Overdose of benzodiazepines is usually manifested by degrees of central nervous system depression ranging from drowsiness to coma. In mild cases, symptoms include drowsiness, mental confusion and lethargy, in more serious cases, symptoms may include ataxia, hypotonia, hypotension, respiratory depression, rarely coma and very rarely death. As with other benzodiazepines, overdose should not present a threat to life unless combined with other CNS depressants (including alcohol).
In the management of overdose, it is recommended that the possible involvement of multiple agents be taken into consideration.
Following overdose with oral benzodiazepines, vomiting should be induced (within one hour) if the patient is conscious, or gastric lavage undertaken with the airway protected if the patient is unconscious. If there is no advantage in emptying the stomach, activated charcoal should be given to reduce absorption. Special attention should be paid to respiratory and cardiovascular functions in intensive care.
Secondary elimination of Onfi (by forced diuresis or haemodialysis) is ineffective.
Consideration should be given to the use of flumazenil as a benzodiazepine antagonist.
Onfi 10mg Tablets must not be used:
- In patients with any history of drug or alcohol dependence (increased risk of development of dependence).
- In patients with myasthenia gravis (risk of aggravation of muscle weakness).
- In patients with severe respiratory insufficiency (risk of deterioration).
- In patients with sleep apnoea syndrome (risk of deterioration).
- In patients with severe hepatic insufficiencies (risk of precipitating encephalopathy).
- In breast-feeding women.
Benzodiazepines must not be given to children without careful assessment of the need for their use. Onfi must not be used in children between the ages of 6 months and 3 years, other than in exceptional cases for anticonvulsant treatment where there is a compelling indication. As there is no age appropriate formulation to enable safe and accurate dosing, no dosage recommendations can be made in children under 6 years of age.
None known
Nervous system disorders
Onfi may cause sedation, leading to fatigue and sleepiness, especially at the beginning of treatment and when higher doses are used. Side-effects such as slowing of reaction time, muscle weakness, ataxia, confusion, drowsiness, dizziness, numbed emotions and headaches, or a fine tremor of the fingers have been reported. These are more likely to occur at the beginning of treatment and often disappear with continued treatment or a reduction in dose.
Disorders of articulation, unsteadiness of gait and other motor functions, or loss of libido may occur, particularly with high doses or in long-term treatment. These reactions are reversible.
After prolonged use of benzodiazepines, impairment of consciousness, sometimes combined with respiratory disorders, has been reported in very rare cases, particularly in elderly patients: it sometimes persists for some length of time. These disorders have not been seen so far under Onfi treatment.
Anterograde amnesia may occur, especially at higher dose levels. Amnesia effects may be associated with inappropriate behaviour.
Psychiatric disorders
Paradoxical reactions, such as restlessness, irritability, difficulty in falling asleep or sleeping through, acute agitational states, , anxiety, aggressiveness , delusion, fits of rage, nightmare, hallucinations, psychotic reactions suicidal tendencies or frequent muscle spasms may occur, especially in elderly and in children. In the event of such reactions, treatment with Onfi must be discontinued.
Pre-existing depression may be unmasked during benzodiazepine use.
Tolerance and physical and/or psychic dependence may develop, especially during prolonged use. Discontinuation of the therapy may result in withdrawal or rebound phenomena (see Warnings and Precautions). Abuse of benzodiazepines has been reported.
When used as an adjuvant in the treatment of epilepsy, this preparation may in rare cases cause restlessness and muscle weakness.
As with other benzodiazepines, the therapeutic benefit must be balanced against the risk of habituation and dependence during prolonged use.
Eye disorders
Visual disorders (e.g., double vision, nystagmus). Such reactions occur particularly with high doses or in long-term treatment, and are reversible.
Respiratory, thoracic and mediastinal disorders
Onfi may cause respiratory depression, especially if administered in high doses. Therefore, particularly in patients with pre-existing compromised respiratory function (i.e., in patients with bronchial asthma) or brain damage, respiratory insufficiency may occur or deteriorate.
