Paracetamol
Liver damage is possible in adults who have taken 10g or more of paracetamol. Ingestion of 5g or more of paracetamol may lead to liver damage if the patient has risk factors (see below).
Risk factors
If the patient
a) Is on long term treatment with carbamazepine, phenobarbitone, phenytoin, primidone, rifampicin, St John's Wort or other drugs that induce liver enzymes.
or
b) Regularly consumes ethanol in excess of recommended amounts.
or
c) Is likely to be glutathione deplete e.g. eating disorders, cystic fibrosis, HIV infection, starvation, cachexia.
Symptoms
Symptoms of paracetamol overdose in the first 24 hours are pallor, nausea, vomiting, anorexia and abdominal pain. Liver damage may become apparent 12-48 hours after ingestion. Abnormalities of glucose metabolism and metabolic acidosis may occur. In severe poisoning, hepatic failure may progress to encephalopathy, coma and death. Acute renal failure with acute tubular necrosis strongly suggested by loin pain, haematuria and proteinuria, may develop even in the absence of severe liver damage. Cardiac arrhythmias and pancreatitis have been reported. Liver damage is possible in adults who have taken 10 g or more of paracetamol. It is considered that excess quantities of a toxic metabolite (usually adequately detoxified by glutathione when normal doses of paracetamol are ingested); become irreversibly bound to liver tissue.
Treatment
Immediate treatment is essential in the management of paracetamol overdose. Despite a lack of significant early symptoms, patients should be referred to hospital urgently for immediate medical attention. Symptoms may be limited to nausea or vomiting and may not reflect the severity of overdose or the risk of organ damage. Management should be in accordance with established treatment guidelines, see BNF overdose section.
Treatment with activated charcoal should be considered if the overdose has been taken within 1 hour. Plasma paracetamol concentration should be measured at 4 hours or later after ingestion (earlier concentrations are unreliable). Treatment with N-acetylcysteine may be used up to 24 hours after ingestion of paracetamol, however, the maximum protective effect is obtained up to 8 hours post-ingestion. The effectiveness of the antidote declines sharply after this time. If required the patient should be given intravenous N-acetylcysteine, in line with the established dosage schedule. If vomiting is not a problem, oral methionine may be a suitable alternative for remote areas, outside hospital. Management of patients who present with serious hepatic dysfunction beyond 24h from ingestion should be discussed with the NPIS or a liver unit.
Promethazine Hydrochloride
Symptoms
In children, Promethazine overdose can cause CNS stimulation and antimuscarinic effects. Promethazine overdose is likely to result in effects similar to those listed under Adverse Reactions. Additional symptoms may include delirium, agitation, hallucinations, dystonic reactions, hypotension, and ECG changes. Large overdose may cause convulsions, toxic psychosis, arrythmias, coma and cardiorespiratory depression (uncommon).
Treatment
If the patient is seen soon enough after ingestion, it should be possible to induce vomiting with ipecacuanha despite the antiemetic effect of promethazine; alternatively gastric lavage may be used. Treatment otherwise supportive with attention to maintenance of adequate respiratory and circulatory status. Convulsions and marked CNS stimulation should be treated with parenteral diazepam or other suitable anticonvulsants.
Dextromethorphan
Dextromethorphan is thought to be of low toxicity, but the effects in overdosage will be potentiated by simultaneous ingestion of alcohol and psychotropic drugs.
Symptoms
Generally, it would be dizziness, excitation, mental confusion and gastrointestinal disturbances. Following large overdoses, additional symptoms may include excitation, mental confusion ,restlessness, nervousness and irritability, stupor, ataxia, dystonia, hallucinations, psychosis and respiratory depression.
Treatment
This should include general symptomatic and supportive measures including a clear airway and monitoring of vital signs until stable. Consider activated charcoal if an adult presents within one hour of ingestion of more than 350 mg or a child more than 5 mg/kg.
Give naloxone if overdose is severe and if coma or respiratory depression is present. Naloxone is a competitive antagonist and has a short half-life, so large and repeated doses may be required in a seriously poisoned patient. Observe for at least four hours after ingestion, or eight hours if a sustained release preparation has been taken.
Hepatic or renal impairment.
With, or at risk of developing, respiratory failure (e.g. those with chronic obstructive airways disease or pneumonia, or during an asthma attack or an exacerbation of asthma).
Patients taking or have taken monoamine oxidase inhibitors (MAOIs) in the last two weeks.
Dextromethorphan, in common with other centrally acting antitussive agents, should not be given to subjects in, or at risk of developing respiratory failure.
This product is contraindicated in patients taking serotonin reuptake inhibitors.
Not to be used in children under the age of 12 years.
None known.
