commencement of treatment, are at a greater risk of suicidal thoughts or suicide attempts, and should receive careful monitoring during treatment.
There is a possibility of an increased risk of suicide related behaviour in young adults ages 18-29. Young adults should therefore be monitored carefully throughout treatment.
There are insufficient data concerning the risk of suicide related behaviour in treatment naïve patients, but careful monitoring might be warranted.
Patients, (and caregivers of patients) should be alerted about the need to monitor for the emergence of suicidal ideation/behaviour or thoughts of harming themselves and to seek medical advice immediately if these symptoms present.
Akathisia
The use of paroxetine has been associated with the development of akathisia, which is characterized by an inner sense of restlessness and psychomotor agitation such as an inability to sit or stand still usually associated with subjective distress. This is most likely to occur within the first few weeks of treatment. In patients who develop these symptoms, increasing the dose may be detrimental.
Serotonin Syndrome/Neuroleptic Malignant Syndrome
On rare occasions development of a serotonin syndrome or neuroleptic malignant syndrome-like events may occur in association with treatment of paroxetine, particularly when given in combination with other serotonergic and/or neuroleptic drugs. As these syndromes may result in potentially lifethreatening conditions, treatment with paroxetine should be discontinued if such events (characterized by clusters of symptoms such as hyperthermia, rigidity, myoclonus, autonomic instability with possible rapid fluctuations of vital signs, mental status changes including confusion, irritability, extreme agitation progressing to delirium and coma) occur and supportive symptomatic treatment should be initiated. Paroxetine should not be used in combination with serotonin-precursors (such as L-tryptophan, oxitriptan) due to the risk of serotonergic syndrome.
(See Sections 4.3 Contraindications and 4.5 Interactions with other medicinal products and other forms of interaction).
Mania
As with all antidepressants, paroxetine should be used with caution in patients with a history of mania. Paroxetine should be discontinued in any patient entering a manic phase.
Renal/hepatic impairment
Caution is recommended in patients with severe renal impairment or in those with hepatic impairment.
(see section 4.2 Posology and Method of Administration)
Diabetes
In patients with diabetes, treatment with an SSRI may alter glycaemic control. Insulin and/or oral hypoglycaemic dosage may need to be adjusted.
Epilepsy
As with other antidepressants, paroxetine should be used with caution in patients with epilepsy.
Seizures
Overall the incidence of seizures is less than 0.1% in patients treated with paroxetine. The drug should be discontinued in any patient who develops seizures.
ECT
There is little clinical experience of the concurrent administration of paroxetine with ECT.
Glaucoma
As with other SSRI's, paroxetine infrequently causes mydriasis and should be used with caution in patients with narrow angle glaucoma or history of glaucoma.
Cardiac Conditions
The usual precautions should be observed in patients with cardiac conditions.
Hyponatraemia
Hyponatraemia has been reported rarely, predominantly in the elderly. Caution should also be exercised in those patients at risk of hyponatraemia e.g. from concomitant medications and cirrhosis. The hyponatraemia generally reverses on discontinuation of paroxetine.
Haemorrhage
There have been reports of cutaneous bleeding abnormalities such as ecchymoses and purpura with SSRIs. Other haemorrhagic manifestations e.g. gastrointestinal haemorrhage have been reported. Elderly patients may be at an increased risk.
Caution is advised in patients taking SSRI's concomitantly with oral anticoagulants, drugs known to affect platelet function or other drugs that may increase risk of bleeding (e.g. atypical antipsychotics such as clozapine, phenothiazines, most TCA's, acetylsalicylic acid, NSAID's, COX-2 inhibitors) as well as in patients with a history of bleeding disorders or conditions which may predispose to bleeding.
Withdrawal symptoms seen on discontinuation of paroxetine treatment
Withdrawal symptoms when treatment is discontinued are common, particularly if discontinuation is abrupt (see section 4.8 Undesirable effects). In clinical trials adverse events seen on treatment discontinuation occurred in 30% of patients treated with paroxetine compared to 20% of patients treated with placebo. The occurrence of withdrawal symptoms is not the same as the drug being addictive or dependence producing.
