Community Acquired Pneumonia (CAP) (Antimicrobial)

What's new / Latest updates

10/10/25 (V4):

added line - For suspected or known Legionnaires Disease, refer to specific guidance here.
Following two significant event reviews in MHDU and ICU, the community-acquired pneumonia guidance has been updated.
- A reminder to explore penicillin allergy information has been added, as beta-lactam antibiotics are the most active agents against Streptococcus pneumoniae, a major cause of CAP.
- Azithromycin has replaced clarithromycin as the preferred macrolide as it has a reduced risk of drug interactions, it can be given intravenously if the patient is unlikely to absorb medication enterally and is less thrombophlebitic.
- In order to provide wider cover for patients in critical care with severe infection, co-amoxiclav has been recommended over amoxicillin, in line with other health boards.
- Additional IV to oral switch information has been provided for severe infection options to optimise oral dosing and activity. Specifically, oral cefuroxime has poor bioavailability and oral doxycycline is appropriate, given the clinical improvement likely at the time of switch to oral therapy.
- Note the duration of treatment is 5 days, unless the patient is not clinically stable.
- Finally, a reminder to explore other options before prescribing levofloxacin due to adverse drug reaction concerns as per MHRA warnings.

BTS 2009
BTS annotated Update 2015
NICE guideline (CG191) Pneumonia in adults: diagnosis and management
For suspected or known Legionnaires Disease, refer to specific guidance here.

Antibiotic therapy in CAP is not dependent on CRP level

START ANTIBIOTICS IMMEDIATELY ONCE THE DIAGNOSIS HAS BEEN MADE

Assess severity using CURB65 score and markers of sepsis. Clinicians without access to a recent blood urea level should use CRB65 score.

CURB65 score is defined by 1 point being scored for each of the following:

Confusion (mental test score 8 or less, new disorientation in person, time or place);
Urea >7mmol/L;
Respiratory rate ≥30/min;
Blood pressure (SBP <90mmHg, diastolic ≤60mmHg);
Age ≥65 years.

Note that CURB65/CRB65 will tend to over-estimate severity of illness in a frail or elderly patient.

For CAP with features of SEPSIS, treat as severe ie CRB65 score 3 to 4 or CURB65 score 3 to 5.

Record CURB65 or CRB65 score in the patient’s medical notes.

CURB65 or CRB65 score identifies those patients that may safely be treated out of hospital. Social support and treatment compliance issues should be considered in addition to CURB/CRB65 score. It is not appropriate to use CURB65 score to assess severity in a post-operative patient as these parameters may already be raised in the immediate post-operative period.

CURB/CRB Score	Severity of illness	Attributable mortality (BTS 2009)
0 to 1	Mild	3%
2	Moderate	9%
3 to 5 OR 2 with features of sepsis	Severe	15 to 40%

There are a number of significant drug interactions with levofloxacin eg warfarin, theophylline; and to a lesser extent with azithromycin: see the BNF for a comprehensive list. Azithromycin and levofloxacin can prolong the QT interval - use with caution in patients with existing QT prolongation or on other drugs known to have this effect: see BNF for more detailed information. Azithromycin can be used with caution in patients on simvastatin as it has a lower risk of rhabdomyolysis (but not zero). In addition to a number of other severe side effects, levofloxacin can lower the seizure threshold and can cause tendon damage (including rupture) occurring within 48 hours of starting treatment or several months after stopping; avoid if there is a history of quinolone-associated tendon damage. The risk of tendon damage increases in patients over 60 years of age and in those taking concomitant steroids. See updated MHRA warnings on fluoroquinolone use published January 2024.

Penicillin allergy

Beta-lactam antibiotics are the most active agents against Strep. pneumoniae. Explore penicillin allergy labels to exclude non-allergy side effects that may allow safe prescription of amoxicillin.

Duration Note

Stop antibiotic treatment after 5 days unless microbiological results suggest a longer course is needed or the person is not clinically stable, for example, if they have had a fever in the past 48 hours or have more than 1 sign of clinical instability (systolic blood pressure less than 90 mmHg, heart rate more than 100/minute, respiratory rate more than 24/minute, arterial oxygen saturation less than 90% or partial pressure of oxygen of more than 60 mmHg in room air).

Consider early intravenous to oral switch with clinical improvement. Duration of therapy includes intravenous and oral treatment.

Remember the risk of tuberculosis, particularly in immunocompromised patients and in travellers or recent settlers from abroad.

For glossary of terms see Glossary.

Drug details

CAP with history of recent foreign travel (discuss with Microbiology/ID consultant, including options for penicillin allergy)

Oral/IV azithromycin 500mg twice daily PLUS oral/IV amoxicillin 1g three times daily