POM: Prescription only medicine
This information is intended for use by health professionals
AdultsThe effective daily dose is usually between 15 and 45mg; the starting dose is 15 or 30mg.Mirtazapine begins to exert its effect in general after 1-2 weeks of treatment. Treatment with an adequate dose should result in a positive response within 2-4 weeks. With an insufficient response, the dose can be increased up to the maximum dose. If there is no response within a further 2-4 weeks, then treatment should be stopped.
ElderlyThe recommended dose is the same as that for adults. In elderly patients an increase in dosing should be done under close supervision to elicit a satisfactory and safe response.
Paediatric populationMirtazapine should not be used in children and adolescents under the age of 18 years (see section 4.4) as efficacy was not demonstrated in two short-term clinical trials (see section 5.1) and because of safety concerns (see sections 4.4, 4.8 and 5.1).
Renal impairmentThe clearance of mirtazapine may be decreased in patients with moderate to severe renal impairment (creatinine clearance <40ml/min). This should be taken into account when prescribing Mirtazapine to this category of patients (see section 4.4).
Hepatic impairmentThe clearance of mirtazapine may be decreased in patients with hepatic impairment. This should be taken into account when prescribing Mirtazapine to this category of patients, particularly with severe hepatic impairment, as patients with severe hepatic impairment have not been investigated (see section 4.4).Mirtazapine has an elimination half-life of 20-40 hours and therefore Mirtazapine is suitable for once daily administration. It should be taken preferably as a single night-time dose before going to bed. Mirtazapine may also be given in two divided doses (once in the morning and once at night-time, the higher dose should be taken at night).Patients with depression should be treated for a sufficient period of at least 6 months to ensure that they are free from symptoms.It is recommended to discontinue treatment with mirtazapine gradually to avoid withdrawal symptoms (see section 4.4).
Method of administrationThe tablets should be taken orally, with fluid, and swallowed without chewing.
Paediatric populationMirtazapine should not be used in the treatment of children and adolescents under the age of 18 years. Suicide-related behaviours (suicide attempt and suicidal thoughts), and hostility (predominantly aggression, oppositional behaviour and anger) were more frequently observed in clinical trials among children and adolescents treated with antidepressants compared to those treated with placebo. If, based on clinical need, a decision to treat is nevertheless taken, the patient should be carefully monitored for the appearance of suicidal symptoms. In addition, long-term safety data in children and adolescents concerning growth, maturation and cognitive and behavioural development are lacking.
Suicide/suicidal thoughts or clinical worseningDepression is associated with an increased risk of suicidal thoughts, self harm and suicide (suicide related events). 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 that the risk of suicide may increase in the early stages of recovery.Patients with a history of suicide-related events or those exhibiting a significant degree of suicidal ideation prior to commencement of treatment are known to be at greater risk of suicidal thoughts or suicide attempts, and should receive careful monitoring during treatment. A meta-analysis of placebo controlled clinical trials of antidepressants in adult patients with psychiatric disorders showed an increased risk of suicidal behaviour with antidepressants compared to placebo in patients less than 25 years old.Close supervision of patients and in particular those at high risk should accompany therapy with antidepressants especially in early treatment and following dose changes. Patients (and care givers of patients) should be alerted about the need to monitor for any clinical worsening, suicidal behaviour or thoughts and unusual changes in behaviour and to seek medical advice immediately if these symptoms present.With regard to the chance of suicide, in particular at the beginning of treatment, only a limited number of Mirtazapine film-coated tablets should be given to the patient.
Bone marrow depressionBone marrow depression, usually presenting as granulocytopenia or agranulocytosis, has been reported during treatment with mirtazapine. Reversible agranulocytosis has been reported as a rare occurrence in clinical studies with mirtazapine. In the postmarketing period with mirtazapine very rare cases of agranulocytosis have been reported, mostly reversible, but in some cases fatal. Fatal cases mostly concerned patients with an age above 65. The physician should be alert for symptoms like fever, sore throat, stomatitis or other signs of infection; when such symptoms occur, treatment should be stopped and blood counts taken.
JaundiceTreatment should be discontinued if jaundice occurs.
