Narrowing the choices
For any treatment regimen, the unique requirements of the individual person need to be considered. Here are some of the main things doctors consider when prescribing drugs for any condition, including diabetes.
Allergies. An allergy to a medicine usually prohibits the use of that medicine or sometimes the use of an entire class of medicines. True allergies are due to an immune-based reaction and typically cause such symptoms as skin rashes, itching, wheezing, and tissue swelling. Before prescribing a new drug, doctors ask if a person has any known drug allergies.
Pregnancy or breast-feeding. When a woman is pregnant or breast-feeding, the potential effects of any therapy on the fetus or newborn must be considered. Only medicines that are clearly needed and have an acceptable balance of benefit (to the mother) and risk (to the fetus or newborn) should be prescribed.
The Food and Drug Administration currently classifies drugs in categories A, B, C, D, and X, with A being shown to be safe during pregnancy, and X being a drug that is known to harm human fetuses. Drugs in categories B, C, or D have varying levels of evidence one way or the other. The FDA is currently revising this labeling system to make the information on risks clearer.
The usual blood-glucose-lowering drug of choice during pregnancy is insulin, regardless of the type of diabetes a woman has (Type 1, Type 2, or gestational). However, most retrospective studies and published clinical experiences on the use of oral diabetes medicines during pregnancy have not shown an increased risk of birth defects. Women who currently take oral diabetes drugs and are planning a pregnancy are advised to discuss their options with their doctor.
Other medical conditions. Certain medical conditions can influence drug choices. For example, abnormalities in stomach acidity or small bowel disease may decrease drug absorption, possibly limiting the therapeutic options for people with these conditions.
When a person with diabetes requires treatment for another medical condition, the effect of the treatment on his blood glucose level is an important consideration. Some drugs are known to raise or lower blood glucose levels, or to make the symptoms of low blood glucose less noticeable, and these drugs may need to be avoided or used with caution.
Kidney and liver function. The two major organs involved in drug metabolism are the liver and the kidney, so tests to evaluate how well they are functioning are sometimes done before starting a new drug. Evaluating the kidney’s degree of functioning is commonly done with a serum [blood] creatinine test. Normally, the kidney removes creatinine from the blood, so the higher the blood level of creatinine, the lower the kidney function. There are no good tests to evaluate liver function, but physicians look at blood tests of liver enzymes and bilirubin to get some idea.
It’s worth noting that kidney and liver function can change over time and typically diminish with age. When this happens, these organs cannot process and eliminate drugs from the body the way they once did, and drugs can build up to dangerous levels in the blood (a condition called drug toxicity). This is a common reason people who take insulin start developing hypoglycemia even when they haven’t changed their usual dose of insulin: The kidneys are responsible for eliminating insulin from the body, but when they aren’t working as well, the insulin stays in the body longer, leading to hypoglycemia.
Physical or mental disabilities. Certain drugs such as sedatives and antidepressants may worsen the ability to think clearly or to remember things, or they may cause outright confusion. They would therefore be avoided in people already experiencing thinking or memory problems, such as those believed to have early Alzheimer disease. Many other drugs, including some common over-the-counter therapies may also cause confusion.