Initial therapy is usually empirical; and the regimen is adjusted according to the results of culture and sensitivity testing. Physicians must select a drug, administration route, dosage, and dosing interval. These may be changed several times during therapy. For example, severe nausea and high severity of illness may necessitate initial par-enteral antibiotic administration. Several days later, when the nausea has abated and the patient is clinically stable, the patient may be switched to oral chemotherapy. Such an adjustment of therapy reduces the length of hospital stay while providing effective, safe treatment.
Once a chemotherapy regimen has been selected, the next step in managing chemotherapy is to define the outcome measures that will define therapeutic success and those that will define unacceptable toxicity and necessitate discontinuation of the chosen drugs. For example, resolution of fever and purulent sputum production, normalization of the white blood cell count, reversal of tachypnea and hypoxia, and improvement of constitutional signs and symptoms may be selected as measures that will be used to evaluate whether treatment of pneumonia is successful.
Often treatment must be continued for several days after objective signs and symptoms of infection have resolved. Patients should be instructed to continue antibiotics for the full duration indicated, even if they feel better. If the patient's recovery is delayed from what is reasonably expectable, the diagnosis should be reconsidered.
Many patients receive lengthy courses of antibiotics that probably should not have been started. More than half of courses of antimicrobial chemotherapy are inappropriate. Influenza pneumonia and viral upper respiratory infections, for example, are impervious to assault by antibiotics, although many patients with these illnesses receive such antibiotics. Of course, influenza may be complicated by postinfluenzal staphylococcal pneumonia, for which antibiotics are indicated. Careful sequential evaluation of seriously ill patients for whom antibiotics are deferred is as important as in patients for whom antibiotics are prescribed.
^ Study Questions
1. Choose the best answer. Selective toxicity is
(A) What the drug does to the patient
(B) What the patient does to the drug
(C) What the pathogen does to the patient
(D) What the drug does to the pathogen
(E) What the pathogen does to the drug
2. A 60-year-old patient with AIDS presents to the emergency department with a temperature of 102°F, confused, and is going in and out of consciousness. He exhibits rapid respiration and a blood pressure of 80/40. You determine that both the sputum and urine are negative by Gram staining. Which of the following is the best choice?
(A) Administer penicillin G intravenously.
(B) Administer vancomycin.
(C) Administer clindamycin and amikacin.
(D) Send a clinical sample to laboratory to find out what the organism is before treating.
3. The term magic bullet was coined for
(A) Ehrlich discovering the drug salvarsan for the treatment of syphilis
(B) Fleming discovering the antibacterial effect of penicillium notatum
(C) Florey showing the effectiveness of penicillin in patients
(D) Wilson discovering the broad spectrum antibiotic streptomycin
4. Choose the best answer for the following. The emergence of microbial antibiotic drug resistance
(A) Requires the concurrent administration of more than one antibiotic
(B) Is a direct result of the use of antibiotics in livestock
(C) Is a problem that was overcome by the development of vancomycin
(D) Is due in large part to the indiscriminate use of antibiotics in humans
5. A patient refuses to continue to take erythromycin because it makes him vomit. This is an example of which patient-drug-pathogen interaction?
(E) Selective toxicity
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