Br. J. clin. Pharmac. (1978), 6,493-497
COMPARISON OFTHE EFFECT OF DRUGS UPON SOME COMMONLY USED MEASURES OF BOWELTRANSITTIME H.J. ROGERS, F.R. HOUSE, P.J. MORRISON & 1I.D. BRADBROOK Departments of Clinical Pharmacology and Pharmacology and I Department of Forensic Medicine, Guy's Hospital Medical School, London SE1 9RT
I To study the effect of drugs on methods of assessment of gut transit time a double-blind study of the effect of single doses of placebo, oxyphenisatin, anthracene purgatives, (+)-norpseudoephedrine and a combined preparation of (+)-norpseudoephedrine and senna was carried out in ten normal volunteers. Gut transit time was assessed by dye and radio-opaque marker methods. 2 It was possible to demonstrate the effect of the anthracenes but not oxyphenisatin on gut transit time. 3 More sophisticated statistical techniques were required to demonstrate the retarding effect of the sympathomimetic amine and its reversal by senna. 4 Statistical analysis shows that assessment of intestinal transit time by dye or pellet methods gives identical information.
Introduction A number of recent publications have recorded alterations in bowel transit time and stool weight produced by dietary modification (Payler, Pomare, Heaton & Harvey, 1965; Durrington, Manning, Bolton & Hartog, 1976) or environment (Glober, Nomura, Kamiyama, Shimada & Abba, 1977). The most usual method employed in assessing bowel transit time has been the radio-opaque marker technique described by Hinton, Lennard-Jones & Young (1969). We have investigated the effects of a number of drugs on several measures of bowel transit time. Little has been published regarding the effects of drugs on intestinal transit time since the report by Hinton (1967). We have found that statistical discrimination of effects on bowel transit time, which are often subjectively obvious, may be difficult.
Methods Two experiments were carried out employing eight healthy adult males (ages from 21-39 years, mean 29 years and weighing from 52-75 kg, mean 67.5 kg) and two healthy females (aged 33 and 36 years, weights 54 and 60 kg respectively). None of the volunteers were taking any mdication at the time of the study and all had a normal and regular bowel habit falling within the limits defined for a normal population (Connell, Hilton, Irvine, Lennard-Jones & Misiewicz, 1965). Subjects maintained their normal dietary habits throughout and continued their normal duties. After giving informed consent, the subjects were randomized into three groups to receive, in a
double-blind fashion, two tablets of either placebo, oxyphenisatin (8 mg/tablet) or tablets containing a mixture of anthracenes (Aloes 65 mg; Cascara 30 mg, F,rangula 15 mg and Turpeth 5 mg in each tablet). Treatment periods were separated by intervals of 1 week. At the beginning of each experimental week, the subjects took the following with the allocated treatment and a light evening meal: a) 3 capsules each containing 500 mg carmine (Mulinos, 1935). The capsules were no. 1 size gelatine and and preliminary in vitro disintegration tests carried out according to the British Pharmacopoeia standards gave a mean disintegration time of 10 minutes. b) Twenty radio-opaque barium sulphate impregnated pellets, specific gravity 1.25, approximately cubeshaped with a mean weight of 30 mg (Portex Ltd, Hythe, Kent). When given in this manner, the marker pellets are representative of the transit time of the food residues from that meal (Hinton et al., 1969). After dosing, all faeces passed were collected (Hinton et al., 1969) and the time of defaecation noted. The faecal specimens were weighed and examined by two observers for the presence of carmine dye. The number of radio-opaque pellets in each sample was determined by fluoroscopy using a Phillips Image Intensification System. These collections were continued until all the markers (both dye and pellets) had been cleared. Volunteers were asked for their subjective impression of each treatment. Following a period of several weeks, a second study was undertaken utilising the same design and
H.J. ROGERS, F.R. HOUSE, P.J. MORRISON & I.D. BRADBROOK
measurements of gut transit time. The alternative treatments were single matching tablets of placebo, (+)-norpseudoephedrine (30 mg in a slow release preparation) or (+)-norpseudoephedrine and senna (30 mg of the sympathomimetic amine in a slow release form, plus 60 mg senna).
Results The effects of the various treatments on measures of
gastrointestinal transit are shown in Table 1.