The following convention has been utilized for the classification of undesirable effects: very common (>1/10), common (>1/100, <1/10), uncommon (>1/1000, < 1/100), rare (>1/10,000, < 1/1000), very rare (<1/10,000), not known (cannot be estimated from available data).
Paracetamol
Adverse events of paracetamol from historical clinical trial data are both infrequent and from small patient exposure. Accordingly, events reported from extensive post-marketing experience at therapeutic/labelled dose and considered attributable are tabulated below by system class. The frequency of these adverse is not known.
| Body System | Undesirable effect |
| Blood and lymphatic system disorders | Thrombocytopenia Agranulocytosis |
| Immune system disorders | Anaphylaxis Cutaneous hypersensitivity reactions including skin rashes, angioedema and Stevens Johnson syndrome/toxic epidermal necrolysis |
| Respiratory thoracic and mediastinal disorders | Bronchospasm* |
| Hepatobiliary disorders | Hepatic dysfunction |
*There have been cases of bronchospasm with paracetamol, but these are more likely in asthmatics sensitive to aspirin or other NSAIDs.
Dextromethorphan
The following adverse events have been observed in published clinical studies and are likely to represent uncommon adverse reactions to dextromethorphan.
| Body system | Undesirable effect |
| Nervous system disorders | Drowsiness, dizziness |
| Gastrointestinal disorders | Gastrointestinal disturbance, nausea, vomiting, abdominal discomfort |
Adverse reaction identified during post-marketing use with dextromethorphan are listed below. The frequency of these reactions are not known.
| Body system | Undesirable effect |
| Immune system disorders | Allergic reactions (e.g. rash, urticaria, angiodema) |
| Nervous system disorders | Serotonin syndrome (with changes in mental status, restlessness, myoclonus, hyperreflexia, diaphoresis, shivering, tremor and hypertension) has been reported when dextromethorphan has been taken concurrently with MAOIs or serotonergic drugs such as SSRIs |
ADRs are presented by frequency category based on 1) incidence in adequately designed clinical trials or epidemiology studies, if available, or 2) when incidence cannot be estimated, frequency category is listed as 'Not known'.
| Body System | Frequency | Adverse Drug Reaction (Preferred Term) |
| Immune System Disorders | Not known Not known Not known Not known | Angioedema Pruritus Rash Urticaria |
| Psychiatric Disorders | Not known Not known | Insomnia Confusional state |
| Nervous System Disorders | Not known Not known Not known Not known | Convulsion Dizziness Psychomotor hyperactivity Somnolence |
| Respiratory, thoracic and mediastinal Disorders | Not known | Respiratory depression |
| Gastrointestinal Disorders | Not known Not known Not known Not known Not known | Abdominal pain Diarrhoea Gastrointestinal disturbance Nausea Vomiting |
Promethazine
Adverse reactions which been observed in published clinical studies with promethazine and which are considered to be common or very common are listed below by MedDRA System Organ Class. The frequency of other reactions identified during post-marketing use is not known, but these reactions are likely to be uncommon or rare.
| Body System | Undesirable effect |
| Immune system disorders | Not known: Hypersensitivity reactions including rash, urticaria, angiodema and anaphylaxis, photosensitivity |
| Psychiatric disorders | Not known: Confusion*, disorientation*, paradoxical excitation*, **(e.g. increased energy, irritability, restlessness, nervousness, sleep disturbance) |
| Nervous system disorders | Very common: Drowsiness Common: Psychomotor impairment, disturbance in attention, dizziness, headache. |
| Eye disorders | Common: Blurred vision |
| Gastrointestinal disorders | Common: Dry mouth Not Known: Gastrointestinal disturbance |
| Renal and urinary disorders | Not known: Urinary retention |
*The elderly are more susceptible to confusion, disorientation and paradoxical excitation
**Children are more susceptible to paradoxical excitation
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 the Yellow Card Scheme at www.mhra.gov.uk/yellowcard.
Preclinical safety data on these active ingredients in the literature have not revealed any pertinent and conclusive findings which are of relevance to the recommended dosage and use of the product and which have not already been mentioned elsewhere in this summary.
For the symptomatic night time relief of colds, chills and influenza consisting of headache, shivers, sore throat pain, tickly cough, runny nose, aches and pains.
| Paracetamol: other analgesics and antipyretics, anilides. | |
| Pharmacotherapeutic Group: | Analgesics and Antipyretics, Anilides |
| ATC Code: | N02B E01 |
| Promethazine Hydrochloride: an antihistamine with anticholinergic activity. | |
| Pharmacotherapeutic Group: | Antihistamines for Systemic Use, Phenothiazine derivatives |
| ATC Code: | R06A D02 |
| Dextromethorphan Hydrobromide: an antitussive | |
| Pharmacotherapeutic Group: | Cough and Cold Preparations, Opium Alkaloids and derivatives |
| ATC Code: | R05D A09 |
Paracetamol is readily absorbed from the upper gastrointestinal tract. It is metabolised predominantly in the liver and excreted in the urine, mainly as glucuronide and sulphate conjugates.
