Experimental measurement of pharmacokinetic parameters of sulfonamides
Sulfonamides can react with certain reagents to form colored substances, and their blood concentrations can be quantified by colorimetry. In acidic environments, the amino group (-NH2) on the benzene ring of sulfonamides is ionized to form ammonium (-NH3+) compounds, which undergo diazotization with sodium nitrite to form diazonium salts (-N=N+-). This compound is colorimetric at 525 nm, and its optical density is proportional to the concentration of the sulfonamide drug.
Operation method
colorimetric method
Principle
Sulfonamides can react with certain reagents to form colored substances, and their blood concentrations can be quantified by colorimetry. In acidic environments, the amino group (-NH2) on the benzene ring of sulfonamides is ionized to form ammonium (-NH3+) compounds, which undergo diazotization with sodium nitrite to form diazonium salts (-N=N+-). This compound is colorimetric at 525 nm, and its optical density is proportional to the concentration of sulfonamides. Pharmacokinetics: the study of the kinetic patterns of drug transport and conversion in the body. By observing the changes in blood concentration after drug administration (time-volume curve), the rate of drug elimination from plasma is studied, and the law is described by atrial and ventricular modeling, which guides the clinical use of the drug, the adjustment of drug dosage and dosing intervals.
Materials and Instruments
Rabbit Move 1. Anesthesia, isolation of the carotid artery. After anticoagulation with heparin injected intravenously at the ear margin, the carotid artery is cannulated and arterial blood is taken for backup. Caveat 1. The same pipette is used to take the blood sample, so a blank blood sample should be taken first and added to the control tube and the standard tube respectively, and then the blood sample should be taken from 90 min after injection, followed by the blood samples of 60, 45, 30, 15, 5, 3 and 0 min after injection. 2. In each test tube, add trichloroacetic acid first, then add the blood sample, and shake immediately after adding the blood sample, otherwise coagulation will occur quickly, affecting the accuracy of the results. 3. The order of color developer must not be wrong: sodium nitrite → muscimol. 4. The unit of blood concentration of SD is μg/ml. For more product details, please visit Aladdin Scientific website.
Trichloroacetic acid, Sodium nitrite, Muscimol, Sulfadiazine
Spectrophotometer
2. Blood sampling: blank arterial blood was taken first. Then sulfadiazine (SD, 0.3 g ) was injected intravenously into the ear margin of rabbits, and arterial blood was taken at 0, 3, 5, 15, 30, 45, 60 and 90 min after the injection, respectively.
3. Determination of blood concentration: The drugs were added strictly in the order shown in the table below:
According to the drug concentration of the standard tube and its optical density value, the drug concentration in the sample tube can be calculated. The formula is as follows:
OD sample/OD standard = C sample/C standard
The measured blood drug concentration value and time are curve-fitted by computer to obtain the drug-time curve, expressed by the following formula:
Ct = Ae-αt + Be-βt
where.
Ct: blood concentration after time t
A: blood drug concentration at the start of distribution;
α: distribution rate constant;
B: blood drug concentration at the onset of elimination;
β: elimination rate constant.
The time-volume graph was plotted on semi-logarithmic coordinate paper with time (t) as the horizontal coordinate and the logarithm of the blood concentration converted from the measured optical density value as the vertical coordinate.