Conditions which need supervisionCareful dosing as well as regular and close monitoring is necessary in patients with: epilepsy and organic brain syndrome: Although clinical experience indicates that epileptic seizures are rare during mirtazapine treatment, as with other antidepressants, Mirtazapine should be introduced cautiously in patients who have a history of seizures. Treatment should be discontinued in any patient who develops seizures, or where there is an increase in seizure frequency. hepatic impairment: Following a single 15mg oral dose of mirtazapine, the clearance of mirtazapine was approximately 35% decreased in mild to moderate hepatically impaired patients, compared to subjects with normal hepatic function. The average plasma concentration of mirtazapine was about 55% increased. renal impairment: Following a single 15mg oral dose of mirtazapine, in patients with moderate (creatinine clearance <40ml/min) and severe (creatinine clearance <10ml/min) renal impairment the clearance of mirtazapine was about 30% and 50% decreased respectively, compared to normal subjects. The average plasma concentration of mirtazapine was about 55% and 115% increased respectively. No significant differences were found in patients with mild renal impairment (creatinine clearance <80ml/min) as compared to the control group. cardiac diseases like conduction disturbances, angina pectoris and recent myocardial infarction, where normal precautions should be taken and concomitant medicines carefully administered low blood pressure diabetes mellitus: In patients with diabetes, antidepressants may alter glycaemic control. Insulin and/or oral hypoglycaemic dosage may need to be adjusted and close monitoring is recommended.Like with other antidepressants, the following should be taken into account: Worsening of psychotic symptoms can occur when antidepressants are administered to patients with schizophrenia or other psychotic disturbances; paranoid thoughts can be intensified When the depressive phase of bipolar disorder is being treated, it can transform into the manic phase. Patients with a history of mania/hypomania should be closely monitored. Mirtazapine should be discontinued in any patient entering a manic phase. Although mirtazapine is not addictive, post-marketing experience shows that abrupt termination of treatment after long term administration may sometimes result in withdrawal symptoms. The majority of withdrawal reactions are mild and self-limiting. Among the various reported withdrawal symptoms, dizziness, agitation, anxiety, headache and nausea are the most frequently reported. Even though they have been reported as withdrawal symptoms, it should be realized that these symptoms may be related to the underlying disease. As advised in section 4.2, it is recommended to discontinue treatment with mirtazapine gradually. Care should be taken in patients with micturition disturbances like prostate hypertrophy and in patients with acute narrow-angle glaucoma and increased intra-ocular pressure (although there is little chance of problems with Mirtazapine because of its very weak anticholinergic activity). Akathisia/psychomotor restlessness: The use of antidepressants have been associated with the development of akathisia, characterised by a subjectively unpleasant or distressing restlessness and need to move often accompanied by an inability to sit or stand still. 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.
HyponatraemiaHyponatraemia, probably due to inappropriate antidiuretic hormone secretion (SIADH), has been reported very rarely with the use of mirtazapine. Caution should be exercised in patients at risk, such as elderly patients or patients concomitantly treated with medications known to cause hyponatraemia.
Serotonin syndromeInteraction with serotonergic active substances: serotonin syndrome may occur when selective serotonin reuptake inhibitors (SSRIs) are used concomitantly with other serotonergic active substances (see section 4.5). Symptoms of serotonin syndrome may be hyperthermia, rigidity, myoclonus, autonomic instability with possible rapid fluctuations of vital signs, mental status changes that include confusion, irritability and extreme agitation progressing to delirium and coma. Caution should be advised and a closer clinical monitoring is required when these active substances are combined with mirtazapine. Treatment with mirtazapine should be discontinued if such events occur and supportive symptomatic treatment initiated. From post marketing experience it appears that serotonin syndrome occurs very rarely in patients treated with mirtazapine alone (see section 4.8).
Elderly patientsElderly patients are often more sensitive, especially with regard to the undesirable effects of antidepressants. During clinical research with mirtazapine, undesirable effects have not been reported more often in elderly patients than in other age groups.