Promethazine Hydrochloride is readily absorbed from the gastrointestinal tract, but undergoes extensive first pass metabolism in the liver, with only 25% of the oral dose reaching the systemic circulation unchanged. After oral therapy, therapeutic effects are identifiable at 15-30 minutes and peak plasma concentrations at 2 to 3 hours. Estimates of terminal half life in blood plasma are in the range of 4-6 hours. It is extensively plasma protein bound. It is eliminated mainly as metabolites, predominantly by the faecal (via biliary) route, with < 1% of the patient compound and ca. 10% as the sulphoxide metabolite being excreted in the urine over a 72 hour period.
Dextromethorphan undergoes rapid and extensive first-pass metabolism in the liver after oral administration. Genetically controlled O-demethylation (CYD2D6) is the main determinant of dextromethorphan pharmacokinetics in human volunteers.
It appears that there are distinct phenotypes for this oxidation process resulting in highly variable pharmacokinetics between subjects. Unmetabolised dextromethorphan, together with the three demethylated morphinan metabolites dextrorphan (also known as 3-hydroxy-N-methylmorphinan), 3- hydroxymorphinan and 3-methoxymorphinan have been identified as conjugated products in the urine.
Dextrorphan, which also has antitussive action, is the main metabolite. In some individuals metabolism proceeds more slowly and unchanged dextromethorphan predominates in the blood and urine.
Medical advice must be sought before taking this product in people with:
- Chronic or persistent cough, such as occurs with asthma, emphysema, or other respiratory disorders; or where the cough is accompanied by excessive secretions unless directed by a physician
- Epilepsy
- Narrow- angle glaucoma
- Urinary retention
- Prostatic hypertrophy
- Cardiovascular problems
Use with caution in the elderly, who are more likely to experience anticholinergic adverse effects including confusion and paradoxical excitation. Avoid use in elderly patients with confusion.
Children are more likely to experience paradoxical excitation with sedating antihistamine.
Medical advice should be sought if symptoms persist, or are accompanied by high fever, skin rash or persistent headache.
There have been no specific studies of this product in renal or hepatic dysfunction. Due to the extensive hepatic metabolism of dextromethorphan, caution should be exercised in the presence of hepatic impairment. Underlying liver disease increases the risk of paracetamol-related liver damage.
This product should not be taken with any other cough and cold medicine.
Use of dextromethorphan with alcohol or other CNS depressants may increase the effects on the CNS and cause toxicity in relatively smaller doses.
This product should be used with caution in atopic children due to histamine release.
Patients with rare hereditary problems of fructose intolerance should not take this medicine.
The hazards of overdose are greater in those with non-cirrhotic alcoholic liver disease.
Do not exceed the stated dose. Always use the measuring cup supplied with the pack.
Patients should be advised not to take other paracetamol-containing products or decongestant-containing medicines concurrently.
If symptoms persist consult your doctor.
Keep all medicines out of sight and reach of children.
Warning: May cause drowsiness. If affected, do not drive or operate machinery.
Avoid alcoholic drink.
Cases of dextromethorphan abuse have been reported. Caution is particularly recommended for adolescents and young adults as well as in patients with a history of drug abuse or psychoactive substances.
Dextromethorphan is metabolised by hepatic cytochrome P450 2D6.).'
Special label warnings
Do not take with any other paracetamol-containing products.
Immediate medical advice should be sought in the event of an overdose, even if you feel well.
Special leaflet warnings
Immediate medical advice should be sought in the event of an overdose, even if you feel well, because of the risk of delayed, serious liver damage.
This medicinal product contains 18.08% v/v ethanol (alcohol), i.e. up to 3.5ml per 20ml dose, equivalent to 70 ml of beer, 29 ml of wine per dose.
Harmful for those suffering from alcoholism.
To be taken into account in pregnant or breast-feeding women, children and high-risk groups such as patients with liver disease, or epilepsy.
Each 20ml dose contains up to 23.52mg of sodium. This should be taken into account by patients on a controlled sodium diet.
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
Route of administration
For oral use. To be taken at bedtime. Shake the bottle before use
Maximum daily dose: Only one dose should be taken per night.
Do not exceed the stated dose
Should not be used with other cough or cold medicines, or any other antihistamine-containing products, including those used on the skin.
Adults and children aged 16 years and over:
One measured 20 ml dose to be taken just before going to bed.
Children aged 12 to 15 years:
A 10 ml to 15 ml dose to be taken just before going to bed.
Not to be given to children under 12 years.
Elderly:
The normal adult dose can be used.
Maximum duration of continued use without medical advice: 3 days.
Not applicable.
