General Guidelines

Antimicrobial medicines are the most over-used class of medicines worldwide including Zimbabwe. It has become a global concern that we are reaching the post-antibiotic era where common bacterial infections are no longer treatable with common antibiotics. Apart from the unnecessary cost and risk to the patient, overuse encourages development of resistant organisms, a problem that has proven serious and expensive in many countries. In many cases antimicrobial medicines are given "blindly" or "empirically", based on clinical suspicion without microbiological confirmation. Antimicrobials should be used only in patients with likely bacterial illness requiring systemic therapy. Positive identification of the pathogen and anti-microbial susceptibility testing should be sought wherever possible as this will result in improved and more cost-effective treatment outcome.

Principles of antimicrobial use

1. Choice of agent should be based on factors such as spectrum of activity, anticipated efficacy, safety, previous clinical experience, cost, and potential for resistance. These are influenced by the severity of illness and whether the medicine is to be used for prophylaxis, empirical therapy or therapy directed by identification of one or more pathogens.

2. Prophylactic therapy should be restricted to the use of a limited range of agents of proven efficacy in invasive procedures with a high risk of infection or where the consequences of infection are disastrous. Most surgical prophylaxis should be parenteral and commence just before the procedure, continuing for no more than one or two doses after the end of the operation. The aim is to achieve high plasma and tissue levels at the time that contamination would likely occur i.e. during the operation.

3. Empirical therapy should be based on local epidemiological data on potential pathogens and their patterns of antibiotic susceptibility. Appropriate specimens for Gram strain, culture and sensitivity testing should be obtained before commencing antimicrobial therapy. Maintaining a database of susceptibility profile is useful as a guide for appropriate choice of empirical therapy which is based on local, regional and national patterns.

4. Directed antimicrobial therapy for proven pathogens should include the most effective, least toxic, narrowest spectrum agent available. This practice reduces the problems associated with broad spectrum therapy, that is, selection of resistant micro-organisms and super-infection.

5. Choice of route of administration should be determined by the site and severity of infection. For mild to moderate infections the oral route is preferred, whilst the parenteral route should only be used for severe infections. It is also important that topical antimicrobial therapy be restricted to a few proven indications, for example, eye infections because of the capacity of most agents to select for resistant micro organisms and to cause sensitisation.

6. Antimicrobial combinations have few indications. These include:

to extend the spectrum of cover, for example, in empirical therapy or in mixed infections
to achieve a more rapid and complete bactericidal effect, for example, in enterococcal endocarditis
to prevent the emergence of resistant micro-organisms, for example, in the therapy of tuberculosis

Note: Doses given are for a 70kg adult with normal hepatic and renal function. Paediatric doses are given in the chapter on Paediatric Conditions. In the elderly, as a general rule, doses given could be lower than recommended adults doses (see Chapter on medicines and the Elderly in main Zimbabwe STG)

7. Access, Watch, Reserve Principles (AWaRe)

To improve the quality of hospital antibiotic use, the selection of antibiotics was guided by the WHO Essential medicines List Access, Watch and Reserve (AWaRe) classification.

Access: Which indicates the antibiotic of choice for each of the 25 most common infections. These antibiotics should always be available, affordable and quality assured.

Watch: Which includes most of the "highest-priority critically important antimicrobials" for human medicine and veterinary use. These antibiotics are recommended for specific and limited conditions.

Reserve: Antibiotics that should only be used as a last resort when all other antibiotics have failed.