Pregnant and lactating women take medications. Medications can pass through the placenta and breast milk, making fetuses and infants unintentional drug users. Improper medication can cause serious harm.
In order to ensure the safety of mothers and infants, when formulating the dosage regimen, attention should be paid to the pharmacokinetics and pharmacodynamics characteristics of the pregnant mother, fetus and newborn, and the appropriate dosage and timely administration of medication should be taken.
1. Pharmacokinetic characteristics during pregnancy
(1) Pharmacokinetics of drugs in the pregnant mother
Throughout pregnancy, the mother, placenta , and fetus form a biological and pharmacokinetic whole.
After the mother takes medication, the drug not only exists in the mother's body, but can also enter the fetus through the placenta and affect the fetus.
attaches great importance to the rational use of drugs during pregnancy, which is very important to protect mother and baby.
During pregnancy, the mother's physiological functions will undergo various changes, thereby changing the process and effects of drugs in the mother's body.
For drugs with serious side effects and narrow safety range, plasma drug concentration should be monitored.
1. Drug absorption
In the early and middle stages of pregnancy, due to the influence of progesterone, gastric acid secretion is reduced, gastric emptying is delayed, intestinal motility is weakened, and the absorption of oral drugs is delayed, the peak time is prolonged, and the peak concentration is reduced.
2, drug distribution
3, drug metabolism
During pregnancy, the metabolism of drugs is enhanced. This is related to the increase in progesterone concentration during pregnancy, which causes an increase in the activity of liver microsomal drug hydroxylase. For example, phenytoin is hydroxylated in pregnant women. The process is significantly sped up.
4. Drug excretion
During pregnancy, osmotic blood flow increases by 25% to 50%, glomerular filtration rate increases by 50%, which accelerates the elimination rate of many drugs, especially drugs that are mainly excreted by the kidneys.
(2) The process of drugs in the fetus
Each organ and function of the fetus is in the development stage, and the drug process in the fetus is different from that of adults and has its own characteristics.
1. Drug absorption
Drugs in the mother need to pass through the placenta to reach the fetus. Drugs or metabolites in the fetus must also pass through the placenta to the mother and be excreted.
2. Drug distribution
Fetal liver and brain organs are relatively large and have large blood flow. After the drug enters the umbilical vein, about 60% to 80% of the blood flow enters the liver, so the drug is distributed more in the liver.
The fetal blood-brain barrier is not fully developed, and drugs can easily enter the central nervous system .
3. Drug metabolism
The fetus has limited ability to metabolize drugs.
4. Drug excretion
The fetal glomerular filtration rate is very low, and the renal drug excretion function is extremely poor.
5. Effects of drugs on fetuses at different stages of pregnancy
Fetuses at different stages of development have greatly different sensitivity to drugs.
