The Study of Salicylate Pharmacokinetics in Intoxicated Infants and Children

Novel absorbance peak of gentisic acid following the oxidation reaction

Gentisic acid (GA), a metabolite of acetylsalicylic acid (ASA), and homogentisic acid (HGA), which is excreted at high levels in alkaptonuria, are divalent phenolic acids with very similar structures. Urine containing HGA is dark brown in color due to its oxidation. We recently reported a new oxidation method of HGA involving the addition of sodium hydroxide (NaOH) with sodium hypochlorite pentahydrate (NaOCl·5H2O), which is a strong oxidant. In the present study, we attempted to oxidize GA, which has a similar structure to HGA, using our method. We herein observed color changes in GA solution and analyzed the absorption spectra of GA after the addition of NaOH with NaOCl·5H2O. We also examined the oxidation reaction of GA using a liquid chromatography time-of-flight mass spectrometer (LC/TOF-MS). The results obtained indicated that GA solution had a unique absorption spectrum with a peak at approximately 500 nm through an oxidation reaction following the addition of NaOH with NaOCl·5H2O. This spectrophotometric method enables GA to be detected in sample solutions without expensive analytical instruments or a complex method.

Salicylate Intoxication

A review of pathology, corrective measures, and incidence of salicylate poisoning is presented.

A composite patient case (developed to illustrate symptomatology of salicylism) demonstrates a wide range of signs and symptoms. Subsequent discussion of supportive and corrective measures emphasizes correction of the acid-base, and fluid and electrolyte imbalance associated with salicylate poisoning. Treatment is considered within the context of both moderate and severe poisoning; recently developed and traditional procedures are reviewed.

Treatment of fever in childhood

Although the need for routine antipyretic therapy in children has often been questioned, there are no data to contra-indicate this. Not all fevers need to be treated but many physicians do so to relieve parental concern. The most commonly used antipyretic drugs are acetylsalicylic acid (ASA), paracetamol (acetaminophen) and dipyrone (metamizol). Paracetamol and ASA have been extensively evaluated but there are few clinical trials on dipyrone. In the last decade a strong statistical association has been observed between salicylates and Reye syndrome. Paracetamol is the most common cause of acute hepatic failure. Dipyrone has been associated with agranulocytosis. In the light of these findings the extensive use of antipyretics drugs has been seriously questioned.

Pediatric gastrointestinal decontamination in acute toxin ingestion

The appropriate implementation of the various modalities of gastrointestinal (GI) decontamination is critical in the management of the pediatric patient who is examined in the emergency department or private office after an acute ingestion. Gastrointestinal decontamination includes gastric lavage, syrup of ipecac, activated charcoal, and whole bowel irrigation. Clinical studies have delineated the role and efficacy of these procedures. Trends in GI decontamination place less emphasis on ipecac and gastric lavage and more emphasis on activated charcoal alone in the patient with a mild overdose. Gastric lavage is indicated in serious ingestion and is most effective if done soon after the exposure. Whole bowel irrigation is the newest addition and has important clinical use in the treatment of serious iron ingestions as well as in older adolescent cocaine body suffers and packers. Indications and contraindications of the various forms of GI decontamination are discussed and relevant clinical studies are reviewed.

Gastrointestinal decontamination for acute poisoning

Gastric decontamination remains an important element in the therapy of pediatric poisoning; however, several issues remain unresolved. Additional studies, particularly in the clinical setting, are necessary to establish optimal therapeutic recommendations. Based on the data presented in this review, the following general recommendations can be made for gastric decontamination in children: If it is necessary to remove an ingested toxin, ipecac syrup is the preferred method if contraindications to its use are not present. The dose should be 30 ml in children older than 1 year of age and 10 ml in children 6 to 12 months of age. Pending further studies, the use of emetics in children younger than 6 months of age cannot be generally recommended, particularly in the home setting. Gastric lavage should be considered to be of very limited use in pediatric patients. Lavage using small nasogastric tubes, except under special circumstances, is nonproductive and cannot be advocated. If it must be used, a large-bore orogastric hose should be used. Administration of activated charcoal prior to lavage should be considered. In situations in which prompt induction of emesis is not possible or contraindications to emesis exist, activated charcoal followed by, or mixed with, a cathartic (preferably sorbitol) should be used as an alternative to removal of gastric contents. Patients with significant symptoms from ingestion requiring hospitalization should receive repeat doses of charcoal and cathartic until symptoms resolve. Activated charcoal should be given in conjunction with other appropriate therapies. Although the data to substantiate this recommendation are limited, particularly in pediatric patients, it is a benign therapy that holds promise of increasing drug elimination.

Sex differences in salicylic acid metabolism in Nigerian subjects

The urinary metabolites of a single dose (1 g) of salicylic acid were investigated in black Nigerian subjects (78 females 44 males). Qualitatively, the major metabolites were the glycine and glucuronic acid conjugates. Quantitatively, there was a statistically significant difference in the level of these metabolites between female and male subjects (P less than 0.001) (using Student's t-test). The results of the present study compared with earlier published data show a statistically significant quantitative difference between black Nigerians and Caucasians (P less than 0.001). The results suggest possible racial and sex differences in the metabolism of salicylic acid.

