- benserazide hydrochloride
POM: Prescription only medicine
This information is intended for use by health professionals
Patients not previously treated with levodopaThe recommended initial dose is one capsule or dispersible tablet of Madopar 50 mg/12.5 mg three or four times daily. If the disease is at an advanced stage, the starting dose should be one capsule or dispersible tablet of Madopar 100 mg/25 mg three times daily. The daily dosage should then be increased by one capsule or dispersible tablet of Madopar 100 mg/25 mg, or their equivalent, once or twice weekly until a full therapeutic effect is obtained, or side-effects supervene. In some elderly patients, it may suffice to initiate treatment with one capsule or dispersible tablet of Madopar 50 mg/12.5 mg once or twice daily, increasing by one capsule or dispersible tablet every third or fourth day. The effective dose usually lies within the range of four to eight capsules or dispersible tablets of Madopar 100 mg/25 mg (two to four capsules of Madopar 200 mg/50 mg) daily in divided doses, most patients requiring no more than six capsules or dispersible tablets of Madopar 100 mg/25 mg daily. Optimal improvement is usually seen in one to three weeks but the full therapeutic effect of Madopar may not be apparent for some time. It is advisable, therefore, to allow several weeks to elapse before contemplating dosage increments above the average dose range. If satisfactory improvement is still not achieved, the dose of Madopar may be increased but with caution. It is rarely necessary to give more than ten capsules or dispersible tablets of Madopar 100 mg/25 mg (five capsules of Madopar 200 mg/50 mg) per day. Treatment should be continued for at least six months before failure is concluded from the absence of a clinical response. Madopar 50 mg/12.5 mg capsules or dispersible tablets may be used to facilitate adjustment of dosage to the needs of the individual patient. Patients who experience fluctuations in response may be helped by dividing the dosage into smaller, more frequent doses with the aid of Madopar 50 mg/12.5 mg capsules or dispersible tablets without, however, altering the total daily dose. Madopar 200 mg/50 mg capsules are only for maintenance therapy once the optimal dosage has been determined using Madopar 100 mg/25 mg capsules or dispersible tablets.
Patients previously treated with levodopaThe following procedure is recommended: Levodopa alone should be discontinued and Madopar started on the following day. The patient should be initiated on a total of one less Madopar 100 mg/25 mg capsule or dispersible tablet daily than the total number of 500 mg levodopa tablets or capsules previously taken (for example, if the patient had previously taken 2g levodopa daily, then he should start on three capsules or dispersible tablets Madopar 100 mg/25 mg daily on the following day). Observe the patient for one week and then, if necessary, increase the dosage in the manner described for new patients.
Patients previously treated with other levodopa/decarboxylase inhibitor combinationsPrevious therapy should be withdrawn for 12 hours. In order to minimise the potential for any effects of levodopa withdrawal, it may be beneficial to discontinue previous therapy at night and institute Madopar therapy the following morning. The initial Madopar dose should be one capsule or dispersible tablet of Madopar 50 mg/12.5 mg three or four times daily. This dose may then be increased in the manner described for patients not previously treated with levodopa. Other anti-Parkinsonian drugs may be given with Madopar. Existing treatment with other anti-Parkinsonian drugs, e.g. anticholinergics or amantadine, should be continued during initiation of Madopar therapy. However, as treatment with Madopar proceeds and the therapeutic effect becomes apparent, the dosage of the other drugs may need to be reduced or the drugs gradually withdrawn. Elderly Although there may be an age-related decrease in tolerance to levodopa in the elderly, Madopar appears to be well-tolerated and side effects are generally not troublesome. Children Not to be given to patients under 25 years of age, therefore, no dosage recommendations are made for the administration of Madopar to children. Madopar capsules and dispersible tablets are for oral administration. They should be taken with, or immediately after, meals. Madopar dispersible tablets may be swallowed whole or dispersed in at least 25ml water per tablet. They may be taken in dilute orange squash (at least 25ml per tablet) if preferred. However, orange juice should not be used. Madopar dispersible tablets are particularly suitable for patients who dislike taking capsules or have difficulty in swallowing solid dosage forms.
Impulse control disordersPatients should be regularly monitored for the development of impulse control disorders. Patients and carers should be made aware that behavioural symptoms of impulse control disorders including pathological gambling, increased libido, hypersexuality, compulsive spending or buying, binge eating and compulsive eating can occur in patients treated with dopamine agonists and/or other dopaminergic treatments containing levodopa, including Madopar. Review of treatment is recommended if such symptoms develop.
Laboratory testsPeriodical evaluation of hepatic, haemopoietic, renal and cardiovascular function and blood count should be performed during treatment. Patients with diabetes should undergo frequent blood sugar tests and the dosage of anti-diabetic agents should be adjusted to blood sugar levels. Patients who improve on Madopar therapy should be advised to resume normal activities gradually as rapid mobilisation may increase the risk of injury.