The risk of withdrawal symptoms may be dependent on several factors including the duration and dose of therapy and the rate of dose reduction.
Dizziness, sensory disturbances (including paraesthesia and electric shock sensations), sleep disturbances (including intense dreams), agitation or anxiety, nausea, tremor, confusion, sweating, headache, diarrhoea, palpitations, emotional instability, irritability, and visual disturbances have been reported. Generally these symptoms are mild to moderate, however, in some patients they may be severe in intensity. They usually occur within the first few days of discontinuing treatment, but there have been very rare reports of such symptoms in patients who have inadvertently missed a dose.
Generally these symptoms are self-limiting and usually resolve within 2 weeks, though in some individuals they may be prolonged (2-3 months or more). It is therefore advised that paroxetine should be gradually tapered when discontinuing treatment over a period of several weeks or months, according to the patient's needs (see "Withdrawal Symptoms Seen on Discontinuation of Paroxetine", Section 4.2 Posology and Method of Administration).
4.5 Interaction With Other Medicinal Products And Other Forms Of Interaction
Serotonergic drugs
As with other SSRIs, co-administration with serotonergic drugs (including MAOIs, L-tryptophan, triptans, tramadol, linezolid, SSRIs, lithium and St. John's Wort – Hypericum perforatum – preparations) may lead to an incidence of 5-HT associated effects (serotonin syndrome: see Section 4.3 Contraindications and Section 4.4 Special Warnings and Special Precautions for Use).
Caution should be advised and a closer clinical monitoring is required when these drugs are combined with paroxetine.
Drug metabolising enzymes
The metabolism and pharmacokinetics of paroxetine may be affected by the induction or inhibition of drug metabolising enzymes.
When paroxetine is to be co-administered with a known drug metabolising enzyme inhibitor, consideration should be given to using paroxetine doses at the lower end of the range.
No initial dosage adjustment is considered necessary when the drug is to be co-administered with known drug metabolising enzyme inducers (e.g. carbamazepine, rifampicin, phenobarbital, phenytoin). Any subsequent dosage adjustment should be guided by clinical effect (tolerability and efficacy).
Procyclidine: Daily administration of paroxetine increases significantly the plasma levels of procyclidine. If anti-cholinergic effects are seen, the dose of procyclidine should be reduced.
Anticonvulsants: carbamazepine, phenytoin, sodium valproate. Concomitant administration does not seem to show any effect on pharmacokinetic/dynamic profile in epileptic patients.
CYP2D6 inhibitory potency of paroxetine
As with other antidepressants, including other SSRIs, paroxetine inhibits the hepatic cytochrome P450 enzyme CYP2D6. Inhibition of CYP2D6 may lead to increased plasma concentrations of coadministered drugs metabolised by this enzyme. These include certain tricyclic antidepressants (e.g. clomipramine, nortriptyline, and desipramine), phenothiazine neuroleptics (e.g. perphenazine and thioridazine, see section 4.3 Contraindications), risperidone, certain Type 1c antiarrhythmics (e.g. propafenone and flecainide) and metoprolol. It is not recommended to use paroxetine in combination with metoprolol when given in cardiac insufficiency, because of the narrow therapeutic index of metoprolol in this indication.
Alcohol
As with other psychotropic drugs patients should be advised to avoid alcohol use while taking paroxetine.
Oral anticoagulants
A pharmacodynamic interaction between paroxetine and oral anticoagulants may occur. Concomitant use of paroxetine and oral anticoagulants can lead to an increased anticoagulant activity and haemorrhagic risk. Therefore, paroxetine should be used with caution in patients who are treated with oral anticoagulants. (see section 4.4 Special Warnings and Special Precautions for use)
NSAIDs and acetylsalicylic acid, and other antiplatelet agents
A pharmacodynamic interaction between paroxetine and NSAIDs/acetylsalicylic acid may occur. Concomitant use of paroxetine and NSAIDs/acetylsalicylic acid can lead to an increased haemorrhagic risk. (see section 4.4 Special warnings and Special Precautions for use) Caution is advised in patients taking SSRI's, concomitantly with oral anticoagulants, drugs known to affect platelet function or increase risk of bleeding (e.g. atypical antipsychotics such as clozapine, phenothiazines, most TCA's, acetylsalicylic acid, NSAID's, COX-2 inhibitors) as well as in patients with a history of bleeding disorders or conditions which may predispose to bleeding
4.6 Pregnancy And Lactation
Pregnancy
Data on a limited number of exposed pregnancies provide no indication of an increased risk of congenital malformations in the newborn.
