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PatientPlus articles are written for doctors and so the language can be technical. However, some people find that they add depth to the articles found in the other sections of this website which are written for non-medical people.

Blind Treatment Of Infection

If a bacterial infection is suspected, it is often impracticable to wait for tests results before starting treatment. Selecting the 'best guess' antibiotic should be guided by the following principles:1,

  • Use antibiotics responsibly, considering issues such as safety, resistance and cost.
  • Check that an antibiotic is really needed - history and examination may yield clues as to whether condition is bacterial or viral, but this is not always easy. Consider delayed antibiotics. Some viral conditions may need prophylaxis to prevent secondary bacterial overgrowth - e.g. acute necrotising ulcerative gingivitis secondary to herpes simplex infection.
  • Blind prescribing does not obviate the need to take samples for culture and sensitivity, before starting treatment, whenever appropriate. Depending on the clinical picture, this may include skin or wound swabs, high vaginal swabs, urine, faeces, sputum, blood, aspirate. In the hospital environment consider CSF. Where clinically appropriate, consider FBC, ESR, CRP, U E, LFTS, clotting, atypical serology, malaria film, serum for virology, CXR, ABG. Stick test the urine.
  • Blind antibiotic prescribing for unexplained pyrexia is rarely helpful.
  • Calculating dosage is not an exact science but consider factors affecting absorption or bioavailability such as age, weight, hepatic function, renal function, severity of infection and other medication.
  • Underdosing may result in significant failure of treatment and bacterial resistance in serious infection.
  • Excessive dose may result in toxicity, particularly for antibiotics with a narrow margin between the toxic and therapeutic dose (e.g. an aminoglycoside).
  • Consider drug plasma monitoring, although this is difficult in primary care and may be more appropriate in an intermediate care setting.
  • Route of administration - most patients in primary care will cope with oral antibiotics, though some patients have difficulty swallowing tablets and may need liquid or dispersible preparations. Serious infections may require intravenous administration. Avoid intramuscular antibiotics in children as these are likely to be painful.
  • Duration depends on condition and severity. Chronic infections such as TB may require prolonged treatment, UTIs usually require short courses. Follow local policy.
  • Consider any other factors relating to the patient likely to be relevant - e.g. ethnicity, history of allergy, whether immunocompromised, severity of condition, and whether taking other medication.
  • If female:
    • Check whether pregnant, breast-feeding or taking oral contraceptive.
    • In pregnancy avoid tetracyclines, aminoglycosides, quinolones, high dose metronidazole.
    • Short-term use of trimethoprim (theoretical risk in first trimester in patients with poor diet, as folate antagonist) or nitrofurantoin (at term, theoretical risk of neonatal haemolysis) is unlikely to cause problems.
  • Prescribing antibiotics after a telephone consultation should be the exception rather than the rule.
  • Choose simple generics first-line unless there is a very good case for using newer more expensive antibiotics.
  • Avoid widespread use of topical antibiotics, especially those readily used in oral forms, as this may spread resistance.
  • Clarithromycin is an acceptable alternative in patients who get gastrointestinal side effects with erythromycin.
  • If blind treatment fails and test results are not available, check with a microbiologist.
Which Anti-Infective?2

Choosing the right drug in the absence of sensitivity results is an inexact science at the best of time but should be guided by the following principles:

  • History:
    • A detailed history may reveal the source of infection
    • Ask about respiratory, gastrointestinal or genitourinary symptoms.
    • Ask about recent travel or treatment or conditions which could compromise the immune system.
  • Examination - check the temperature and do a systematic examination to detect localising signs.
  • Treatment:
    • After 'best guessing' the source of infection, follow local guidelines.
    • If none exist, use the guidance from the Health Protection Agency (see below).
    • Be ready to change treatment once drug sensitivities are known.
    • Treatment of most infections should not exceed 7 days.
    • In a hospital or intermediate care setting, intravenous antibiotic therapy is usually reviewed after 48 hours and changed to oral preparations when possible.
    • If in doubt, ask a microbiologist.
Management of Infection Guidance for Primary Care from the Health Protection Agency

