Serum concentrations of valproic acid: influence of dose and comedication

The influence of valproate (VPA) dose, VPA preparation used, comedication (phenobarbital, phenytoin, carbamazepine) and factors such as age, weight, height, and sex on the concentration of VPA in serum was investigated. Nonlinear regression analysis showed that about 63% of the variance in the VPA morning concentrations of 259 inpatients could be explained by the following variables: dose, body weight, sex, and comedication. Age, height, and kind of preparation had no important influence on the VPA concentration. The relationship between dose and concentration of VPA is nonlinear, as the concentration does not increase proportionally with the dose but increases to a lesser extent. The serum concentration of VPA is clearly lower when the drug is given in combination with phenytoin (49.5%), carbamazepine (66.2%), or phenobarbital (76.3%) than when given alone (100%).

Systematic comparison of three basic methods of sample pretreatment for high-performance liquid chromatographic analysis of antiepileptic drugs using gas chromatography as a reference method

Sera of epileptic patients which were routinely examined by gas chromatography (GC) were also analysed using high-performance liquid chromatography (HPLC). Three basic methods for the pretreatment of samples for HPLC analysis were compared: protein precipitation by adding acetonitrile to the serum, direct serum extraction using ethylacetate, and partitioning of serum and buffer solution over a stationary phase and extraction with dichloromethane/2-propanol. The analytical performance and practicability of the three methods were tested under routine conditions. The following anti-epileptic drugs and metabolites were used in the comparison of HPLC with GC: ethosuximide, primidone, phenobarbital, phenytoin, carbamazepine, N-desmethylmethsuximide, and phenylethylmalonediamide.

Urinary hydroxyphenytoin/creatinine ratios as an index of compliance in adult epileptic patients on phenytoin therapy

The ratio of the concentration of the phenytoin metabolite hydroxyphenyl phenylhydantoin (HPPH) to the creatinine concentration in morning urine samples was used as an index of compliance in adult epileptic patients on phenytoin therapy. For this purpose, the phenytoin dose was estimated from the urinary HPPH/creatinine ratio with the help of a regression equation that took into consideration body weight, height, age, and sex. A high correlation (r = 0.927 for men and r = 0.954 for women) between the prescribed and estimated dose was found for a reference group (127 hospitalized patients on supervised drug regimen). Compliance was judged from the discrepancy between the prescribed and the estimated dose for 45 patients immediately after their admittance to an epilepsy clinic, as well as for 98 outpatients, who had been treated by neurologists. Noncompliance was suspected in 6.7% of patients admitted to the clinic, as well as in 28.6% of the outpatients.

Effect of a rocking bed on apnoea of prematurity

We describe a rocking bed for use in incubators. Its effect was studied in 12 preterm infants with idiopathic apnoea, using each as his own control. All but one had less apnoea when the bed was rocking than when it was still. Apnoea associated with a significant fall in transcutaneous PO2 was less frequent, and fewer interventions were needed to terminate apnoeic attacks.

Are potassium supplements for the elderly necessary?

Plasma and total-body potassium (TBK) were measured in 19 elderly patients receiving diuretics and potassium supplements for cardiac failure and in 13 elderly controls. The mean value for the ratio of TBK to fat-free mass (TBK:FFM) was significantly reduced in the patient group. TBK:FFM showed a negative correlation with age but no correlation with plasma potassium or dose of supplements. When controls and patients were matched for sex and age decade, the mean TBK:FFM was decreased significantly in the diuretic group, giving a mean potassium deficit of 13.3%. These results suggest that ageing influences potassium status, and that diuretics and cardiac failure have a greater effect on TBK in old age than in youth or middle age.

The effect of potassium supplements on total-body-potassium levels in the elderly

Weight, skinfold thickness, grip strength and the total-body-potassium content were measured in 13 healthy elderly subjects before and after a three-month course of potassium supplements given in a dose of 36 mmol per day. There were no significant changes in the total-body-potassium content or in the ratio of total body potassium to lean-body mass. An increase in the right-hand grip strength may well have been a placebo effect.

Whole-body and exchangeable potassium measurements in normal elderly subjects

A comparison of total body potassium status of eighteen healthy subjects with normal renal function in the age group 65-85 years, measured by whole body counting and by total exchangeable potassium on plasma and urine samples taken at 24h, shows that there is no delay in exchange in radioactive potassium in the elderly, and that the exchangeable method gives a reliable value of total body potassium. The results suggest that the normal range for potassium per kilogramme body weight is lower for old persons than for younger age groups.