Sex differences in the pharmacokinetics of salicylates

The kinetics of disposition of total and free salicylic acid (SA) in blood plasma was evaluated after single and multiple oral administration of acetylsalicylic acid (ASA) to healthy female and male volunteers. In both single and multiple dose studies significant sex differences were found in the plasma levels of SA, which were due, at least in part, to individual, sex-determined differences in the rate of absorption and elimination of SA; a slower absorption rate in men reduced the magnitude of the peak plasma levels of SA. The corresponding area under concentration-time curves were always significantly lower. The elimination rate of SA in men was increased in comparison with women. The higher plasma clearance in men resulted from the kinetics of absorption and elimination. The sex differences appear to be clinical significance, since men achieved lower plasma levels of SA than women after the same weight-adjusted dose of ASA.

Aspirin dosage for infants and children

The labeled dosage schedule that has long been on pediatric aspirin preparations is at variance with the recommendation in authoritative medical references, studies demonstrating antipyretic effectiveness in children, and the prescribing habits of pediatricians as revealed by a poll conducted by the authors. Aspirin pharmacokinetics are influenced by a number of physiologic factors, as well as by dosage, and complicate the problem of assuring safe and effective pediatric use. Basic pharmacokinetic considerations indicate that the increase in size of individual doses needed to assure therapeutic salicyate blood levels, thereby removing the temptation of parents to administer the drug too often, is made permissible (i.e., safe while effective) by expanding the interdose interval to four hours instead of three. A revised pediatric aspirin disage schedule is presented that better meets the practices of the pediatric community and the needs of consumers.

Dosage of salicylates for children with juvenile rheumatoid arthritis. A prospective clinical trial with three different preparations of acetylsalicylic acid

41 children with juvenile rheumatoid arthritis (JRA) and 6 with postinfectious arthropathies, aged 3--15 years, were treated with acetylsalicylic acid for 14 days during which time the patients were hospitalized. Three different acetylsalicylic acid preparations were used: a microencapsulated form, an enteric-coated form and standard acetylsalicylic acid tablets. Serum salicylate concentrations were measured by Trinder's photometric method. With doses of 90--120 mg/kg/day symptoms of salicylism appeared in about 50% of the cases. Daily doses of 2 g/m2 (not exceeding 70 mg/kg) proved relatively safe in this study, whereas symptoms and signs of intoxication appeared at doses exceeding 3 g/m2/day. In this respect there were no significant differences between the three acetylsalicylic acid preparations used. The results of this study also suggest that the serum salicylate concentrations should not exceed 2000 mumol/l (about 27 mg/100 ml). The symptoms of salicylism correlated closely with serum salicylate levels, which, in turn, correlated well with the dosage in g/m2. Elevation of serum aspartate aminotransferase was noted in 1/3 of the cases. All of these had a dose exceeding 2 g/m2, and the frequency of elevated enzyme activities increased with increasing dosage. In the group receiving enteric coated form of acetylsalicylic acid, there were fewer positive benzidine tests (12%) than in the two other groups (22--28%).

Value of monitoring plasma salicylate levels in treating juvenile rheumatoid arthritis. Observations in 42 cases

Plasma salicylate concentration was monitored in 42 children on long-term salicylate therapy for rheumatoid arthritis. A given dose of salicylate per kg resulted in large variations in plasma levels, both between individuals and for a single individual at different times. The factors responsible for such variations were studied; in 6 cases urinary metabolites of salicylate were analysed. The relation between salicylate dosage and plasma half-life accounts for the fact that small changes in dosage can result in large changes in plasma concentration. The addition of corticosteroid or ACTH therapy results in lower plasma levels of salicylate, and necessitates higher dosage of salicylate. After the introduction of routine monitoring of plasma salicylate, the incidence of toxic symptoms fell sharply.

Inhibition of salicylate and lithium absorption in the human intestine by copper sulfate

Copper sulfate, given orally in an emetic dose, decreased the absorption of therapeutic doses of acetylsalicylic acid or lithium carbonate, more than was expected judging from the recovery of salicylic acid in the vomit. Ten volunteers participated.

Salicylate poisoning complicated by fluid retention

We have presented two cases of salicylate poisoning that demonstrate fluid retention in the face of adequate hydration, resembling the syndrome of inappropriate secretion of ADH. These cases necessitated marked alterations from normal fluid therapy. Mannitol was found to be an effective, albeit transient, diuretic for treating the acute symptoms associated with fluid retention, but only strict fluid restriction resulted in a prompt and satisfactory diuresis.

Paediatric pharmacology

Infants and children differ pharmacologically from adults because the progressive maturation of various systems during development leads to variations in drug action and dosage. These differences are reviewed. Pharmacogenetic factors which affect anaesthesia and the problems of drug overdosage, as seen in paediatric intensive care units, are briefly considered.