(brief summary - see HPA site for full guidance.)2

Blind Treatment of Infection

Infection

Treatment

Tonsillitis
  • Most sore throats viral, but if bacterial tonsillitis suspected:
    • Phenoxymethylpenicillin 500 mg BD-QDS
    • If allergic to penicillin, erythromycin 500 mg BD or 250 mg QDS (QDS less side-effects)
Otitis Media in childhood
  • Many viral, resolve without antibiotics.
    If clinically appropriate:
    • Amoxicillin first line - 2-10 yrs 250 mg TDS; over 10 yrs 500 mg TDS
    • Co-amoxiclav 2nd line - 1-6 yrs 156 mg TDS;
    • 6-12 yrs 312 mg TDS

  • If allergic to penicillin:
    • Erythromycin first line - under 2 yrs 125 mg QDS; 2-8 yrs 250mg QDS
    • Azithromycin second line -15-25kg 200 mg OD;26-35kg 300 mg OD;36-45kg 400 mg OD
Rhinosinusitis
  • Reserve antibiotics for severe, or symptoms lasting more than 10 days.
  • First line - phenoxymethylpenicillin or amoxycillin 500mg TDS
  • Second line - co-amoxiclav 625 mg TDS or ciprofloxacin 250 - 500 mg BD plus metronidazole 400mg BD.
Acute bronchitis/LRTI
  • Marginal benefit in healthy adults.
  • Amoxicillin 500mg TDS or oxytetracycline 250-500mg QDS or doxycycline 200 mg stat/100 mg OD for 5 days
Acute exacerbation COPD
  • Most useful where increased dyspnoea and purulent sputum
  • First line - amoxicillin or oxytetracycline 250mg QDS or doxycycline 200 mg stat/100 mg OD for 5 days
  • If allergic to penicillin and tetracyclines C/I erythromycin250 - 500 mg QDS
  • Second line - co-amoxiclav 625 mg TDS
Community Acquired Pneumonia
  • Treated in the community;
    • First line: Amoxicillin 500 mg - 1g TDS
    • No response in 48 hours consider admission or erythromycin 500 mg QDS to cover mycoplasma (rare over 65), add oxytetracycline 250-500 mg QDS or doxycycline 200 mg stat/100 mg OD
    • Severely ill, give parenteral benzylpenicillin prior to admission 1.2G IV.
    • Consider risk factors for Staph aureus and Legionella
Meningitis
  • Admit to hospital immediately
  • Benzylpenicillin prior to admission, unless history of anaphylaxis, (NOT allergy) IV or IM benzylpenicillin
    • Adults and children 10 yr and over: 1200 mg
    • Children 1 - 9 yr: 600 mg
    • Children over 1 yr: 300 mg
Urinary tract infection
  • First line - trimethoprim 200mg/12h PO or nitrofurantoin 50-100mg QDS
  • Second line - depends on susceptibility of organism isolated, e.g. nitrofurantoin, amoxicillin, cefalexin, co-amoxiclav, quinolone, pivmecillinam
Impetigo Topical/oral produce similar results - reserve topical for very localised lesions to obviate resistance.



Document References
  1. Wong SY, Lam MS; Pyrexia of unknown origin--approach to management.; Singapore Med J. 1995 Apr;36(2):204-8. [abstract]
  2. Management of infection Guidance for Primary Care produced by the Health Protection Agency

Internet and Further Reading AcknowledgementsEMIS is grateful to Dr Laurence Knott for writing this article. The final copy has passed scrutiny by the independent Mentor GP and Pharmacy reviewing teams. ©EMIS 2007.
DocID: 454
Document Version: 1
DocRef: bgp328
Last Updated: 17 Apr 2007
Review Date: 16 Apr 2008




















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PS - Health and Poverty

Perhaps the biggest cause of ill health in the world is poverty. Help to Make Poverty History. For example, why not lend some of your money to disadvantaged communities to enable them to trade their way out of poverty through schemes such as Shared Interest.

See also MAKEPOVERTYHISTORY North East for details and links to campaigns against poverty.

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