SINCE World War II, medical science has progressed to a stage where competitive medications are available to treat the same ailment in different people. This is not just about brands (which is a trade issue) but generic drugs (which is a scientific issue). In this report, we shall look at the various factors that decide the selection of a particular drug.
Safety: The following sub-criteria must be considered under the criterion of safety:
* Acute therapeutic index: If the patient’s condition is acute, how effective is a particular drug even if it has certain side-effects as long as the acuteness of the condition is lowered? Example: narcotic pain-killers are very effective in healing pain but come with the potential side-effect of addiction.
* Long-term safety: A medication may be safe in short-term treatment, but how safe it is in long-term treatment? Example: antibiotics are acceptable in short-term treatment, but can have undesirable effects in case of prolonged use.
* Drug-drug interaction risk: Drugs are chemicals, and many chemicals react to produce a different chemical, which has an effect that may harm the patient or aggravate his/her condition. Example: A tricyclic anti-depressant and alcohol interact to produce a new condition that warrants separate treatment.
Drug-drug interaction risk is of two types:
· Pharmacokinetic: In this type of drug-drug interaction, two drugs, independent of each other, have certain effects on one or more body processes (e.g., metabolism) that affects the performance of the other. Example: Darvocet-N (propoxyphene and acetaminophen) inhibits the action of a liver enzyme that Lexapro (escitalopram) depends on for its metabolism. This causes an increase in the side-effects of Lexapro.
· Pharmacodynamic: Here, two or more drugs actually produce the same effect on the same organ, thus increasing the total, added effect. Example: Lexapro has certain side-effects such as drowsiness and fatigue. Darvocet-N also acts similarly on the brain. Thus, the side-effects of both the drugs are more intense.
Tolerability: A drug may be effective but not tolerable by all patients. Example: Allergies to certain drugs in some people. Short-term and long-term tolerability have to be taken into account. Efficacy: A drug is not equally effective in all patients. For example, some patients with depression or anxiety disorders experience relief from escitalopram, but there are many who don’t, who therefore have to be prescribed a different anti-depressant. The rate of onset of therapeutic action is an important factor to be considered too.
Cost: Cost does not mean the cost of purchase of a certain medicine alone. It should also cover the cost of treatment of a complication that may arise from using a different drug. Example: In a person who insists on taking alcohol and yet needs to be treated for depression is usually administered an SSRI drug because these drugs don’t potentiate the effects of alcohol, whereas another group of anti-depressants (such as tricyclics) can cause a new problem in such patients, which would require a different and expensive treatment. Therefore, it’s better to prescribe the more expensive escitalopram instead of a cheaper tricyclic in such patients.
Simplicity of treatment: The simplest mode of administration is preferred. If there is a choice between an injection and oral administration, the latter is preferred if the efficacy of both the modes is comparable. Or, local application is preferred to the oral route where possible; e.g., antibiotic treatment of eye infections. Dosage and frequency of administration too are an important factor to decide simplicity of treatment.
To summarize, not all medicines with the same composition are equally effective on all patients with the same ailment. Safety, tolerability, efficacy, cost, and simplicity are the issues to be considered. Most doctors go by their own experience with past patients and change prescription only if it is not working on specific patients. This is because it is not possible (or too cumbersome) to perform tests to judge the suitability of specific drugs on each patient before prescribing, though such tests are performed in cases where incompatibility can lead to very serious side-effects.