Gastrointestinal disorders
Dryness of the mouth, constipation, loss of appetite, nausea
Skin and subcutaneous tissue disorders
Cutaneous reactions, such as rash or urticaria may develop in very rare cases. Stevens-Johnson syndrome, Toxic Epidermal Necrolysis
Metabolism and nutrition disorders
Weight gain, may occur particularly with high doses or in long-term treatment. This reaction is reversible.
General disorders
Fall
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. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme, Website:www.mhra.gov.uk/yellowcard
None applicable
Onfi is a 1,5-benzodiazepine indicated for the short-term relief (2-4 weeks) only of anxiety that is severe, disabling or subjecting the individual to unacceptable distress, occurring alone or in association with insomnia or short term psychosomatic, organic or psychotic illness. The use of Onfi to treat short-term “mild†anxiety is inappropriate and unsuitable.
Before treatment of anxiety states associated with emotional instability, it must first be determined whether the patient suffers from a depressive disorder requiring adjunctive or different treatment. Indeed, in patients with anxiety associated with depression, Onfi must be used only in conjunction with adequate concomitant treatment. Use of benzodiazepine (such as Onfi) alone, can precipitate suicide in such patients.
In patients with schizophrenic or other psychotic illnesses, use of benzodiazepines is recommended only for adjunctive, i.e. not for primary treatment.
Onfi may be used as adjunctive therapy in epilepsy.
ATC Code: N05BA09 (Nervous System, Psycholeptics, Anxiolytics, Benzodiazepine derivatives, Onfi)
Onfi is a 1,5-benzodiazepine. In single doses up to 20mg or in divided doses up to 30mg, Onfi does not affect psychomotor function, skilled performance, memory or higher mental functions.
- Absorption
After oral administration, Onfi is rapidly and extensively absorbed.
Time to peak plasma concentrations (Tmax) is achieved from 0.5 - 4.0 hrs.
The administration of Onfi tablets with food or crushed in applesauce slows the rate of absorption by approximately 1 hour, but it does not affect the overall extent of absorption. Onfi can be given without regard to meals.
Concomitant intake of alcohol can increase the bioavailability of Onfi by 50%.
- Distribution
After a single dose of 20 mg Onfi, marked interindividual variability in maximum plasma concentrations (222 to 709 ng/ml) was observed after 0.25 to 4 hours. Onfi is lipophilic and distributes rapidly throughout the body. Based on a population pharmacokinetic analysis, the apparent volume of distribution at steady state was approximately 102 L, and is concentration independent over the therapeutic range. Approximately 80 - 90% of Onfi is bound to plasma protein.
Onfi accumulates approximately 23 fold to steady state while the active metabolite NdesmethylOnfi (NCLB) accumulates approximately 20 fold following Onfi twice daily administration. Steady state concentrations are reached within approximately 2 weeks.
- Metabolism
Onfi is rapidly and extensively metabolized in the liver. Onfi metabolism occurs primarily by hepatic demethylation to NdesmethylOnfi (NCLB), mediated by CYP3A4 and to a lesser extent by CYP2C19. NCLB is an active metabolite and the main circulating metabolite found in human plasma.
NCLB undergoes further biotransformation in the liver to form 4hydroxyNdesmethylOnfi, primarily mediated by CYP2C19.
CYP2C19 poor metabolizers exhibit a 5fold higher plasma concentration of NCLB compared to extensive metabolizers.
Onfi is a weak CYP2D6 inhibitor. Coadministration with dextromethorphan led to increases of 90% in AUC and 59% in Cmax values for dextromethorphan.
Concomitant administration of 400 mg ketoconazole (CYP3A4 inhibitor) increased Onfi AUC by 54% with no effect on Cmax. These changes are not considered clinically relevant.
- Elimination
Based on a population pharmacokinetic analysis, plasma elimination half lives of Onfi and NCLB were estimated to be 36 hours and 79 hours respectively.
Onfi is cleared mainly by hepatic metabolism with subsequent renal elimination. In a mass balance study, approximately 80% of the administered dose was recovered in urine and about 11% in the faeces. Less than 1 % of unchanged Onfi and less than 10% of unchanged N-CLB are excreted through the kidneys.