LactoseThis medicinal product contains lactose. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Pharmacodynamic interactions- Mirtazapine should not be administered concomitantly with MAO inhibitors or within two weeks after discontinuation of MAO inhibitor therapy. In the opposite way about two weeks should pass before patients treated with mirtazapine should be treated with MAO inhibitors (see section 4.3).In addition, as with SSRIs, co-administration with other serotonergic active substances (L-tryptophan, triptans, tramadol, linezolid, SSRIs, venlafaxine, lithium and St. John's Wort Hypericum perforatum preparations) may lead to an incidence of serotonin associated effects (serotonin syndrome: see section 4.4). Caution should be advised and a closer clinical monitoring is required when these active substances are combined with mirtazapine.- Mirtazapine may increase the sedating properties of benzodiazepines and other sedatives (notably most antipsychotics, antihistamine H1 antagonists, opioids). Caution should be exercised when these medicinal products are prescribed together with mirtazapine.- Mirtazapine may increase the CNS depressant effect of alcohol. Patients should therefore be advised to avoid alcoholic beverages while taking mirtazapine.- Mirtazapine dosed at 30mg once daily caused a small but statistically significant increase in the international normalized ratio (INR) in subjects treated with warfarin. As at a higher dose of mirtazapine a more pronounced effect can not be excluded, it is advisable to monitor the INR in case of concomitant treatment of warfarin with mirtazapine.
Pharmacokinetic interactions- Carbamazepine and phenytoin, CYP3A4 inducers, increased mirtazapine clearance about twofold, resulting in a decrease in average plasma mirtazapine concentration of 60% and 45%, respectively. When carbamazepine or any other inducer of hepatic metabolism (such as rifampicin) is added to mirtazapine therapy, the mirtazapine dose may have to be increased. If treatment with such medicinal product is discontinued, it may be necessary to reduce the mirtazapine dose.- Co-administration of the potent CYP3A4 inhibitor ketoconazole increased the peak plasma levels and the AUC of mirtazapine by approximately 40% and 50% respectively.- When cimetidine (weak inhibitor of CYP1A2, CYP2D6 and CYP3A4) is administered with mirtazapine, the mean plasma concentration of mirtazapine may increase more than 50%. Caution should be exercised and the dose may have to be decreased when co-administering mirtazapine with potent CYP3A4 inhibitors, HIV protease inhibitors, azole antifungals, erythromycin, cimetidine or nefazodone.- Interaction studies did not indicate any relevant pharmacokinetic effects on concurrent treatment of mirtazapine with paroxetine, amitriptyline, risperidone or lithium.
PregnancyLimited data of the use of mirtazapine in pregnant women do not indicate an increased risk for congenital malformations. Studies in animals have not shown any teratogenic effects of clinical relevance, however developmental toxicity has been observed (see section 5.3). Caution should be exercised when prescribing to pregnant women. If Mirtazapine is used until, or shortly before birth, postnatal monitoring of the newborn is recommended to account for possible discontinuation effects. Epidemiological data have suggested that the use of SSRIs in pregnancy, particularly in late pregnancy, may increase the risk of persistent pulmonary hypertension in the newborn (PPHN). Although no studies have investigated the association of PPHN to mirtazapine treatment, this potential risk cannot be ruled out taking into account the related mechanism of action (increase in serotonin concentrations).BreastfeedingAnimal studies and limited human data have shown excretion of mirtazapine in breast milk only in very small amounts. A decision on whether to continue/discontinue breast-feeding or to continue/discontinue therapy with Mirtazapine should be made taking into account the benefit of breastfeeding to the child and the benefit of Mirtazapine therapy to the woman.
Table 1. Adverse reactions of mirtazapine
|System organ class||Very common (≥1/10)||Common (≥1/100 to <1/10)||Uncommon (≥1/1,000 to <1/100)||Rare (≥1/10,000 to <1/1,000)||Frequency not known|
|Blood and the lymphatic system disorders||Bone marrow depression (granulocytopenia, agranulocytosis, aplastic anemia thrombocytopenia) Eosinophilia|
|Endocrine disorders||Inappropriate antidiuretic hormone secretion|
|Metabolism and nutrition disorders||Increase in appetite1 Weight increased1||Hyponatraemia|
|Psychiatric disorders||Abnormal dreams Confusion Anxiety2, 5 Insomnia3, 5||Nightmares2 Mania Agitation2 Hallucinations Psychomotor restlessness (incl. akathisia, hyperkinesia)||Aggression||Suicidal ideation6 Suicidal behaviour6|
|Nervous system disorders||Somnolence1, 4 Sedation1, 4 Headache2||Lethargy1 Dizziness Tremor||Paraesthesia2 Restless legs Syncope||Myoclonus||Convulsions (insults) Serotonin syndrome Oral paraesthesia Dysarthria|
|Vascular disorders||Orthostatic hypotension||Hypotension2|
|Gastrointestinal disorders||Dry mouth||Nausea3 Diarrhea2 Vomiting2 Constipation1||Oral hypoaesthesia||Pancreatitis||Mouth oedema Increased salivation|
|Hepatobiliary disorders||Elevations in serum transaminase activities|
|Skin and subcutaneous tissue disorders||Exanthema2||Stevens-Johnson Syndrome Dermatitis bullous Erythema multiforme Toxic epidermal necrolysis|
|Musculoskeletal and connective tissue disorders||Arthralgia Myalgia Back pain1||Rhabdomyolysis|
|Renal and urinary disorders||Urinary retention|
|General disorders and administration site conditions||Oedema peripheral1 Fatigue||Somnambulism|
|Investigations||Increased creatinine kinase|
Paediatric populationThe following adverse events were observed commonly in clinical trials in children: weight gain, urticaria and hypertriglyceridaemia (see also section 5.1).
