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PRIMIGEN is a brand name for Primidone. The medicine, its uses, side effects and dosage are the same regardless of brand.
Used for: 'Primidone' is indicated in the management of grand mal and psychomotor (temporal lobe) epilepsy. It is also of value in the management of focal or Jacksonian seizures, myoclonic jerks and akinetic attacks. Management of essential tremor.
Verbatim from this product's MHRA label. Tap a section to expand.
Posology Primidone should be started at the lowest possible dose in the evening and thereafter the dose should be increase in a stepwise manner to minimise adverse reactions. Epilepsy Treatment must always be planned on an individual basis.
In many patients primidone treatment may be given as monotherapy, but in some, Primidone will need to be combined with other anticonvulsants or with supporting therapy. In certain patients, it may be advisable to give a larger dose when the seizures are more frequent.
For instance: 1) If the attacks are nocturnal then all or most of the daily dose may be given in the evening; 2) If the attacks are associated with some particular event such as menstruation, a slight increase in the appropriate dose is often beneficial.
In adults:
Initial dose: it is usually 125 mg in a single intake in the evening. Then every 3 days, the daily dose is increased in a stepwise approach by 125 mg until the patient is receiving 500 mg daily. 5 g daily.
Maintenance dose:
Milligrams Adults 750 - 1500 Paediatric population: Initial dose: it is usually 125 mg in a single intake in the evening. Then every 3 days, the daily dose is increased in a stepwise approach by 125 mg until the patient is receiving 500 mg daily.
Thereafter, every 3 days, the daily dose (given in 2 divided doses) is increased by 250 mg in children over the age of 9 and by 125 mg in children under 9 years until control is obtained or until the maximum tolerated dose in children.
Maintenance doses:
Milligrams Children over 9 years 750 to 1500 Children 6 to 9 years 750 to 1000 Children 2 to 5 years 500 to 750 Children up to 2 years 250 to 500 Concomitant use / switch from other anticonvulsant treatments In case of lack of efficacy of other anticonvulsant treatments or in case of adverse reactions induced by these drugs, primidone may be used to increase the efficacy of the existing/underlying treatment or to replace it.
At first, primidone should be added to the previous treatment following a method of progressive dose increase as previously described. When an appreciable/acceptable therapeutic effect is reached and primidone dose has reached at least half of the previous dose, the discontinuation of the previous treatment can be attempted.
At treatment initiation, the most common side effects are drowsiness, dizziness and ataxia; they may disappear with treatment continuation and/or posology reduction. On occasions an idiosyncratic reaction may occur which involves visual disturbances, nausea, headache, dizziness, vomiting, nystagmus and ataxia; these symptoms are usually transient even when pronounced.
In an acute and severe form, withdrawal of treatment is required.
Other adverse reactions, observed during post-marketing setting, may include:
Frequencies are defined as: very rare (< 1/10,000), not known (cannot be estimated from the available data). Frequency System Organe Class Adverse reactions Common ( >1/100, <1/10) Eye disorders Visual disturbances Nervous system disorders Apathy, ataxia, nystagmus Gastrointestinal disorders Nausea Uncommon (>1/1000, <1/100) Nervous system disorders Headache, dizziness Gastrointestinal disorders Vomiting Skin and subcutaneous tissue disorders Allergic reactions particularly affecting the skin which can include maculopapular, morbilliform or scarlatiniform rashes.
Rare (>1/10000, <1/1000) Blood and lymphatic system disorders Megaloblastic anemia*, leucopenia, thrombocytopenia, lymphadenopathy Psychiatric disorders Psychotic reactions Musculoskeletal and connective tissue disorders Arthralgia, osteomalacia**.
As with phenobarbital, Dupuytren’s contracture Skin and subcutaneous tissue disorders Exfoliative dermatitis, lupus erythematosus. 4) pruritus. * Exceptionally, as with phenytoin and phenobarbital, primidone can cause megaloblastic anaemia requiring discontinuation of primidone.
This condition may respond to treatment with folic acid and/or Vitamin B12. ** Vitamin D supplementation may be needed during long-term Primidone therapy, since vitamin D catabolism may be increased. 4 Special warnings and precautions for use.
Special warnings Primidone is not efficient for the treatment of absences and myoclonic fits which may be sometimes aggravated. 2). Primidone should be given with caution and may be required in reduced dosage in children, the elderly, debilitated patients or those with impaired renal, hepatic or respiratory function.
6). Crisis aggravation Introduction of an anti-epileptic drug may be rarely followed by recrudescence of the crises or by occurrence of new type of crisis for the patient, independently of the fluctuations observed in some epilepsy.
For primidone, causes of these aggravations may be: a choice of a treatment inadequate for the crises or the epileptic syndrome in this patient, a change of the concomitant anti-epileptic treatment or a pharmacokinetic interaction, a toxicity or overdose.