- Amnesia
Amnesia may occur with benzodiazepines. In case of loss or bereavement psychological adjustment may be inhibited by benzodiazepines.
Special caution is necessary if Onfi is used in patients with myasthenia gravis, spinal or cerebellar ataxia or sleep apnoea. A dose reduction may be necessary.
- Muscle weakness
Onfi can cause muscle weakness. Therefore, in patients with pre-existing muscle weakness or spinal or cerebellar ataxia or sleep apnoea, special observation is required and a dose reduction may be necessary. Onfi is contraindicated in patients with myasthenia gravis.
- Depression and personality disorders
Disinhibiting effects may be manifested in various ways. Suicide may be precipitated in patients who are depressed and aggressive behaviour towards self and others may be precipitated. Extreme caution should therefore be used in prescribing benzodiazepines in patients with personality disorders.
- Dependence
Use of benzodiazepines - including Onfi - may lead to the development of physical and psychic dependence upon these products. The risk of dependence increases with dose and duration of treatment; it is also greater in patients with a history of alcohol or drug abuse. Therefore the duration of treatment should be as short as possible (see Posology).
Once physical dependence has developed, abrupt termination of treatment will be accompanied by withdrawal symptoms (or rebound phenomena). Rebound phenomena are characterised by a recurrence in enhanced form of the symptoms which originally led to Onfi treatment. This may be accompanied by other reactions including mood changes, anxiety or sleep disturbances and restlessness.
A withdrawal syndrome may also occur when abruptly changing over from a benzodiazepine with a long duration of action (for example, Onfi) to one with a short duration of action.
- Serious Skin Reaction
Serious skin reactions, including Stevens Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), have been reported with Onfi in both children and adults during the postmarketing experience. A majority of the reported cases involved the concomitant use of other drugs, including antiepileptic drugs that are associated with serious skin reactions. SJS/TEN could be associated with a fatal outcome. Patients should be closely monitored for signs or symptoms of SJS/TEN, especially during the first 8 weeks of treatment. Onfi should be immediately discontinued when SJS/TEN is suspected. If signs or symptoms suggest SJS/TEN, use of this drug should not be resumed and alternative therapy should be considered.
- Respiratory Depression
Respiratory function should be monitored in patients with chronic or acute severe respiratory insufficiency and a dose reduction of Onfi may be necessary.).
- Renal and hepatic impairment
In patients with impairment of renal or hepatic function, responsiveness to Onfi and susceptibility to adverse effects are increased, and a dose reduction may be necessary. In long-term treatment renal and hepatic function must be checked regularly.
- Elderly patients
In the elderly, due to the increased sensitivity to adverse reactions such as drowsiness, dizziness, muscle weakness, there is an increased risk of fall that may result in serious injury. A dose reduction is recommended.
- Tolerance in epilepsy
In the treatment of epilepsy with benzodiazepines - including Onfi - consideration must be given to the possibility of a decrease in anticonvulsant efficacy (development of tolerance) in the course of treatment.
- CYP2C19 poor metabolisers
In patients who are CYP2C19 poor metabolisers, levels of the active metabolite N-desmethylOnfi are expected to be increased as compared to extensive metabolisers.)).
- Alcohol
Onfi 10mg Tablets contain lactose; patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Sedation, amnesia, impaired concentration and impaired muscular function may adversely affect the ability to drive or to use machines. If insufficient sleep duration occurs, the likelihood of impaired alertness may be increased (see also Interactions).
This medicine can impair cognitive function and can affect a patient's ability to drive safely. This class of medicine is in the list of drugs included in regulations under 5a of the Road Traffic Act 1988. When prescribing this medicine, patients should be told:
- The medicine is likely to affect your ability to drive
- Do not drive until you know how the medicine affects you
- It is an offence to drive while under the influence of this medicine
- However, you would not be committing an offence (called 'statutory defence') if:
o The medicine has been prescribed to treat a medical or dental problem and
o You have taken it according to the instructions given by the prescriber and in the information provided with the medicine and
o It was not affecting your ability to drive safely
Treatment of anxiety
The usual anxiolytic dose for adults is 20-30mg daily in divided doses or as a single dose given at night. Doses up to 60mg daily have been used in the treatment of adult in-patients with severe anxiety.
