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General principles of antiepileptic drug (AED) therapy are reviewed, current issues involving the use and monitoring of AEDs are examined, promising investigational agents are briefly reviewed, and situations that require potentially difficult decisions about long-term care are discussed. The initial treatment should be monotherapy with a first-line AED for the particular seizure disorder. The usual approach is to maximize seizure control and minimize the adverse effects of AED therapy. Current issues involving the pharmacokinetics, use, and monitoring of the conventional AEDs phenytoin, phenobarbital, primidone, carbamazepine, valproic acid, ethosuximide, benzodiazepines, and acetazolamide are discussed. AED therapy may have adverse effects on behavior and cognition. The risk of teratogenicity with well-monitored AED therapy is probably low, and severe hepatotoxicity is uncommon. Because carbamazepine, phenobarbital, phenytoin, and primidone all have enzyme induction properties, a number of clinically important interactions are possible. Issues related to discontinuing AED therapy, serum concentration monitoring, and generic interchange of AED products are addressed. Whether AEDs should be used to prevent recurrent febrile seizures, alcohol withdrawal seizures, or seizures in patients with head trauma or stroke must be considered. The treatment of seizure disorders is a complex process involving identification of the seizure disorder, selection and monitoring of an appropriate AED(s), and consideration of adverse effects and drug interactions. Whether therapy should be discontinued after a prolonged seizure-free period, compliance issues, and whether to treat certain conditions prophylactically also must be considered.

Valproic acid serum concentrations predicted by a single-dose prediction model were compared with steady-state serum concentrations measured after the start of therapy in seizure patients. Ten patients receiving valproic acid for the first time or who had not been taking the drug for two or more weeks were entered into the study. The patients' therapies were initiated with the prescribed doses of valproic acid and then maintained on fixed doses and dosing intervals until steady-state trough serum samples were obtained. Initial 5-ml blood samples were collected six to 14 hours after the ingestion of the first dose; a 5-ml steady-state trough sample was drawn in the same manner three to seven days later. Both free and total drug concentrations were determined within 48 hours of sample collection using gas-liquid chromatography. The elimination rate constant was estimated from age-specific population half-life values found in the literature. Six patients (five children, aged four to 16 years) and one adult (aged 87 years) completed the study. There was a statistically significant correlation between predicted and measured steady-state valproic acid serum concentrations for both free and total concentrations. The single-dose prediction model accurately predicted steady-state valproic acid serum concentrations in these seizure patients.

The epidemiology, pathophysiology, clinical features, diagnosis, and clinical course of rheumatoid arthritis (RA) and the role of disease-modifying antirheumatic drugs (DMARDs) in its treatment are reviewed. RA, a widespread disease affecting people of all races and sexes around the world, has an unknown and perhaps multifactorial etiology. Conflicting evidence supports an immune-complex, infectious, metabolic, or genetic basis for RA. The disease affects diarthrodial joints and begins as an immune response to unknown antigenic stimuli. A proliferative process ensues, leading to formation of a vascular lesion called a pannus, which then infiltrates into cartilage, subchrondral bone, and tendon. This destructive phase leads to classic RA symptoms of pain, limitation of motion, swelling, heat, and redness of the affected joint. Symptoms and laboratory tests form the basis for diagnosis. For most RA patients, conservative therapy provides substantial benefit. In those patients who suffer from unrelenting and progressively destructive disease, more aggressive intervention is necessary to prevent permanent disability. The DMARDs are reserved for treatment of this group of patients. DMARDs include such diverse agents as the gold compounds aurothioglucose, auranofin, and gold sodium thiomalate; the antimalarials hydroxychloroquine sulfate and chloroquine phosphate; penicillamine; and the cytotoxic agents azathioprine, methotrexate, and cyclophosphamide. DMARDs are effective but toxic therapeutic agents. Because of the toxicities of these agents, careful monitoring at regular intervals is necessary throughout the duration of therapy. For patients in whom these drugs demonstrate efficacy and are tolerated, the DMARDs may attenuate the disabling effects of long-term erosive disease.

The effects of errors in gentamicin concentrations were assessed using computer simulation. Steady-state concentrations at the end of a one-hour infusion (Cmax) and at the end of the dosing interval (Cmin) were calculated for four simulated patients with three dosing schemes each. Errors from -80% to +80% were systematically induced in Cmax or Cmin, or both. Pharmacokinetic values were calculated from the error concentrations and then used to determine new dosing regimens given specific desired concentrations. True Cmax and Cmin values were calculated using the new dosing regimens and original pharmacokinetic values. As the absolute value of the induced error increased, increases were generally seen in the absolute value of the resultant error and in the deviation of the true Cmax and Cmin from desired values. Resultant error was more evident with induced error less than zero, when error was induced into Cmax, and with shorter dosing intervals. Resultant error in pharmacokinetic variables was greater than induced error at induced errors as low as +/- 5%. Toxic and suboptimal values for the true Cmax and Cmin rarely occurred with induced errors of -20% to +20%. Errors in serum gentamicin concentration measurements are more likely to cause larger resultant errors as the errors in concentration values (1) increase in magnitude, (2) result in underreporting of the concentration values, or (3) affect peak concentration values. Shorter dosing intervals may also increase the influence of assay errors.