The times to first bowel action, first appearance of dye, first appearance of pellets, 80% pellets, 100% pellets and all dye gone were submitted separately to the standard univariate analysis of variance for a randomized block design. In this preliminary analysis, no examination for non-additivity was performed. A plot of residuals against their expected normal order statistics revealed no evidence of gross outliers or of non-normality of any of the variates. The results of this analysis are summarized in Table 2. In the first experiment with laxative compounds the treatment F ratio was significant at the 5% level for two measurements only: time to first appearance of dye and the time to clear all of the dye from the faeces. For these variates the means were compared by Duncan's multiple range test (Duncan, 1955). At P=0.05, the differences between oxyphenisatin and placebo were not significant for either variate but the difference between placebo and the anthracene purgatives attained significance. The frequency of bowel opening to clear all the pellets and all the dye was compared for these three treatments by the non-parametric Friedman rank analysis of variance (Siegel, 1956). The respective test statistics for treatment differences were 9.5 and 8, critical value 62, which was not significant at P=0.05. In the second experiment with the sympathomimetic amine, whilst examination of the means reveals a situation in accord with the effects to be expected from a knowledge of the pharmacology of the drugs used, the analysis of variance demonstrates that the treatment effect is not statistically significant for any of the measured variates. Since analysis of one variate at a time failed to demonstrate a significant difference, although the difference between treatments was subjectively obvious to the volunteers, a multivariate approach was adopted. An initial multivariate analysis of variance indicated that overall differences between treatments were significant. A linear function of the observed variates was sought which would maximize the overall F-ratio for treatments in the analysis of variance (Harris, 1975). The linear function adopted was Z =-125.6y, + 132.9y2 + 50.35y3 + 10.7 1y4 + 69.44y5 -8 1.62y6 - 524.0y7 + 346.5ys + 9.23y9 + 0. lOylo where y1 is time to first bowel opening Y2 is time to first appearance of dye
y3 is time to first appearance of pellets y4 is time to clear 80% pellets y5 is time to clear 100% pellets Y6 is time to clear all dye y7 is number of bowel openings to clear 100% pellets y8 is number of bowel openings to clear all dye yg is weight of faeces to clear 100% pellets ylo is weight of faeces to clear all dye The analysis of variance for Z appears in Table 3, which also gives the treatment means expressed in arbitrary units. The differences of treatments relative to placebo with confidence limits calculated at the P= 0.05 level were that the increase in transit time due to (+)-norpseudoephedrine was 1397 units with limits of 643 to 2151 units which was significant (P=0.0007) and the decreased transit time associated with the addition of senna to the sympathomimetic amine was 834 units with limits of 80 to 1588 which was also significant (P=0.028). These tests and limits allow for the post-hoc nature of the selection of linear function and the multiple comparisons involved. It may therefore be concluded that it was possible to demonstrate the retarding effect of (+)-norpseudoephedrine on gastrointestinal transit and the reversal of this effect by senna. For each experiment an additional analysis of variance was computed for the time to first appearance and time to disappearance of the dye and pellets. The important term in these analyses was the two-way interaction between drug and the markers used to characterise intestinal transit time which indicates the extent to which the drug effect varies with the marker used. In no case did this interaction reach statistical significance at the 0.1 level and it is therefore concluded that there is no evidence that these two marker methods give differing information. In these analyses in every case the drug effect upon the markers was statistically significant at the 0.05 level indicating that the markers are sensitive to drug effects. During these experiments the recovery of the markers was 100% and there were no adverse effects from either the drugs administered or the measurement of their effects.
