N-acetyl cysteine (NAC) is an important medication used to treat paracetamol poisoning. It works by replenishing glutathione levels in the liver, which helps to detoxify the harmful metabolite of paracetamol. NAC is typically administered intravenously in a hospital setting.
The dosing of NAC in paracetamol poisoning is based on the patient's weight and the severity of the overdose. The standard dose regimen involves a loading dose of 150 mg/kg body weight given over 1 hour, followed by a maintenance dose of 50 mg/kg over 4 hours, and then 100 mg/kg over 16 hours. This regimen provides a total dose of 300 mg/kg over 21 hours.
It is important to note that NAC should only be administered under the supervision of a healthcare professional. Early administration of NAC is crucial in preventing liver damage in cases of paracetamol poisoning.
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| Dosing of N acetyl cysteine |
Markers for GFR measurement:
Several drugs and endogenous substances have been used as markers to measure GFR. These markers are carried to the kidney by the blood via the renal artery and are filtered at the glomerulus.
Several criteria are necessary to use a drug as a marker to measure GFR:
1. The drug must be freely filtered at the glomerulus.
2. The drug must neither be reabsorbed nor actively secreted by the renal tubules.
3. The drug should not be metabolized.
4. The drug should not bind significantly to plasma proteins.
5. The drug should neither have an effect on the filtration rate nor alter renal function.
6. The drug should be nontoxic.
7. The drug may be infused in a sufficient dose to permit simple and accurate quantitation in plasma and in urine.
Therefore, the rate at which these drug markers are filtered from the blood into the urine per unit of time reflects the GFR of the kidney. Changes in GFR reflect changes in kidney function that may be diminished in uremic conditions.
Inulin, a fructose polysaccharide, fulfills most of the criteria listed above and is therefore used as a standard reference for the measurement of GFR. In practice, however, the use of inulin involves a timeconsuming procedure in which inulin is given by intravenous infusion until a constant steady-state plasma level is obtained. Clearance of inulin may then be measured by the rate of infusion divided by the steady-state plasma inulin concentration. Although this procedure gives an accurate value for GFR, inulin clearance is not used frequently in clinical practice.
The clearance of creatinine is used most extensively as a measurement of GFR.
Creatinine is an endogenous substance formed from creatine phosphate during muscle metabolism. Creatinine production varies with age, weight, and gender of the individual. In humans, creatinine is filtered mainly at the glomerulus, with no tubular reabsorption. However, a small amount of creatinine may be actively secreted by the renal tubules, and the values of GFR obtained by the creatinine clearance tend to be higher than GFR measured by inulin clearance.
Creatinine clearance tends to decrease in the elderly patient. As mentioned in Chapter 22, the physiologic changes due to aging may necessitate special considerations in administering drugs in the elderly.
Measurement of blood urea nitrogen (BUN) is a commonly used clinical diagnostic laboratory test for renal disease. Urea is the end product of protein catabolism and is excreted through the kidney.
Normal BUN levels range from 10 to 20 mg/dL. Higher BUN levels generally indicate the presence of renal disease. However, other factors, such as excessive protein intake, reduced renal blood flow, hemorrhagic shock, or gastric bleeding, may affect increased BUN levels. The renal clearance of urea is by glomerular filtration and partial reabsorption in the renal tubules. Therefore, the renal clearance of urea is less than creatinine or inulin clearance and does not give a quantitative measure of kidney function
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