Malignant melanomaEpidemiological studies have shown that patients with Parkinson's disease have a higher risk of developing melanoma than the general population (approximately 2-6 fold higher). It is unclear whether the increased risk observed was due to Parkinson's disease, or other factors such as levodopa used to treat Parkinson's disease. Therefore patients and providers are advised to monitor for melanomas on a regular basis when using Madopar for any indication. Ideally, periodic skin examinations should be performed by appropriately qualified individuals (e.g. dermatologists).
Pharmacokinetic interactionsCo-administration of the anticholinergic drug trihexyphenidyl with standard dosage form of Madopar reduces the rate, but not the extent, of levodopa absorption. Trihexyphenidyl given concomitantly with Madopar CR formulation does not affect the pharmacokinetics of levodopa. Ferrous sulfate decreases the maximum plasma concentration and the AUC of levodopa by 30 - 50%. The pharmacokinetic changes observed during co-treatment with ferrous sulfate appeared to be clinically significant in some but not all patients. Opioids and drugs which interfere with central amine mechanisms, such as rauwolfia alkaloids (reserpine), tetrabenazine (Nitoman), metoclopramide, phenothiazines, thioxanthenes, butyrophenones, amphetamines and papaverine, should be avoided where possible. If, however, their administration is considered essential, extreme care should be exercised and a close watch kept for any signs of potentiation, antagonism or other interactions and for unusual side-effects. Metoclopramide increases the rate of levodopa absorption. Domperidone may increase the bioavailability of levodopa by stimulation of gastric emptying.
Pharmacodynamic interactionsConcomitant administration of antipsychotics with dopamine-receptor blocking properties, particularly D2-receptor antagonists might antagonize the antiparkinsonian effects of Madopar, therefore, should be carried out with caution, and the patient carefully observed for loss of antiparkinsonian effect and worsening of parkinsonian symptoms. Symptomatic orthostatic hypotension occurred when combinations of levodopa and a decarboxylase inhibitor were added to the treatment of patients already receiving antihypertensives. Madopar needs to be introduced cautiously in patients receiving antihypertensive medication. Blood pressure needs to be monitored to allow for potential dosage adjustment of either of the drugs, if required. Concomitant administration of Madopar with sympathomimetics (agents such as epinephrine, norepinephrine, isoproterenol or amphetamine which stimulate the sympathetic nervous system) may potentiate their effects, therefore these combinations are not recommended. Should concomitant administration prove necessary, close surveillance of the cardiovascular system is essential, and the dose of the sympathomimetic agents may need to be reduced. If Madopar is to be administered to patients receiving irreversible non-selective MAO inhibitors, an interval of at least 2 weeks should be allowed between cessation of the MAO inhibitor and the start of Madopar therapy. Otherwise unwanted effects such as hypertensive crises are likely to occur (see 4.3 Contraindications). Selective MAO-B inhibitors, such as selegiline and rasagiline and selective MAO-A inhibitors, such as moclobemide, can be prescribed to patients on levodopa-benserazide. It is recommended to readjust the levodopa dose to the individual patient's needs, in terms of both efficacy and tolerability. Combination of MAO-A and MAO-B inhibitors is equivalent to non-selective MAO inhibition, and hence this combination should not be given concomitantly with Madopar (see 4.3 Contraindications). Combination with other anti-Parkinsonian agents such as anticholinergics, amantadine, selegiline, bromocriptine and dopamine agonists are permissible, though both the desired and undesired effects of treatment may be intensified. It may be necessary to reduce the dosage of Madopar or the other substance. When initiating an adjuvant treatment with a COMT inhibitor, a reduction of the dosage of Madopar may be necessary. Anticholinergics should not be withdrawn abruptly when Madopar therapy is instituted, as levodopa does not begin to take effect for some time. Levodopa may affect the results of laboratory tests for catecholamines, ketone bodies, creatinine, uric acid and glucose. The urine test results may give a false positive for ketone bodies. Levodopa therapy has been reported to inhibit the response to protirelin in tests of thyroid function. Coombs' tests may give a false-positive result in patients taking Madopar. A diminution of effect is observed when the drug is taken with a protein-rich meal. Concomitant administration of antipsychotics with dopamine-receptor blocking properties, particularly D2-receptor antagonists might antagonise the antiparkinsonian effects of levodopa-benserazide. Levodopa may reduce antipsychotic effects of these drugs. These drugs should be co-administered with caution. General anaesthesia with halothane: levodopa-benserazide should be discontinued 12-48 hours before surgical intervention requiring general anaesthesia with halothane as fluctuations in blood pressure and/or arrhythmias may occur. For general anesthesia with other anaesthetics see section 4.4.
