Paracetamol concentration

Paracetamol, synonym acetaminophen, is world wide probably the most popular analgesic and antipyretic. Its mechanism of action is not well understood. It is not really an NSAID as it is only a very weak inhibitor of cyclo-oxygenase and has hardly any anti-inflammatory activity. For the same reason paracetamol gives only negligible gastrointestinal irritation and gives hardly any blockade of platelet aggregation. Paracetamol concentrations in plasma reach a peak in 30-60 minutes, and the half-life in plasma is about 2 hours. Almost 100% of... 

Activated charcoal may be given as first aid if the patient presents within an hour of ingestion. Antidotal treatment is almost universally effective if administered within 6 hours of overdose. The serum paracetamol concentration measured between 4 and 16 hours determines whether antidotal treatment with acetylcysteine is required, but if a significant overdose has been taken and no result is available by 6 hours after overdose, antidote should be... 

A biomimetic MIP recognition material was devised for determination of a paracetamol (also known as acetominphen) pain reliever using a QCM transducer [109]. To this end, MIP was prepared with two different functional monomers, namely VPD and MAA. An EGDMA cross-linker and AIBN initiator were also present in the solution. The thermo-radical polymerization was performed at 60 °C. The resulting MIP powder was dispersed in a PVC matrix and then drop coated onto a quartz resonator. A linear decrease of the resonant frequency change with the increase of the paracetamol concentration ranged from 50 nM to 10 mM at LOD of 50 nM paracetamol. The chemosensor was successfully applied for the paracetamol determination in real samples, such as human serum and urine. 

Paracetamol concentrations below 50 LLg/ml cannot be measured accurately by this method for such samples a chromatographic method should be used (see below). 

After a single oral dose of 0.9 g to 9 subjects, peak plasma-phenacetin concentrations of 0.2 to 7.4 Lig/ml (mean 2.3) were attained in 1 to 2 hours, and peak plasma-paracetamol concentrations of 3.1 to 11.9 ig/ml (mean 7.9) were attained in 2 to 3.5 hours plasma-phenacetin concentrations were reported to be lower in 9 smokers (E. J. Pantuck et al., Clin. Pharmac. Ther., 1974,15, 9-17). 

Fulminant hepatic failure occurs in 1-5% of cases of paracetamol overdosage 3-6 days after ingestion (71), with frequent deaths in people who take 20-25 g. There is only a narrow margin between the normal maximum 24-hour dosage and that which can cause liver damage and acute hepatic failure. Undoubtedly, some people are more susceptible than most to paracetamol toxicity, since although 6 g has been reported as toxic in some cases, most toxicity is seen with 12 g upwards (72,73). Nomograms have been developed to show the relation between plasma paracetamol concentrations over time and the risk of a serious outcome (SEDA-18, 94). 

Drugs that induce liver microsomal enzymes, such as phenobarbital, phenytoin, carbamazepine, rifampicin, and isoniazid, can make paracetamol poisoning more severe (104,105). In patients taking such drugs the serum paracetamol concentration should be doubled before consulting the usual treatment nomogram. 

We used our specific RIA methods for B, and Bj subunits to investigate the time course of hepatocellular damage in 19 patients admitted with paracetamol overdose (B12, B14). Seven patients had plasma paracetamol concentrations that were below the treatment line and four of these patients had marginal elevations (approximately one and a half times the upper reference limit) of B, upon admission within 4 hr of the overdose. Only one of the seven patients subsequently showed a significant rise in plasma GST B, to nine times the upper reference limit but in this patient and in each of the other seven patients no abnormalities in ALT were found at any time during their hospitalization. 

It is still prudent to consider patients who are alcoholics as being at high risk of hepatotoxicity after a paracetamol overdose, and to treat them with acetylcysteine. Some workers have questioned the use of a lower plasma-paracetamol concentration threshold for the treatment of paracetamol poisoning in alcoholics, but most advocate treatment at the lower threshold. Possible malnutrition and fasting in these patients would further support the need for such treatment. ... 

Kennedy JM, TyersNM, Davey AK. The influence of morphine on the absorption of paracetamol from various formulations in subjects indie supine position, as assessed by TDx measurement of salivary paracetamol concentrations. JPharmPharmacol(200y) 55,1345-50. 

While studying solutions of paracetamol by cathetometric method it can be observed that in Ctst dilutions by 100 times (paracetamol concentrations being 10 -... 

Community in given structures may be assumed taking into account coincidence of waves length and values of optical density for solutions with concentrations 10 , and 10 mole/1. Gradual reduction of paracetamol concentration in solutions is not accompanied by the same reduction of optical density value. Growth of absorption in comparison with more concentrated solutions is observed for solutions with concentrations 10 , 10and 10 mole/1 (Table 3). All this allows to assume the rise of stmctural changes in these solutions. ... 

In a prospective observational study, opiates reduced serum paracetamol concentrations at 4 hours after ingestion compared with concentrations after paracetamol alone [185 ]. 

It frequently happens that two methods of analysis are compared by studying test samples containing different amounts of anal) e. For example. Table 3.1 gives the results of determining paracetamol concentration (% m/m) in tablets by two different methods. Ten tablets from 10 different batches were analysed in order to see whether the results obtained by the two methods differed. 

These values have mean d = 0.159 and standard deviation s,= 0.570. Substituting in equation (3.6), with n = 10, gives t=0.88. The critical value is tg = 2.26 ( = 0.05). Since the calculated value of t is less than this, the null hypothesis is not rejected the methods do not give significantly different results for the paracetamol concentration. 

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