Paroxetine should only be used during pregnancy when strictly indicated. Women planning a pregnancy and those becoming pregnant during therapy should be asked to consult their physician. Abrupt discontinuation should be avoided during pregnancy (see "Withdrawal Symptoms Seen on Discontinuation of Paroxetine", section 4.2 Posology and Method of Administration).
Neonates should be observed if maternal use of paroxetine continues into the later stages of pregnancy, particularly the third trimester.
The following symptoms may occur in the neonate after maternal paroxetine use in later stages of pregnancy: respiratory distress, cyanosis, apnoea, seizures, temperature instability, feeding difficulty, vomiting, hypoglycaemia, hypertonia, hypotonia, hyperreflexia, tremor, jitteriness, irritability, lethargy, constant crying, somnolence and difficulty in sleeping . These symptoms could be due to either serotonergic effects or withdrawal symptoms. In a majority of instances the complications begin immediately or soon (<24 hours) after delivery.
Animal studies showed reproductive toxicity, but did not indicate direct harmful effects with respect to pregnancy, embryonal/foetal development, parturition or postnatal development (see Section 5.3 Preclinical Safety Data).
Lactation
Small amounts of paroxetine are excreted into breast milk. In published studies, serum concentrations in breast-fed infants were undetectable (<2 ng/ml) or very low (<4 ng/ml). No signs of drug effects were observed in these infants. Nevertheless, paroxetine should not be used during lactation unless the expected benefits to the mother justify the potential risks for the infant.
4.7 Effects On Ability To Drive And Use Machines
Clinical experience has shown that therapy with paroxetine is not associated with impairment of cognitive or psychomotor function. However, as with all psychoactive drugs, patients should be cautioned about their ability to drive a car and operate machinery.
Although paroxetine does not increase the mental and motor skill impairments caused by alcohol, the concomitant use of paroxetine and alcohol is not advised.
4.8 Undesirable Effects
Some of the adverse drug reactions listed below may decrease in intensity and frequency with continued treatment and do not generally lead to cessation of therapy. Adverse drug reactions are listed below by system organ class and frequency. Frequencies are defined as: very common (
Blood and lymphatic system disorders
Uncommon: abnormal bleeding, predominantly of the skin and mucous membranes (mostly ecchymosis).
Very rare: thrombocytopenia.
Immune system disorders
Very rare: allergic reactions (including urticaria and angioedema).
Endocrine disorders
Very rare: syndrome of inappropriate anti-diuretic hormone secretion (SIADH).
Metabolism and nutrition disorders
Common: decreased appetite.
Rare: hyponatraemia.
Hyponatraemia has been reported predominantly in elderly patients and is sometimes due to syndrome of inappropriate anti-diuretic hormone secretion (SIADH).
Psychiatric disorders
Common: somnolence, insomnia.
Uncommon: confusion, hallucinations.
Rare: manic reactions, agitation, anxiety, depersonalisation, panic attacks, akathisia (see section 4.4 Special Warnings and Special Precautions for use).
These symptoms may also be due to the underlying disease
Nervous system disorders
Common: dizziness, tremor
Uncommon: extrapyramidal disorders
Rare: convulsions.
Very rare: serotonin syndrome (symptoms may include agitation, confusion, diaphoresis, hallucinations, hyperreflexia, myoclonus, shivering, tachycardia and tremor).
Reports of extrapyramidal disorder including oro-facial dystonia have been received in patients sometimes with underlying movement disorders or who were using neuroleptic medication.
Eye disorders
Common: blurred vision.
Very rare: acute glaucoma.
Cardiac disorders
Uncommon: sinus tachycardia.
Rare: bradycardia.
Vascular disorders
Uncommon: transient increases or decreases in blood pressure.