There could be no other explanation than a paradoxal reaction. Treatment cessation Sudden withdrawal of a treatment at efficient anti-epileptic doses may induce convulsive fits and epilepticus status, mainly in case of alcoholism added.
Primidone is a potent CNS depressant and is partially metabolised into phenobarbital. After prolonged administration there is a potential for tolerance, dependence and a withdrawal reaction on abrupt cessation of treatment. Prevention of vitamin deficiencies Primidone is an enzymatic inducer (CYP450) which may increase the catabolism of vitamin D.
A dose-dependent increase in the risk of osteomalacia has been observed during therapy with primidone, which may predispose to the development of bone disease. 8). Exceptionally, as with phenytoin and phenobarbital, megaloblastic anaemia may develop requiring discontinuation of primidone.
8). Suicidal behaviour Suicidal ideation and behaviour have been reported in patients treated with anti- epileptic agents in several indications. A meta-analysis of randomised placebo controlled trials of anti-epileptic drugs has also shown a small increased risk of suicidal ideation and behaviour.
5)
Not medical advice. Always read the patient information leaflet and follow your prescriber or pharmacist.
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This dose adjustment is to be performed progressively for a period of 2 weeks during which it could be necessary to increase primidone doses to maintain a good control. Withdrawal of previous treatment should not be too rapid or status epilepticus may occur.
Where phenobarbital formed the major part of the previous treatment, however, both its withdrawal and Primidone substitution should be made earlier, so as to prevent excessive drowsiness from interfering with accurate assessment of the optimum dosage of Primidone.
Essential tremor Initially a dose of 50 mg daily should be introduced in a single intake late afternoon, using, when available, the 50 mg tablet. The daily dose (given in 2 divided doses) should be increased gradually over a 2 to 3-week period until remission of symptoms or the highest dose tolerated up to a maximum of 750 mg daily.
Patients not previously treated with anticonvulsants Patients with essential tremor who have not previously been exposed to anticonvulsants, or other drugs known to induce increased hepatic enzyme activity, may experience acute symptoms of intolerance to Primidone, frequently characterised by vertigo, unsteadiness and nausea.
It is, therefore, essential to respect initial dose therapeutic regimen. Special population Patients with renal impairment Due to decrease renal elimination of primidone in patients with renal insufficiency, the dose should be adjusted according to clinical response and biological monitoring.
Patients with hepatic impairment Due to the possible altered conversion of primidone to its metabolites and reduced elimination of phenobarbital in patients with severe hepatic impairment, the dose should be adjusted according to clinical response and biological monitoring.
Elderly patients It is advisable to monitor elderly patients with reduced renal function who are receiving primidone. Method of administration Oral use. The tablets should be swallowed whole with a glass of water.
**** The mechanism by which affect bone metabolism has not been identified. Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product.
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The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk for primidone. Therefore patients should be monitored for signs of suicidal ideation and behaviours and appropriate treatment should be considered.
Patients (and caregivers of patients) should be advised to seek medical advice should signs of suicidal ideation or behaviour emerge. Severe skin reactions Life-threatening cutaneous reactions Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) and drug reaction with eosinophilia and systemic symptoms (DRESS) have been reported with the use of primidone.
Patients should be advised of the signs and symptoms and monitored closely for skin reactions. The highest risk for occurrence of SJS, TEN or DRESS is within the first weeks of treatment. g. progressive skin rash often with blisters or mucosal lesions) are present, primidone treatment should be discontinued.
The best results in managing SJS, TEN and DRESS come from early diagnosis and immediate discontinuation of any suspect drug. Early withdrawal is associated with a better prognosis. If the patient has developed SJS, TEN or DRESS with the use of primidone (or phenobarbital), primidone must not be re-started in this patient at any time.
8). Women of childbearing potential Primidone is extensively metabolised to phenobarbital. Thus information on phenobarbital must be taken into account. Phenobarbital may cause foetal harm when administered to a pregnant woman. 6). Primidone should not be used in women of childbearing potential unless the potential benefit is judged to outweigh the risks following consideration of other suitable treatment options.
Women of childbearing potential should be fully informed of the potential risk to the foetus if they take primidone during pregnancy. A pregnancy test to rule out pregnancy should be considered prior to commencing treatment with primidone in women of childbearing potential.
Women of childbearing potential should use highly effective contraception during treatment and for 2 months after the last dose. Due to enzyme induction, phenobarbital may result in a failure of the therapeutic effect of oral contraceptive drugs containing oestrogen and/or progesterone.
6). Women planning a pregnancy should be advised to consult in advance with her physician so that adequate counselling can be provided and appropriate other treatment options can be discussed prior to conception and before contraception is discontinued.
Women of childbearing potential should be counselled to contact her doctor immediately if she becomes pregnant or thinks she may be pregnant while on treatment with primidone. 5). Concomitant intake of this medicinal product with alcoholic beverages or with medicinal products containing alcohol is not recommended.