GENERAL PRINCIPLES OF PHARMACOLOGICAL THERAPY
Although a large number of specific therapeutic agents are available for treatment of patients with cardiovascular disease, most of these drugs have never been rigorously tested in clinical trials conducted in infants and children with heart disease. Testing in the pediatric population has been included relatively recently as a requirement for gaining Food and Drug Administration approval for a new drug. Even so, most drugs currently used to treat infants with cardiac conditions have not been evaluated with respect to pharmacokinetics, efficacy, or safety in this population.
The number of drugs available to treat cardiovascular disorders is enormous. Rather than attempting to maintain extensive knowledge about each specific drug, it is much more practical to understand principles and mechanisms of action according to drug classification. Practical differences among drugs within a given class are often of minimal clinical significance. A useful approach is to understand general mechanisms of action and to become familiar with one or two specific agents within a given class. In this manner, a small “personal” formulary can be developed that greatly simplifies the amount of information necessary to provide appropriate therapy. It is also important to stay current, be alert to new drug developments, and be willing to modify the approach to drug therapy as new information becomes available.
Drug therapy in infants should be founded on sound principles of clinical pharmacology. Ideally, drug administration is justified only if sufficient data exist to indicate that the overall morbidity or mortality of the disease is reduced by therapy and the beneficial effects outweigh the adverse drug effects. However, information regarding basic and clinical pharmacology of many drugs is simply not available in the neonatal population. Drug therapy for infants with cardiovascular disease is therefore usually extrapolated from studies performed in adult patients or older children and is often guided by personal experience, anecdotal reports, tradition, or uncritical acceptance of drug advertising. Medications are often administered on the basis of personal belief that a drug is effective, sometimes even in the face of scientific evidence to the contrary.
The general concept of rational drug therapy (Table 12-1) is to prescribe drugs in an attempt to maximize efficacy and to minimize adverse drug effects. This implies that therapy is tailored to the needs of a particular patient and clinical situation. Nowhere is this more important than in the newborn population. Adverse or toxic effects of a drug in neonates may not become clear until the drug has been marketed for many years. Even though a drug is commercially available and has been used in adults, it may not be safe or effective in a newborn with heart disease.
TABLE 12-1.Guidelines for Rational Drug Therapy