Pharmacodynamics drug interactions refer to the situation where one drug enhances or weakens the physiological effects or drug effects of another drug, without having a significant impact on the blood drug concentration and pharmacokinetics of the drug.

Generally speaking, the combined application of drugs with the same nature of action can enhance the effect, while the combined application of drugs with opposite nature of action results in weakened efficacy.

Therefore, there are two results of drug efficacy interactions, namely the synergistic effect and the antagonistic effect of drug effects.

Synergistic effect refers to the situation where the combined application of drugs with the same or similar pharmacological effects produces an effect equal to or greater than the sum of the effects produced by the separate application of the two drugs.

Antagonism refers to the situation where the effect produced by the combined application of two drugs is smaller than that of the sole application of one drug.

Sensitization effect on the site of action: When a drug can enhance the sensitivity of a tissue or receptor to another drug, it is called sensitization effect.

Medication for special populations

Special groups refer to pregnant and lactating women, newborns, infants and toddlers, children and the elderly.

The physiological and biochemical functions of special populations are significantly different from those of the general population, and these differences significantly affect the pharmacokinetics and pharmacodynamics of these populations.

If these special groups are treated with drugs according to the conventional dosing regimen, the drugs may not reach a low effective concentration in the body, resulting in treatment failure.

Or toxic reactions occur when the concentration exceeds the low toxic level;

Or it may produce drug effects and adverse reactions that are different from those in the general population.

Only by mastering the pathological and physiological characteristics of these special populations can targeted and rational drug use be carried out in clinical practice to ensure the safety of drug use for these special populations.

Pregnant women should use drugs rationally. For drugs with strong toxic reactions and a narrow safety range, blood drug concentration monitoring should also be conducted.

I. Pharmacokinetic characteristics during pregnancy

During pregnancy, the physiological functions of the mother undergo changes in aspects such as the cardiovascular system, blood system, blood flow, respiratory system, gastrointestinal system, and renal function, thereby altering the in vivo processes and effects of drugs within the mother.

Among them, the changes in plasma albumin concentration, gastrointestinal motility and glomerular filtration rate have a greater impact on pharmacokinetics.

Ii. Influencing Factors of Drug Passage through the Placenta

Drugs in the mother's body need to pass through the placenta to reach the fetus, and drugs or metabolites in the fetus must pass through the placenta to the mother's body and be excreted.

The process by which drugs in the mother's and fetus are transported into each other's bodies through the placenta is called placental drug transport. The main ways of placental drug transport include passive transport, active transport, pinocytosis, and the passage through membrane pores or cellular fissures.

Influencing factors

Placental factors

2. Maternal factors

3. Drug factors

Drug pregnancy toxicity classification:

The U.S. Food and Drug Administration (FDA) assesses the therapeutic benefits of drugs for pregnant women and the potential risks to the fetus based on their teratogenicity to the fetus, and classifies drugs into five grades: A, B, C, D, E, and X.

Grade A

Clinical controlled studies have shown that no drugs have harmful effects on the fetus in the early, middle and late stages of pregnancy, including vitamin A, vitamin B2, vitamin C, vitamin D, vitamin E, sodium levothyroxine, folic acid, pantothenic acid and KCL.

Grade B:

Through animal experiments and studies, no harm to the fetus was found, and there were no clinical controlled trials. Or side effects were shown in animal research experiments, but these side effects have not been confirmed in clinical studies.

Grade C: Animal experiments have shown that it has adverse effects on the fetus and there are no clinical controlled trials. Or no animal and clinical studies have been conducted.

Grade D: Clinical controlled trials or observational trials have sufficient evidence to prove that it is harmful to the fetus, but the therapeutic benefits may outweigh the potential harm.

Grade X: Various experiments have confirmed that it can cause fetal abnormalities. It is contraindicated for women who are entering or about to become pregnant.