Transient increases or decreases of blood pressure have been reported following treatment with paroxetine, usually in patients with pre-existing hypertension or anxiety.
Respiratory, thoracic and mediastinal disorders
Common: yawning.
Gastrointestinal disorders
Very common: nausea.
Common: constipation, diarrhoea, dry mouth.
Very rare: gastrointestinal bleeding.
Hepato-biliary disorders
Rare: elevation of hepatic enzymes.
Very rare: hepatic events (such as hepatitis, sometimes associated with jaundice and/or liver failure).
Elevation of hepatic enzymes have been reported. Post-marketing reports of hepatic events (such as hepatitis, sometimes associated with jaundice and/or liver failure) have also been received very rarely.
Discontinuation of paroxetine should be considered if there is prolonged elevation of liver function test results.
Skin and subcutaneous tissue disorders
Common: sweating.
Uncommon: skin rashes, pruritus
Very rare: photosensitivity reactions.
Renal and urinary disorders
Uncommon: urinary retention.
Reproductive system and breast disorders
Very common: sexual dysfunction.
Rare: hyperprolactinaemia/galactorrhoea.
Very rare: priapism.
Musculoskeletal disorders
Rare: arthralgia, myalgia
General disorder and administration site conditions
Common: asthenia, body weight gain
Very rare: peripheral oedema.
WITHDRAWAL SYMPTOMS SEEN ON DISCONTINUATION OF PAROXETINE TREATMENT
Common: dizziness, sensory disturbances, sleep disturbances, anxiety, headache.
Uncommon: agitation, nausea, tremor, confusion, sweating, emotional instability, visual disturbances, palpitations, diarrhoea, irritability.
Discontinuation of paroxetine (particularly when abrupt) commonly leads to withdrawal symptoms. Dizziness, sensory disturbances (including paraesthesia and electric shock sensations), sleep disturbances (including intense dreams), agitation or anxiety, nausea, tremor, confusion, sweating, headache, diarrhoea, palpitations, emotional instability, irritability, and visual disturbances have been reported.
Generally these events are mild to moderate and are self-limiting, however, in some patients they may be severe and/or prolonged. It is therefore advised that when paroxetine treatment is no longer required, gradual discontinuation by dose tapering should be carried out (see section 4.2 Posology and Method of Administration and section 4.4 Special Warnings and Special Precautions for use).
ADVERSE EVENTS FROM PAEDIATRIC CLINICAL TRIALS
In short-term (up to 10-12 weeks) clinical trials in children and adolescents, the following adverse events were observed in paroxetine treated patients at a frequency of at least 2% of patients and occurred at a rate at least twice that of placebo were: increased suicidal related behaviours (including suicide attempts and suicidal thoughts), self-harm behaviours and increased hostility. Suicidal thoughts and suicide attempts were mainly observed in clinical trials of adolescents with Major Depressive Disorder. Increased hostility occurred particularly in children with obsessive compulsive disorder, and especially in younger children less than 12 years of age. Additional events that were more often seen in the paroxetine compared to placebo group were: decreased appetite, tremor, sweating, hyperkinesia, agitation, emotional lability (including crying and mood fluctuations).
In studies that used a tapering regimen, symptoms reported during the taper phase or upon discontinuation of paroxetine at a frequency of at least 2% of patients and occurred at a rate at least twice that of placebo were: emotional lability (including crying, mood fluctuations, self-harm, suicidal thoughts and attempted suicide), nervousness, dizziness, nausea and abdominal pain (see section 4.4 Special Warnings and Special Precautions for use).
4.9 Overdose
Symptoms and Signs
A wide margin of safety is evident from available overdose information on paroxetine.
Experience of paroxetine in overdose has indicated that, in addition to those symptoms mentioned under section 4.8 "Undesirable Effects", vomiting, dilated pupils, fever, blood pressure changes, headache, involuntary muscle contractions, agitation, anxiety and tachycardia have been reported. Patients have generally recovered without serious sequelae even when doses of up to 2000 mg have been taken alone. Events such as coma or ECG changes have occasionally been reported and, very rarely with a fatal outcome, but generally when paroxetine was taken in conjunction with other psychotropic drugs, with or without alcohol.