Discussion A wide range of methods for the measurement of
gastro-intestinal transit time have been proposed. Early radiological methods such as those pioneered by Hurst (1919) at this hospital required the use of radioopaque substances such as barium sulphate which may in themselves alter the transit time (Alvarez & Freedlander, 1924). Coloured powders such as carmine require careful examination of the stool to
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H.J. ROGERS, F.R. HOUSE, P.J. MORRISON & I.D. BRADBROOK
determine the first and last appearance of the dye. Various types of pellets have also been employed to measure transit time. Coloured glass beads were used by Alvarez & Freedlander (1924) in their classical work on gastro-intestinal motility, but this method requires that the stools be sieved to detect the presence of the markers. Furthermore, glass beads have a relatively high specific gravity by comparison with food residues and may not give a representative value for transit time (Hoelzel, 1930). The use of radioopaque pellets which have the same density as food residues within the bowel which do not apparently alter gut motility and which merely require that the stools be X-rayed, therefore represents an advance on these older methods. Hinton et al. (1969) compared the transit time of pellets and of a simultaneously administered dose of '1Cr-labelled sodium chromate and found that although the times for the first appearance of the markers were similar, the times for the later pellets were less than the times for the corresponding portions of chromate in the majority of their subjects, possibly due to a delay in the upper gut. A comparison of the transit time of pellets and dye was made but no statistical analysis performed. The data presented in this paper suggests that both types of marker satisfactorily indicate gut transit time and are responsive to changes produced by drug treatment. However, as we have here reported, in studies employing small numbers of subjects, the changes produced by single doses of drugs affecting Table 2
intestinal motility often require sophisticated statistical analysis to demonstrate drug effects. It may be of some interest to consider the sample size needed to produce a significant result in the experiment with (+)norpseudoephedrine where the treatment effect was not significant for any of the measured variates taken one at a time in an analysis of variance. The most sensitive measurement in that experiment was the weight of faeces to clear all the pellets. As an illustration, if that were true for a larger sample, and if the difference in means and variability were to remain the same, then a sample size of 15 would just suffice to produce a statistically significant effect with a probability of 0.75 at a significance level of 0.05 (i.e. there would be a 75% chance of detecting a significant difference). In the experiment comparing laxatives, the measurements of transit time by dye passage appear to be slightly more sensitive to drug effects than pellet methods, perhaps reflecting the greater fluid content of the faeces (as suggested by the trend towards an increased faecal weight to clear dye and pellets) which would tend to promote the transit of dye relative to pellets. Our data suggests, however, that both types of marker are responsive to changes in gut transit time produced by drug treatment. The multiple marker method recently described by Cummings, Jenkins & Wiggins (1976) may perhaps give further information. The data presented for intestinal transit time in normal subjects shows that most subjects cleared the markers over a range of 2 to 5 days. These times
Summary of univariate analysis of variance for measures of bowel transit time following treatment with placebo, oxyphenisatin or anthracene purgatives
Duncan test at P=0.05
P for treatment F
(underlined pairs not significantly different) Time to first bowel opening Time to first appearance of dye Time to first appearance of pellets Time to clear 80% pellets Time to clear 1 00% pellets Time to clear all dye Weight to clear 100% pellets Weight to clear all dye Table 3
0.32 0.078 0.22 0.14 0.5 0.036 0.17 0.15
Analysis of variance of Z (see text)
Subjects Treatments Residual
Sum of squares
Degrees of freedom
2.3022 x 1 08 2.5411 x 1 O' 8.1497 x 10.
9 2 18
2.558 x 107 1.270 x 107 4.528 x 1 0'
Treatment means were placebo 11 1201 units
(+)-norpseudoephedrine 2598 units (+)-norpseudoephedrine + senna 367 units
BOWEL TRANSIT TIME
are consistent with the review of the literature data by Cummings et al., (1976). Little has been published on the effect of purgatives on intestinal transit time. Hinton (1967) demonstrated the effects of senna and magnesium sulphate based upon only two constipated patients and utilizing only opaque pellets. More recent studies upon the effects of pectin (Durrington et al., 1976) have demonstrated no change in whole gut transit time. Similar investigations into the effects of bran have either failed to detect a change (Eastwood, Kirkpatrick, Mitchell, Bone & Hamilton, 1973) or suggest a regression towards the mean transit time when bran is added to the diet (Payler, et al., 1975).
These investigators confined their statistical analyses to simple paired t-tests and possibly a more detailed analysis would reveal undetected effects of these treatments. This present study demonstrates that with small numbers of subjects it is possible to detect with some difficulty the effect of an anthracene laxative mixture on gut transit time although subjectively this distinction between this treatment and placebo was obvious to all subjects. It also supports the view that there is little clinical evidence of the efficacy of oxyphenisatin (Godding, 1973) which has, in addition, been implicated in the causation of chronic active hepatitis.
HARTOG, M. (1976). Effect of pectin on serum lipids and lipoproteins, whole gut transit time and stool weight. Lancet, H, 394-396.
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