The lowest dose that can control symptoms should be used. After improvement of the symptoms, the dose may be reduced.
It should not be used for longer than 4 weeks. Long term chronic use as an anxiolytic is not recommended. In certain cases, extension beyond the maximum treatment period may be necessary; treatment must not be extended without re-evaluation of the patient's status using special expertise. It is strongly recommended that prolonged periods of uninterrupted treatment be avoided, since they may lead to dependence. Treatment should always be withdrawn gradually. Patients who have taken Onfi for a long time may require a longer period during which doses are reduced.
Anxiolytic treatment should be limited to the lowest possible dose for the shortest possible time (see CSM advice). Dependence is particularly likely in patients with a history of alcohol or drug abuse and in patients with marked personality disorders.
CSM advice:
1. Benzodiazepines are indicated for the short-term relief (two to four weeks only) of anxiety that is severe, disabling or subjecting the individual to unacceptable distress, occurring alone or in association with insomnia or short-term psychosomatic, organic or psychotic illness.
2. Benzodiazepines should be used to treat insomnia only when it is severe, disabling, or subjecting the individual to extreme distress.
Withdrawal of a benzodiazepine should be gradual because abrupt withdrawal may produce confusion, toxic psychosis, convulsions, or a condition resembling delirium tremens. The benzodiazepine withdrawal syndrome may develop at any time up to 3 weeks after stopping a long-acting benzodiazepine, but may occur within a few hours in the case of a short-acting one. It is characterised by insomnia, anxiety, loss of appetite and of body-weight, tremor, perspiration, tinnitus, and perceptual disturbances. These symptoms may be similar to the original complaint and encourage further prescribing; some symptoms may continue for weeks or months after stopping benzodiazepines.
A benzodiazepine can be withdrawn in steps of about one-eighth (range one-tenth to one-quarter) of the daily dose every fortnight. A suggested withdrawal protocol for patients who have difficulty is as follows:
1. Transfer patient to equivalent daily dose of diazepam preferably taken at night
2. Reduce diazepam dose in fortnightly steps of 2 or 2.5mg; if withdrawal symptoms occur, maintain this dose until symptoms improve
3. Reduce dose further, if necessary in smaller fortnightly steps; it is better to reduce too slowly rather than too quickly
4. Stop completely; time needed for withdrawal can vary from about 4 weeks to a year or more
Counselling may help; beta-blockers should only be tried if other measures fail; antidepressants should be used only for clinical depression or for panic disorder; avoid antipsychotics (which may aggravate withdrawal symptoms).
Elderly: Doses of 10-20mg daily in anxiety may be used in the elderly, who are more sensitive to the effects of psychoactive agents. Treatment requires low initial doses and gradual dose increments under careful observation.
Treatment of epilepsy in association with one or more other anticonvulsants
By mouth
Adults: In epilepsy a starting dose of 20-30mg daily is recommended, increasing as necessary up to a maximum of 60mg daily.
Adjunctive therapy for epilepsy
Monotherapy under specialist supervision for catamenial (menstruation) seizures (usually for 7-10 days just before and during menstruation)
Cluster seizures
Paediatric patients aged 6 years and above:
When prescribed for children treatment requires low initial doses and gradual dose increments under careful observation. It is recommended that normally treatment should be started at 5mg daily. A maintenance dose of 0.3 to 1mg/kg body weight daily is usually sufficient.
As there is no age appropriate formulation to enable safe and accurate dosing, no dosage recommendations can be made in children under 6 years of age.
Tablets should be swallowed without chewing with sufficient amount of liquid (1/2 glass)
The patient must be re-assessed after a period not exceeding 4 weeks and regularly thereafter in order to evaluate the need for continued treatment. A break in therapy may be beneficial if drug exhaustion develops, recommencing therapy at a low dose. At the end of treatment (including in poor-responding patients), since the risk of withdrawal phenomena/rebound phenomena is greater after abrupt discontinuation of treatment, it is recommended to gradually decrease the dosage.
No special requirements.