Reporting of suspected adverse reactionsReporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme; website: www.mhra.gov.uk/yellowcard
Mechanism of actionMirtazapine is a centrally active presynaptic α2-antagonist, which increases central noradrenergic and serotonergic neurotransmission. The enhancement of serotonergic neurotransmission is specifically mediated via 5-HT1 receptors, because 5-HT2 and 5-HT3 receptors are blocked by mirtazapine. Both enantiomers of mirtazapine are presumed to contribute to the antidepressant activity, the S(+) enantiomer by blocking α2 and 5-HT2 receptors and the R(-) enantiomer by blocking 5-HT3 receptors.The histamine H1-antagonistic activity of mirtazapine is associated with its sedative properties. It has practically no anticholinergic activity and, at therapeutic doses, has practically no effect on the cardiovascular system.
Paediatric populationTwo randomised, double-blind, placebo-controlled trials in children aged between 7 and 18 years with major depressive disorder (n=259) using a flexible dose for the first 4 weeks (15-45mg mirtazapine) followed by a fixed dose (15, 30 or 45 mg mirtazapine) for another 4 weeks failed to demonstrate significant differences between mirtazapine and placebo on the primary and all secondary endpoints. Significant weight gain (≥7%) was observed in 48.8% of the mirtazapine treated subjects compared to 5.7% in the placebo arm. Urticaria (11.8% vs 6.8%) and hypertriglyceridaemia (2.9% vs 0%) were also commonly observed.
AbsorptionAfter oral administration of mirtazapine, the active substance mirtazapine is rapidly and well absorbed (bioavailability ≈ 50%), reaching peak plasma levels after approx. two hours.
DistributionBinding of mirtazapine to plasma proteins is approx. 85%.
EliminationThe mean half-life of elimination is 20-40 hours; longer half-lives, up to 65 hours, have occasionally been recorded and shorter half-lives have been seen in young men. The half-life of elimination is sufficient to justify once-a-day dosing. Steady state is reached after 3-4 days, after which there is no further accumulation.
Linearity/non-linearityMirtazapine displays linear pharmacokinetics within the recommended dose range. Food intake has no influence on the pharmacokinetics of mirtazapine.
BiotransformationMirtazapine is extensively metabolized and eliminated via the urine and faeces within a few days. Major pathways of biotransformation are demethylation and oxidation, followed by conjugation. In vitro data from human liver microsomes indicate that cytochrome P450 enzymes CYP2D6 and CYP1A2 are involved in the formation of the 8-hydroxy metabolite of mirtazapine, whereas CYP3A4 is considered to be responsible for the formation of the N-demethyl and N-oxide metabolites. The demethyl metabolite is pharmacologically active and appears to have the same pharmacokinetic profile as the parent compound.The clearance of mirtazapine may be decreased as a result of renal or hepatic impairment.
Coating:HypromelloseMacrogol 8000Titanium dioxide (E171). Talc
Pack sizes10, 14, 20, 28, 30, 50, 56 and 100 tablets in clear PVC/Al blister.30, 100 and 500 tablets in white HDPE (Duma) tablet containers with LDPE caps.The pack size of 500 tablets is intended for hospital use. Not all pack sizes may be marketed.