|Blood and Lymphatic System Disorder|
|frequency not known||Haemolytic anaemia|
|Metabolic and nutritional disorders|
|frequency not known||Decreased appetite|
|frequency not known||Dopamine dysregulation syndrome|
|Eating disorder symptom|
|Nervous System Disorders|
|frequency not known||Ageusia|
|Dyskinesia (choreiform and athetotic)|
|Fluctuations in therapeutic response|
|On and off phenomenon|
|Sudden onset of sleep|
|frequency not known||Arrhythmia|
|frequency not known||Orthostatic hypotension|
|frequency not known||Nausea|
|Oral mucosa discolouration|
|Liver and Biliary disorders|
|frequency not known||Transaminases increased|
|Alkaline phosphatase increased|
|Skin and subcutaneous tissue disorders|
|frequency not known||Pruritus|
|Musculoskeletal and connective tissue disorders|
|frequency not known||Restless legs syndrome|
|Renal and urinary disorders|
|frequency not known||Blood urea increased|
Impulse Control Disorders:- Pathological gambling, increased libido, hypersexuality, compulsive spending or buying, binge eating and compulsive eating can occur in patients treated with dopamine agonists and/or other dopaminergic treatments containing levodopa including Madopar. (see section 4.4).
Nervous System Disorder:Psychiatric disturbances are common in Parkinsonian patients, including those treated with levodopa, including mild elation, anxiety, agitation, insomnia, drowsiness, depression, aggression, delusions, hallucinations, temporal disorientation and unmasking of psychoses. At later stages of the treatment, dyskinesia (e.g. choreiform or athetotic) may occur. These can usually be eliminated or be made tolerable by a reduction of dosage. With prolonged treatment, fluctuations in therapeutic response may also be encountered.They include freezing episodes, end-of-dose deterioration and the on-off effect. These can usually be eliminated or made tolerable by adjusting the dosage and by giving smaller single doses more frequently. An attempt at increasing the dosage again can subsequently be made in order to intensify the therapeutic effect. Levodopa-benserazide is associated with somnolence and has been associated very rarely with excessive daytime somnolence and sudden sleep onset episodes.
Gastrointestinal disorders:- Undesirable gastrointestinal effects, which may occur mainly in the early stages of the treatment, can largely be controlled by taking Madopar with some food or liquid or by increasing the dose slowly. - Gastro-intestinal bleeding has been reported with levodopa therapy. - Isolated cases of loss or alterations of taste.
Vascular Disorders:Orthostatic disorders commonly improve following reduction of the Madopar dosage.
Musculoskeletal and connective tissue disorders:Restless Legs Syndrome: The development of augmentation (time shift of symptoms from the evening/night into the early afternoon and evening before taking the next nightly dose, is the most common adverse effect of dopaminergic long-term treatment.
Others:- Flushing and sweating have been reported with levodopa.
Investigations:Urine may be altered in colour; usually acquiring a red-tinge, which turns dark on standing. These changes are due to metabolites and are no cause for concern. Other body fluids or tissues may also be discoloured or stained including saliva, the tongue, teeth or oral mucosa.
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.
AbsorptionLow levels of endogenous levodopa are detectable in pre-dose blood samples. After oral administration of Madopar, levodopa and benserazide are rapidly absorbed, mainly in the upper regions of the small intestine and absorption there is independent of the site. Interaction studies indicate that a higher proportion of levodopa is absorbed when administered in combination with benserazide, compared with levodopa administered alone. Maximum plasma concentrations of levodopa are reached approximately one hour after ingestion of Madopar. The absolute bioavailability of levodopa from standard Madopar is approximately 98%. The maximum plasma concentration of levodopa and the extent of absorption (AUC) increase proportionally with dose (50 200 mg levodopa). The peak levodopa plasma concentration is 30% lower and occurs later when Madopar is administered after a standard meal. Food intake generally reduces the extent of levodopa absorption by 15% but this can be variable.
DistributionLevodopa crosses the blood-brain barrier by a saturable transport system. It is not bound to plasma proteins. Benserazide does not cross the blood-brain barrier at therapeutic doses. Benserazide is concentrated mainly in the kidneys, lungs, small intestine and liver.
MetabolismThe 2 major routes of metabolism of levodopa are decarboxylation to form dopamine, which in turn is converted to a minor degree to norepinephrine and to a greater extent, to inactive metabolites, and O-methylation, forming 3-O-methyldopa, which has an elimination half-life of approximately 15 hours and accumulates in patients receiving therapeutic doses of Madopar. Decreased peripheral decarboxylation of levodopa when it is administered with benserazide is reflected in higher plasma levels of levodopa and 3-O-methyldopa. Benserazide is hydroxylated to trihydroxybenzylhydrazine in the intestinal mucosa and the liver. This metabolite is a potent inhibitor of the aromatic amino acid decarboxylase.
EliminationIn the presence of the peripheral decarboxylase inhibitor, benserazide, the elimination half-life of levodopa is approximately 1.5 hours. In elderly patients the elimination half-life is slightly (25%) longer. Clearance of levodopa is 430ml/min. Benserazide is almost entirely eliminated by metabolism. The metabolites are mainly excreted in the urine (64%) and to a small extent in faeces (24%).
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