Treatment
No specific antidote is known.
The treatment should consist of those general measures employed in the management of overdose with any antidepressant. Where appropriate, the stomach should be emptied either by the induction of emesis, lavage or both. Following evacuation, 20 to 30 g of activated charcoal may be administered every 4 to 6 h during the first 24 h after ingestion. Supportive care with frequent monitoring of vital signs and careful observation is indicated.
5. Pharmacological Properties
5.1 Pharmacodynamic Properties
Pharmacotherapeutic group: Antidepressants – selective serotonin reuptake inhibitors, ATC code: N06A B05
Mechanism of Action
Paroxetine is a potent and selective inhibitor of 5-hydroxytryptamine (5-HT, serotonin) uptake and its antidepressant action and effectiveness in the treatment of OCD, Social Anxiety disorder/Social Phobia, General Anxiety Disorder, Post-traumatic Stress Disorder and Panic Disorder is thought to be related to its specific inhibition of 5-HT uptake in brain neurones.
Paroxetine is chemically unrelated to the tricyclic, tetracyclic and other available antidepressants. Paroxetine has low affinity for muscarinic cholinergic receptors and animal studies have indicated only weak anticholinergic properties.
In accordance with this selective action, in vitro studies have indicated that, in contrast to tricyclic antidepressants, paroxetine has little affinity for alpha1, alpha2 and beta-adrenoceptors, dopamine (D2), 5-HT1 like, 5-HT2 and histamine (H1) receptors. This lack of interaction with post-synaptic receptors in vitro is substantiated by in vivo studies which demonstrate lack of CNS depressant and hypotensive properties.
Pharmacodynamic Effects
Paroxetine does not impair psychomotor function and does not potentiate the depressant effects of ethanol.
As with other selective 5-HT uptake inhibitors, paroxetine causes symptoms of excessive 5-HT receptor stimulation when administered to animals previously given monoamine oxidase (MAO) inhibitors or tryptophan.
Behavioural and EEG studies indicate that paroxetine is weakly activating at doses generally above those required to inhibit 5-HT uptake. The activating properties are not "amphetamine-like" in nature. Animal studies indicate that paroxetine is well tolerated by the cardiovascular system. Paroxetine produces no clinically significant changes in blood pressure, heart rate and ECG after administration to healthy subjects.
Studies indicate that, in contrast to antidepressants which inhibit the uptake of noradrenaline, paroxetine has a much reduced propensity to inhibit the antihypertensive effects of guanethidine.
In the treatment of depressive disorders, paroxetine exhibits comparable efficacy to standard antidepressants.
There is also some evidence that paroxetine may be of therapeutic value in patients who have failed to respond to standard therapy.
Morning dosing with paroxetine does not have any detrimental effect on either the quality or duration of sleep. Moreover, patients are likely to experience improved sleep as they respond to paroxetine therapy.
Dose response
In the fixed dose studies there is a flat dose response curve, providing no suggestion of advantage in terms of efficacy for using higher than the recommended doses. However, there are some clinical data suggesting that up-titrating the dose might be beneficial for some patients.
Long-term efficacy
The long-term efficacy of paroxetine in depression has been demonstrated in a 52 week maintenance study with relapse prevention design: 12% of patients receiving paroxetine (20-40mg daily) relapsed, versus 28% of patients on placebo.
The long-term efficacy of paroxetine in treating obsessive compulsive disorder has been examined in three 24 week maintenance studies with relapse prevention design. One of the three studies achieved a significant difference in the proportion of relapsers between paroxetine (38%) compared to placebo (59%).
The long-term efficacy of paroxetine in treating panic disorder has been demonstrated in a 24 week maintenance study with relapse prevention design: 5% of patients receiving paroxetine (10-40mg daily) relapsed, versus 30% of patients on placebo. This was supported by a 36 week maintenance study.
The long-term efficacy of paroxetine in treating social anxiety disorder and generalised anxiety disorder and Post-traumatic Stress Disorder has not been sufficiently demonstrated.
