Prescribing empirical and broad-spectrum antibiotics

The use of antibiotics in day to day practice for the patient with community-acquired or hospital-acquired infections is often empirical, as the results of culture and sensitivity or specific diagnostic tests are still awaited.  This is especially true for infections in critically ill patients where the urgency of situation demands empirical treatment.

Broad spectrum antibiotics are typically selected for empiric therapy as the aim is to cover as many etiopathogens as possible that are usually associated with that particular clinical presentation. They are initiated as soon as specimens are collected.

The word empirical is derived from the Greek word “empeiria”, which means experience. Therefore, empirical treatment literally means “based on observation or practical experience rather than theory”.

Stedman’s Medical Dictionary gives the meaning of the word empirical as “Founded on practical experience rather than on reasoning alone but not proved scientifically in contrast to rational”.

Goodman & Gilman’s The Pharmacological Basis of Therapeutics (10th Edn) states: “Empiricism often is defined as the practice of medicine founded on mere experience, without the aid of science or a knowledge of principles.” But, it has also observed that “The connotations of this definition are misleading; empirical observations need not be scientifically unsound.”

Broad-spectrum antibiotics run the risk of drug-resistant infections. Therefore, they should be tapered to a more targeted therapy once the culture reports are available.

The list of CDSCO approved drugs includes two broad spectrum antimicrobials: Doxycycline and cephalexin (https://cdscoonline.gov.in/CDSCO/Drugs).

Both doxycycline and cephalexin are broad spectrum antibiotics. Cephalexin is usually used as preoperative prophylaxis for prevention of surgical site infections.

Doxycycline is an inexpensive and time tested drug. It has low potential for developing resistance; in addition, it has antiviral and anti-inflammatory properties. Doxycycline is the drug of choice for scrub tyhus and for rickettsial infections. It is also an effective treatment of leptospirosis. This spectrum of coverage makes it an appropriate empiric antibiotic, especially in our Indian setting where scrub typhus is now an important cause of febrile illness.