sulphate and magnesium citrate)' or Golytely (a balanced electrolyte solution containing poly- ethylene glycol)'-are required for bowel pre- paration before ...
in immunocompromised patients (S E Young, personal communication). Not onlyedoes DF-2 infection have similar transmission and clinical expression to P multocida infection but the organism is also sensitive to penicillin. I wonder whether yet other domestic zoonoses will come to light, initially in more susceptible and investigated subjects, and later in non-immunocompromised subjects, who might anvway be treated blindly with penicillin or even recover spontaneously; such an illness could easily be attributed to a "virus." W P A WHITEHOUSE
Hopc Hospital. SaltfOrd, Manchester M6 8Ht)
Mc(arth\ M.\i,ZumiaA. 1)1 -2 inictcion. BrJ1cd7 19 8;297:1955. 26 November. 2 Itoh M,.1 lierino P1M, Milstoc *\1, ci al. A uinique ouibrcak of PastUrclla multocida in a chronitc discasc hospital. -An Publici 1lcalth i980;70:117i0-3. 3 Rafthi F1 Barrier J, Baron 1), ct a1l. I'astcurclla multocida battcracrnia: report ot tlhirtceel cascs over twelve years and review ol thc litcrature. Scand7 Inft'ti Dis 1987;19:385-93.
A policy for laxatives SIR,-I wish to comment on two aspects of the editorial by Drs D N Bateman and J M Smith' that are misleading to prescribing clinicians and may therefore adversely affect patient care. Drs Bateman and Smith state that in higher doses lactulose max cause electrolyte imbalance, but the editorial is concerned with the treatment of constipation and the reference given' relates to the use of lactulose to treat acute portal systemic encephalopathy. In fact, the paper reports a single case of an unconscious patient with acute portal systemic encephalopathv who was treated with 3 litres lactulose in four days (daily dosage 720 ml) and developed hvpernatraemia. This dosage is more than 20 times the normal starting dosage of lactulose to treat constipation in adults. The authors' conclusion draws attention to the risk of hvpernatraemia with such high dosages of lactulose in patients who do not have free access to water. The use of this reference when discussing the treatment of constipation is inappropriate. Drs Bateman and Smith also stated that tolerance may develop with prolonged use, but the reference cited' is a paper reporting a small study in eight health,, volunteers that was carried out over eight davs and was designed to evaluate the effect of lactulose ingestion on lactulose metabolism within the colon. TFhe paper reports changes in colonic bacterial metabolic pathways during lactulose treatment that would not result in any reduction in the efficacy of lactulose as a treatment for constipation, and the authors make no mention of tolerance. Trhis study, in volunteers over just eight days, does not support the statement that tolerance to lactulose in the treatment of constipation occurs with prolonged use and we are not aware of any studv that does. A M WHITEHEAD ,Medicil I)Dcpartincnt, Duiiphar La.tbotrarorics Linlitcd.
SOLIOMM.A0111 S03- 3J D
Smit1h JM. A policy ;297:14210-l. 3 D)cccmhcr.
13,amitan D)N, 198 2
for laxatives. Br
Medj 7
NaiX1'j AA, lattcncr RW. ILtctttlosc-induccd hvpcrnatremia. I)ru,t lIntIll C/nit /laritt 1984;18:7(- 1. lFtturic B, Raitntrcatt MB, Bcrnier JJ, Rambattd J. InlltLtc1CC ol chronic lictLulose inigcstioni onl the coloiic lctabolismn ot lactulosc in man. 7 C/t Invto 1985;75:60(-13.