5.2 Pharmacokinetic Properties
Absorption
Paroxetine is well absorbed after oral dosing and undergoes first-pass metabolism. Due to first-pass metabolism, the amount of paroxetine available to the systemic circulation is less than that absorbed from the gastrointestinal tract. Partial saturation of the first-pass effect and reduced plasma clearance occur as the body burden increases with higher single doses or on multiple dosing. This results in disproportionate increases in plasma concentrations of paroxetine and hence pharmacokinetic parameters are not constant, resulting in non-linear kinetics. However, the non-linearity is generally small and is confined to those subjects who achieve low plasma levels at low doses.
Steady state systemic levels are attained by 7 to 14 days after starting treatment with immediate or controlled release formulations and pharmacokinetics do not appear to change during long-term therapy.
Distribution
Paroxetine is extensively distributed into tissues and pharmacokinetic calculations indicate that only 1% of the paroxetine in the body resides in the plasma.
Approximately 95% of the paroxetine present is protein bound at therapeutic concentrations.
No correlation has been found between paroxetine plasma concentrations and clinical effect (adverse experiences and efficacy).
Transfer to human breast milk, and to the foetuses of laboratory animals, occurs in small amounts.
Metabolism
The principal metabolites of paroxetine are polar and conjugated products of oxidation and methylation which are readily cleared. In view of their relative lack of pharmacological activity, it is most unlikely that they contribute to paroxetine's therapeutic effects.
Metabolism does not compromise paroxetine's selective action on neuronal 5-HT uptake.
Elimination
Urinary excretion of unchanged paroxetine is generally less than 2% of dose whilst that of metabolites is about 64% of dose. About 36% of the dose is excreted in faeces, probably via the bile, of which unchanged paroxetine represents less than 1% of the dose. Thus paroxetine is eliminated almost entirely by metabolism.
Metabolite excretion is biphasic, being initially a result of first-pass metabolism and subsequently controlled by systemic elimination of paroxetine.
The elimination half-life is variable but is generally about 1 day.
Special Patient Populations
Elderly and Renal/Hepatic Impairment
Increased plasma concentrations of paroxetine occur in elderly subjects and in those subjects with severe renal impairment or in those with hepatic impairment, but the range of plasma concentrations overlaps that of healthy adult subjects.
5.3 Preclinical Safety Data
Toxicology studies have been conducted in rhesus monkeys and albino rats; in both, the metabolic pathway is similar to that described for humans. As expected with lipophilic amines, including tricyclic antidepressants, phospholipidosis was detected in rats. Phospholipidosis was not observed in primate studies of up to one-year duration at doses that were 6 times higher than the recommended range of clinical doses.
Carcinogenesis: In two-year studies conducted in mice and rats, paroxetine had no tumorigenic effect.
Genotoxicity: Genotoxicity was not observed in a battery of in vitro and in vivo tests.
Reproduction toxicity studies in rats have shown that paroxetine affects male and female fertility. In rats, increased pup mortality and delayed ossification were observed. The latter effects were likely related to maternal toxicity and are not considered a direct effect on the foetus/neonate.
6. Pharmaceutical Particulars
6.1 List Of Excipients
Microcrystalline cellulose
croscarmellose sodium
colloidal anhydrous silica
magnesium stearate.
6.2 Incompatibilities
Not applicable.
6.3 Shelf Life
PVC/Aclar-Aluminium blister: 3 years.
PP-containers with LDPE cap: 3 years.
6.4 Special Precautions For Storage
Keep the blister in the outer carton.
6.5 Nature And Contents Of Container
PVC/Aclar-Aluminium blister:
10, 14, 20, 28, 30, 50, 56, 60, 100, 100x1 (unit dose) and 250 tablets.
PP-containers with LDPE cap: 10, 20, 50, 100 and 250 tablets.
Not all pack sizes may be marketed.
6.6 Special Precautions For Disposal And Other Handling
No special requirements.
7. Marketing Authorisation Holder
Sandoz Ltd
37 Woolmer Way
Bordon
Hampshire
GU35 9QE
8. Marketing Authorisation Number(S)
PL 04416/0583
9. Date Of First Authorisation/Renewal Of The Authorisation
20th April 2004
10. Date Of Revision Of The Text
24th October 2005
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