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Lower respiratory tract infections


12 Oct 2011

It is important to differentiate between acute bronchitis and pneumonia, as the latter is a more severe infection with a higher risk of complications. Acute bronchitis is used to describe an acute RTI, which has the predominant symptom of cough, with or without sputum production that lasts up to three weeks. A diagnosis is usually made if there is no clinical or x-ray evidence of pneumonia, and a diagnosis of a common cold, pneumonia and asthma has been excluded.

This contrasts with community acquired pneumonia, which is defined as symptoms of an acute lower respiratory tract illness (cough and at least one other lower respiratory tract symptom), new focal chest signs on examination, and at least one systemic feature (eg sweating, fevers, shivers, aches and pains and/or temperature of 38°C or more). Chest x-rays are usually only required in patients with signs and symptoms suggestive of severe pneumonia, and so are not required in outpatient settings. However, if a chest x-ray is performed, new radiographic shadowing (usually described as consolidation) is observed in patients with pneumonia, but is clear in acute bronchitis.

Acute bronchitis
The main causes of acute bronchitis are respiratory viral infections, such as influenza B, influenza A, parainfluenza and respiratory syncytial virus (RSV). Influenza outbreaks result in significant morbidity and rapidly spread in the general population, causing symptoms such as myalgia, weakness, cough, fever and nasal congestion. Bacterial infection causes less than 10 per cent of acute bronchitis, but common pathogens include Mycoplasma pneumoniae, Chlamydophila pneumoniae, Bordetella pertussis, and Bordetella parapertussis.

Antibiotics are rarely required to treat acute bronchitis, although a systematic review found a small benefit of antibiotic therapy compared to placebo. After antibiotic treatment, patients were less likely to have a cough and an abnormal lung examination, and were also less likely to show no improvement on the clinician’s global assessment. However, antibiotic treatment only reduced the number of days feeling ill by an average of 0.64 days and the duration of cough by 0.58 days, and was associated with an increase in adverse effects. Consequently, while there may be a small clinical improvement with antibiotics, there is only a small reduction in the duration of symptoms. Therefore, any benefit of treatment should be weighed against the risks, such as potential side effects (eg diarrhoea, vomiting and rash), increased antimicrobial resistance and cost.

An alternative strategy is to provide a delayed antibiotic prescribing strategy, such that on initial presentation the patient is provided with verbal and written information that no antibiotics are usually required for acute bronchitis, but if symptoms do not improve within a week or two, then a prescription can be provided. This strategy has been shown to be equally effective on symptom severity, and duration of illness as immediate prescribing strategies and has the advantage of reducing unnecessary antibiotic use and improving patients’ beliefs about antibiotics.

There are certain scenarios where immediate antibiotic treatment may be justified, particularly if the patient:

  • Is systemically very unwell;
  • Has pre-existing co-morbidities that place them at high risk of serious complications (eg significant heart, lung, renal, liver or neuromuscular disease, immunosuppression, cystic fibrosis, and young children who were born prematurely)
  • Is aged over 65 years with acute cough and at least two of the following criteria, or aged over 80 years with acute cough and at least one of the following criteria: hospitalisation within the previous year, diabetes, congestive heart failure or current use of oral corticosteroids.

When indicated, the appropriate antibiotics for the treatment of acute bronchitis are a five day course of either amoxicillin 500mg three times daily, or doxycycline 200mg loading dose, followed by 100mg daily.

Community acquired pneumonia
The annual incidence of CAP is between 5-11 per thousand adult population and accounts for between 5-12 per cent of all GP consultations for LRTIs. Mortality of community managed CAP is very low (less than one per cent), but varies from 5.7-14 per cent in hospitalised patients. The main bacterial causes of community acquired pneumonia (CAP) in the UK are Streptococcus pneumoniae and Haemophilus influenzae.

As CAP can present as either a mild and self-limiting illness, or as a serious life-threatening disease, it is important that the severity of the disease is determined. In clinical practice a severity assessment is made using a model known as the CURB-65 score. This is a six point scoring system where the patient scores one point for each of Confusion, Urea >7 mmol/l, Respiratory rate >30/min, low systolic (<90 mm Hg) or diastolic (≤60 mm Hg) Blood pressure, age ≥65 years. This allows patients to be stratified according to increasing risk of mortality. In community settings, an abbreviated CURB-65 score is used when only clinical parameters are considered. Since patients with a score of zero are at low risk of death, they can be safely treated in the community, whilst those with a score of one or two should be considered for hospital referral for assessment. Patients with a score of three or more are at a high risk of death and require urgent hospital admission for treatment.

Antibiotic treatment is required for all patients diagnosed with CAP, and the choice and duration depends on the severity of their initial illness (see Antibiotic treatment options).

Antibiotic prescribing
The appropriate choice of antibiotic should be based on a knowledge of antibiotic guidelines for treating respiratory tract infections, such as those written by the British Thoracic Society, and the British Infection Society and Health Protection Agency, as well as taking into account local antibiotic resistance patterns. When patients are given prescriptions for common antibiotics such as amoxicillin, clarithromycin and doxycycline, it is important that the pharmacist considers each patient’s allergy status, and potential for drug interactions. Clarithromycin and other macrolide antibiotics inhibit cytochrome P450 enzymes and may interact with a number of commonly used drugs such as antiepileptics, warfarin, theophylline, and statins. Doxycycline also interacts with a number of drugs, and its absorption is reduced when taken at the same time as calcium, magnesium, zinc and iron containing preparations.

