• Dose and frequency

The dose and frequency of an antibacterial needs to be sufficient to bring drug levels into the therapeutic range. For some antibacterials drug monitoring will be required. 

The appropriate dose will depend on a number of factors, including severity of illness, patient’s age, weight, renal and hepatic function, immune status and previous antibiotic regimen. The BNF and the BNF for Children are good reference sources for checking the appropriate dose and frequency. 

Inadequate dosing can lead to the emergence of resistant strains and treatment failure, while high dosing increases the likelihood of drug-related adverse effects.

• Duration

In primary care the course of treatment is generally decided when the prescription is written. For most infections five to seven days is currently recommended in national guidance. Uncomplicated urinary tract infections can be treated with three days of antibiotics. Tuberculosis requires six months, while treatment for HIV is life-long. To prevent the emergence of resistant strains, prudent prescribing and use of antibiotics is essential. It is important to follow the recommended duration for treatment and avoid prolonged use of antibiotics. This will also prevent the emergence of super infections and lower the risk of toxicity.