Cognitive Function

Haward, Portsmouth Journal of Psychology (1968),585 found PHT effective in the improvement of concentration. This was demonstrated in a performance test designed to simulate air traffic control tower conditions. Twelve volunteers, nineteen to twenty-one years of age, were introduced to an air traffic control task requiring a high degree of concentration. The test was done with placebo, on a double-blind basis, and the essential variable was number of errors made. On this basis, improved efficiency was demonstrated by PHT at the significant level of p<0.01. No individual felt a drug effect of any sort. The author stated that this subtlety of action was consistent with what frequently had been observed in the clinical use of PHT. The author says that because of its high level of safety and its nonaddictive character, PHT has none of the negative qualities of the amphetamines, which have in the past been used for similar purposes.

585. Haward, L. R. C., Drugs and concentration: cognitive effect of DPH, Portsmouth J. Psychol, 1: 3-5, 1968.

Haward, Drugs and Cerebral Function (1970),1139 studied the effect of PHT upon performance in a complex task, subject to fatigue, in twelve college students who had concentration difficulties. A double-blind crossover procedure was followed. PHT was found to be significantly effective in delaying the onset of fatigue and accompanying errors.The author notes that these findings are in accord with the observations of Dreyfus 707 that poor concentration can result from forced ruminative thinking, or the “turned on mind,” and that this can be corrected by PHT. (See also Ref. 527.)

1139. Haward, L. R. C., Effects of sodium diphenylhydantoinate and pemoline upon concentration: a comparative study, Drugs and Cerebral Function, 103-120, Smith, W. L., Ed., Charles C Thomas, 1970.
 707. Dreyfus, J. J. Jr., The beneficial effects of diphenylhydantoin on the nervous systems of nonepileptics-as experienced and observed in others by a layman. Presented at the Amer. College of Neuropsychopharmacology, Dec. 7, 1966, Dreyfus Medical Foundation, 1966.

527. Haward, L. R. C., A study of physiological responses of neurotic patients to diphenylhydantoin, Int. J. Neuropsychiat., 3: S49-S56, 1967.

Goldberg and Kurland, Journal of Nervous and Mental Disease (1970),713 in a double-blind study, reported strong improvement in ability to maintain attention and concentration with PHT. (For more complete summary, see Goldberg and Kurland, In Non-Epileptics.)

Daniel, Geriatrics (1970),938 reported PHT useful for symptoms of confusion in the aged, including lack of attention and concentration. (For more complete summary, see Daniel, In Non-Epileptics.)

938. Daniel, R., Psychiatric drug use and abuse in the aged, Geriatrics, 144-156, January, 1970.

Smith and Lowrey, Drugs, Development and Cerebral Function (1972),1564 suggest that improvement in cognitive performance can be due to improved concentration. Using standard IQ tests, the authors compared PHT to placebo on twenty hospital employee volunteers. The test was done on a double-blind crossover basis. PHT, 100 mg three times daily, improved Verbal Scale and Full Scale scores at highly significant levels and the Performance Scale improvement was also significant. The authors state that their findings are consistent with those obtained by Haward.1139

1564. Smith, W. L. and Lowrey, J. B., The effects of diphenylhydantoin on cognitive functions in man, Drugs, Development, and Cerebral Function, Smith, W. L., Ed., Charles C Thomas, 344-351, 1972.
1139. Haward, L. R. C., Effects of sodium diphenylhydantoinate and pemoline upon concentration: a comparative study, Drugs and Cerebral Function, 103-120, Smith, W. L., Ed., Charles C Thomas, 1970.

Haward, Revue de Medicine Aeronautique et Spatiale (1973),1140 found that PHT significantly improved the performance of three separate groups of pilots in simulated flying and radar target-fixing tasks.Three groups of pilots, twenty-two commercial pilots, eighteen military pilots and nineteen private pilots were studied. Two absorbing tasks were required of the pilots in an attempt to reach their full channel capacity. The first was a standard flight simulation procedure. The second task consisted of monitoring and responding to a new type of radar.The pilots were scored on their ability to bring the simulated aircraft into position to correctly intercept a moving target. Sixty minutes before each task 150 mg of PHT was given. With PHT the test results showed significant improvement in performance both in terms of lessened time spent and the increased number of correct responses. In all three groups the improvement was significant. The author states that he chose PHT because other substances which have been tried for this purpose, such as amphetamine, pemoline and prolintane, can have undesirable side effects.

1140. Haward, L. R. C., Effects of DPH (sodium diphenylhydantoinate) upon concentration in pilots, Rev. Med. Aeronautique Spatiale, 12: 372-374, 1973.

Smith and Lowrey, Journal of the American Geriatrics Society (1975),1565 observed the beneficial effect of PHT upon cognitive function in a group of elderly normal subjects. In the present study ten volunteers, four male and six female, average age sixty-nine years, were studied in a double-blind crossover test with placebo control. This crossover design was used to eliminate possible practice effects on performance. With PHT significant improvement in scores occurred in information, comprehension, digit symbol and full scale IQ. The authors conclude that these significant improvements illustrate the effectiveness of PHT in improving generalized mental functions.

1565. Smith, W. L. and Lowrey, J. B., Effects of diphenylhydantoin on mental abilities in the elderly, J. Amer. Geriat. Soc., 23: 207-211, 1975.

Craig and Tallis, Epilepsia (1994), 3135 conducted a single-blind, randomized study to compare the impact of phenytoin (PHT; up to 300 mg/day) and valproate (VPA; up to 1,000 mg/day) on cognitive function of thirty-eight patients (mean age 77 years) with elderly-onset seizures. A stratified minimization program matched the two groups for age, sex, and seizure type. Attention, concentration, psychomotor speed and memory were assessed twice before treatment (to minimize practice effects), at six weeks, and, for patients remaining in the study, at three months, six months and one year by an extensive battery of psychological tests. Changes in cognitive function were minor, and some tended toward improvement. In their discussion, the authors reported that the slight adverse effects observed were more pronounced with VPA than with PHT and that more positive effects (such as decreased anxiety, decreased depression, and improved verbal memory) were noted with PHT.

3135. Craig, I. and Tallis, R., Impact of valproate and phenytoin on cognitive function in elderly patients: results of a single-blind randomized comparative study, Epilepsia, 35(2): 381-90, 1994.

See also Ref.

3136. Dodrill, C.B. and Troupin, A.S., Neuropsychological effects of carbamezepine and phenytoin: a reanalysis, Neurology, 41: 141-3, 1991.