Classification and generations of drugs
In modern clinical practice, these medications are divided into two main categories:
- 1st generation: includes compounds such as carbutamide, tolazamide, tolbutamide, and chlorpropamide.
- 2nd generation: is represented by modern medications, among which are glibenclamide, gliclazide, glipizide, and gliquidone.
Today in medical practice, there is a clear trend: priority is given to second-generation drugs due to their efficacy and safety profile.
Mechanism of blood glucose-lowering action
The pharmacological effect is complex in nature, but the main component is the stimulation of endogenous insulin secretion. The pancreatic mechanism is implemented through the following sequence:
- The drug binds to a specific receptor (mass 140 kDa) on the membrane of the β-cell of the islets of Langerhans.
- ATP-sensitive $K^+$ channels are blocked, which stops the efflux of potassium ions.
- Potassium retention causes depolarization of the cell membrane.
- Voltage-gated $Ca^{2+}$ channels open, and calcium ions rapidly rush into the cytoplasm.
- An increase in calcium concentration triggers insulin exocytosis.
In addition, there are extrapancreatic and sensitizing effects: the sensitivity of β-cells to glucose is restored, the density and affinity of insulin receptors in tissues increase, and intracellular signal transduction is improved.
Pharmacokinetics and safety
Drugs of this group have important features of interaction with the body:
- Appetite: can stimulate appetite, which is considered an undesirable side effect during strict dietary control of diabetes.
- Protein binding: characterized by a high degree of binding to plasma albumin, which creates a risk of drug interactions with NSAIDs and indirect anticoagulants competing for protein binding sites.
- Pregnancy: active substances cross the placental barrier, so their prescribing during pregnancy requires increased caution.
Issues and risks of therapy
Long-term use of sulfonylureas is associated with a number of clinical difficulties:
- Selectivity issue: potassium channel blockade affects not only the β-cells of the pancreas, but also cardiomyocytes and angiocytes. Over time, this may increase the risk of cardiovascular mortality.
- Secondary resistance phenomenon: in some patients, a decrease in the therapeutic efficacy of drugs develops against the background of regular three-year therapy.
Briefly: answers to topical questions
What side effects are characteristic of sulfonylurea derivatives?
Characteristic side effects of sulfonylurea derivatives include hypoglycemia, increased appetite, and weight gain.
- Hypoglycemia is the main risk of therapy, the probability of which increases significantly with age.
- Weight gain is an undesirable effect, as diabetes treatment requires strict dietary control.
- Cardiovascular risks — with long-term use, the risk of cardiovascular mortality increases due to non-selective blockade of potassium channels in cardiomyocytes and angiocytes.
Also, in some patients after 3 years of regular therapy, secondary resistance develops.
What are the absolute contraindications to prescribing sulfonylurea derivatives?
Sources list ketoacidosis, hepatic impairment, pregnancy, and lactation as contraindications for sulfonylureas; renal impairment is also indicated as a contraindication, but for gliclazide, glimepiride, and gliquidone, use with caution or dose adjustment is permitted.
The drugs cross the placental barrier, so prescribing during pregnancy requires caution. In acute coronary syndrome, the use of glibenclamide should be avoided.
What are the elimination pathways of sulfonylurea derivatives from the body?
For glimepiride, elimination pathways include the kidneys and intestines.
The drug is metabolized in the liver to form two types of active metabolites — carboxylated and hydroxylated. Metabolites are excreted by the kidneys and through the intestines. The half-life of glimepiride is 5–8 hours.
Class and exam questions
What is the main pancreatic mechanism of action of sulfonylureas?
The drug binds to the receptor on the β-cell membrane, blocks ATP-sensitive potassium channels, causes membrane depolarization, the opening of calcium channels, and exocytosis of endogenous insulin.
Why can sulfonylurea drugs cause drug interactions?
They have a high degree of binding to plasma albumin, due to which they can compete for proteins with other agents, for example, NSAIDs or indirect anticoagulants.
What is the selectivity problem of these drugs?
The drugs block potassium channels not only in the pancreas, but also in blood vessels (angiocytes) and the heart (cardiomyocytes), which increases cardiovascular risks with long-term use.
What is secondary resistance?
This is a decrease in the therapeutic efficacy observed in some patients after three years of regular intake of sulfonylurea drugs.
What else to study on this topic
- Full list of 1st generation drug representatives
- Full list of 2nd generation drug representatives
- Extrapancreatic effects and post-receptor signal transduction level
- Features of drug penetration across the placental barrier
- Effect of potassium channel blockade on cardiomyocytes and angiocytes
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