Physical disabilities such as low vision, arthritis in the hands, or difficulty swallowing can also affect drug — or drug formulation or packaging — choices. For example, people with low vision who need insulin may find it easier to use an insulin pen than a syringe. People who have difficulty opening pill bottles or manipulating a blood glucose meter because of hand problems may need to seek out alternative pill packaging or devices that help open packages and meters and lancing devices with rubber, “easy-grip” features.
Other drugs already being taken. Drug interactions are a major issue when prescribing a new drug. Drug interactions can produce exaggerated effects when multiple drugs are given to achieve the same goal. It’s also possible for one drug to block the metabolism of another drug, resulting in excessive blood levels of the drug whose metabolism is blocked. In a third possibility, one drug can prevent another drug from doing its job. For example, NSAIDs (such as Motrin) prevent aspirin from inhibiting platelet function when taken at the same time.
Age. Very young age and very old age must be considered when prescribing a drug. That’s because kidney and liver function may be lower or diminished in these age groups, so drugs may not be metabolized at the rate expected. In addition, premature infants have a lower body weight than other newborns, and elderly people may also have a low body weight, meaning they need less of a drug than a heavier person.
Age is also considered when deciding how aggressively to manage certain conditions. For example, the cholesterol goals for a 90-year-old may not need to be as low as for a 50-year-old, and therefore therapy for the 90-year-old is less aggressive.
Body size or weight. For children, drug dosing is often done according to body weight. In adults, many oncology [cancer] drugs are dosed based either on body weight or on body surface area (using an equation that takes height and weight into account). The amount of insulin a person needs can also be affected by weight: When weight is gained, an increased dose may be needed, and if weight is lost, less insulin may be necessary to maintain blood glucose in target range.
Some medical professionals have argued that certain other classes of drugs, such as antibiotics, should also be dosed based on body size for adults, based on data showing that obese people may respond differently to some drugs than people of lower weight.
However, this is a medical issue that has yet to be thoroughly researched.
Profession or daily activities. Many drugs can reduce concentration or cause sleepiness, which can be a big problem for people who need to operate machinery or drive. For these people, doctors attempt to prescribe the least-sedating drugs. For example, to treat allergies, nasal steroids or antihistamines that are less sedating may be prescribed in place of antihistamines such as diphenhydramine (brand name Benadryl), which is known to cause sedation.
Side effects. All drugs have side effects, but sometimes a person develops such severe or intrusive side effects that an alternative must be sought. This can happen soon after a person starts a drug, but in some cases it happens after a person has been using a drug for a long time with no complaints. As noted earlier, a change in kidney or liver function can affect how a person’s body processes a drug, possibly resulting in the onset of side effects. Weight loss can also reduce the amount of a drug a person needs and lead to new side effects if the dose is not reduced. But many times the reason for late-onset side effects is unknown.
Ability to pay. In an ideal world, a person’s ability to pay for a therapy (or his insurance coverage for it) would not be a consideration. Physicians would simply prescribe what is best for the person regardless of cost. But in today’s world, that’s not the way it usually works. To save you out-of-pocket costs, your doctor may prescribe a generic drug or the brand-name drug favored by your health insurance plan. Generic drugs have the same active ingredients as brand-name drugs and should provide equally effective treatment. When no generic is available, your doctor may be able to choose from several drugs in the same class, which have similar effects but may be sold for different prices or require different co-payments.