Symptomatic treatment
Patients presenting with LTRIs may requesting over the counter treatment for a variety of symptoms, including cough, fever, sputum production and chest pain. Patients should be advised to rest and drink plenty of fluids, especially when febrile. Paracetamol or aspirin are effective as an antipyretic and analgesic.

Acute cough is a common symptom and is a useful defence mechanism for clearing sputum, so cough suppression is not appropriate. However, in the presence of a non-productive cough, the use of cough suppressants such at dextromethorphan or codeine linctus may be justified, although there is a lack of evidence for their benefit. There is also a lack of evidence to demonstrate a beneficial effect for treatment with expectorant or mucolytic agents in patients with productive coughs, despite their widespread use in the general population.

Recognising warning signs
While it may be appropriate for the pharmacist to advise on the management of simple symptoms such as cough, it is important that they are aware of warning symptoms that may be suggestive of more serious illness, and consequently when to refer to the GP (see panel). Such conditions may include exacerbations of asthma, pneumonia, pulmonary embolism, adverse drug reactions, or lung cancer. For example, patients reporting symptoms of cough persisting for more than three weeks should be referred to their GP, particularly if there are other associated symptoms such as haemoptysis, weight loss and breathlessness, as these symptoms may be suggestive of lung cancer and urgent chest x-ray may be required.

Antibiotic treatment options for community acquired pneumonia

Low severity (CRB-65 = 0)

  • Preferred treatment; Amoxicillin 500mg three times daily (seven days)
  • Alternative treatment;Doxycycline 200 mg loading dose, then 100 mg daily (seven days) or Clarithromycin 500 mg twice daily (seven days)

Moderate Severity (CRB-65 = 1-2) Consider hospital referral

  • Preferred treatment; Amoxicillin 500mg three times daily and Clarithromycin 500 mg twice daily (7-10 days)
  • Alternative treatment; Doxycycline 200 mg loading dose then 100 mg daily (7-10 days) or Levofloxacin 500mg daily (7-10 days)

High Severity (CRB-65 = 3+)

  • Treatment; Intravenous Co-amoxiclav 1.2g three times daily and Clarithromycin 500 mg twice daily (7-10 days)

Warning symptoms that should prompt referral to a doctor

  • Significant heart, lung, renal, liver or neuromuscular disease, immunosuppression, cystic fibrosis and young children who were born prematurely
  • Dyspnoea, difficulty in breathing, or wheezing
  • No improvement in condition after two to three weeks n Persistent cough for longer than three weeks
  • Recurrent cough
  • Dry night time cough in children
  • Haemoptysis
  • Chest pain
  • Weight loss
  • General malaise, feeling systemically unwell, persisting sweats or fever
  • Painful or swollen, inflamed calf
  • Potential for adverse drug reaction (eg ACE inhibitor)

Dr Toby Capstick
is lead respiratory pharmacist at
Leeds Teaching hospitals
NHS Trust

References
1. Ashworth M, Charlton J, Ballard K et al. Variations in antibiotic prescribing and consultation rates for acute respiratory infection in UK general practices 1995-2000. Br J Gen Pract 2005; 55: 603-8.
2. NICE Short Clinical Guidelines Technical Team (2008). Respiratory tract infections – antibiotic prescribing. Prescribing of antibiotics for selflimiting respiratory tract infections in adults and children in primary care. London: National Institute for Health and Clinical Excellence.
3. Woodhead M, Blasi F, Ewig S et al. Guidelines for the management of adult lower respiratory tract infections. Eur Respir J 2005; 26: 1138-80.
4. Braman SS. Chronic cough due to acute bronchitis: ACCP evidence-based clinical practice guidelines. Chest 2006; 129(Suppl. 1), 95S-103S.
5. Lim WS, Baudouin SV, George RC et al. Guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax 2009; 64(Suppl III): iii1-iii55.
6. Smith SM, Fahey T, Smucny J, Becker LA. Antibiotics for acute bronchitis. Cochrane Database of Systematic Reviews 2004, Issue 4. Art No: CD000245. DOI: 10.1002/14651858.CD000245.pub2
7. Dowell J, Pitkethly M, Bain J et al. A randomised controlled trial of delayed antibiotic prescribing as a strategy for managing uncomplicated respiratory tract infection in primary care. Br J Gen Pract 2001; 51: 200-5.
8. Little P, Rumsby K, Kelly J et al. Information leaflet and antibiotic prescribing strategies for acute lower respiratory tract infection: a randomized controlled trial. JAMA 2005; 293: 3029-35.
9. British Infection Association and Health Protection Agency. Management of infection guidance for primary care for consultation and local adaptation. Available at: www.hpa.org.uk/web/HPAwebFile/ HPAweb_C/1279888711402. Produced 2000; Latest Review March-July 2010. Accessed 26 June 2011.
10. Lim WS, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003; 58: 377–82.
11. Schroeder K et Fahey T. Systematic review of randomised controlled trials of over the counter cough medicines for acute cough in adults. BMJ 2002; 324: 329-31.
12. NICE Clinical Guideline 121. Lung cancer: the diagnosis and treatment of lung cancer. 2011. Available at: www.nice.org.uk/guidance/index.jsp?action=byID&o=13465.
13. Edwards C et Stillman P. Minor illness or major disease? The clinical pharmacist in the community. 4th ed. Pharmaceutical Press, London 2006.


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