3 Florcnt C,
AUTHORS' RE'LY, - Dr A M Whitehead suggests that two of the comments in our editorial are misleading and may therefore adversely affect patient care. We strongly refute both these suggestions. In general the pharmacology of and
188
adverse reactions to laxatives are inadequately documented. From the limited published data it is nevertheless clear that lactulose may be associated with electrolyte disturbances and that with prolonged treatment changes in colonic metabolism occur that are likely to result in tolerance. Reported cases of electrolyte disturbance have generally been in patients receiving lactulose for hepatic encephalopathy, but this may occur at moderate doses. In a series of 75 courses of treatment 20 were associated with hypernatraemia (sodium > 145 nmol/l). Two of these patients were receiving 40 ml a day, only a little higher than the recommended dose for treatment of constipation, while another two were receiving 60 ml a day.' Concern about this potential adverse effect has led the American College of Gastroenterology to state (in a review of the treatment of constipation) that lactulose may cause electrolyte disturbances,' and the American Medical Association advises that serum electrolyte values should be measured periodically in elderly debilitated patients who receive lactulose for more than six months.' Our statement that tolerance may occur was based on a well designed studv of colonic lactulose metabolism in eight subjects.4 After eight days' treatment with 20 g twice daily caecal concentrations of lactulose, fructose, and galactose after a dose were significantly lower than on day 1. Conversely, concentrations of lactic acid, acetic acid, and total volatile fatty acids were significantly higher and the pH of caecal fluid fell more rapidly and to a lower value than on day 1. These findings strongly suggest that bacterial catabolism of lactulose and its constituent hexoses is increased after prolonged use. As the resulting short chain organic acids are at least partially absorbed in the colon it follows therefore that the colonic osmotic load will be reduced and laxative efficacy may be diminished. We are not the first authors to interpret this study as indicating that tolerance may occur. As a result of these observations, other adverse effects such as flatulence and abdominal cramps, and the comparatively high cost of lactulose we endorse the view expressed elsewhere-' ' that this agent should be reserved for patients who do not respond to other laxatives. D N BATEMAN J M SMITH
WXolfson Unit ol-C linical Pharmacology, University of Newcastle utporn Tyne, Newcastle upon lTne NEI 7RU I Nelson
I)C, McGrew WRG, Hoyumpa AM. Hypernatremia and
lactulose therapy 2 'I'cdesco
J7AMA 1983;249:1295-8.
lJ. Laxative
1985;80:31)3-9.
use in constipation. Am J (Gastroenterol
3 Amcrican Medical Association. D)rug evaluations. 6th ed.
I'hiladelphia: Satinders, 1986:975-87. 4 Florent C( Flouric B, Rautureau M, Bcrnier JJ, Rambanid J. Influcnce of chronic lactulose ingestion on the colonic metabolism otf lacttilose in man.,7 Clin Invest 1985;75:608-13. 5 Anonymous. Laxatives: replacing danthron. I)rug 7her Bull
1988;26:53-6.
SIR,-I welcome the editorial by Drs D N Bateman and J M Smith' as it urges us all to review our management of constipation, especially as this is a problem in which the management decisions should primarily be medical rather than nursing. The authors clearly recognise that constipation is a major problem in the elderly. About half of the patients admitted to geriatric units are constipated.2 I was surprised, however, that they attribute constipation in the elderly to poor diet and poor abdominal and perineal muscle tone without mentioning immobility, which is a much more important factor in these patients.' Faecal impaction complicates constipation in many geriatric patients. About half of these impacted (loaded) patients have massive amounts of soft faeces in their rectum. Using any agent that causes faecal softening-for example, lactulose,
bulk forming laxative, or fibre-will tend to increase their risk of becoming faecally incontinent as soft stool leaks more readily than hard stool. Taking account of stool consistency is therefore important before prescribing a laxative preparation. Most constipated geriatric patients suffer from slow transit constipation,4 and stimulant laxatives -for example, senna-are widely used in their management. In elderly patients these laxatives tend to exert their effect in the colon 10-14 hours after oral administration. It is thus important that they are given at bedtime to reduce the risk of nocturnal faecal incontinence.' The authors suggest that prolonged use of stimulant laxatives may cause an atonic colon. Although this may be true, the evidence to support this is limited and inconclusive. Myenteric plexus damage induced by laxatives, which has been shown in mice,6 has been suggested as the probable mechanism. Myenteric plexus degeneration has also been shown in colectomy specimens from chronically constipated patients. Possibly, however, the myenteric plexus abnormality in these patients is the cause of their constipation rather than the effect of its treatment. Finally, the laxative agents cited by the authors are unlikely to deal adequately with all the indications listed. More potent preparationsfor example, Picolax (a mixture of sodium picosulphate and magnesium citrate)' or Golytely (a balanced electrolyte solution containing polyethylene glycol)'-are required for bowel preparation before operations or diagnostic procedures or for treating patients with constipation that is resistant to milder preparations. JBARRETT D)epartment of Geriatric Medicine,
Hope Hospital. Manchester M6 8HD I Bateman DN, Smith JM. A policy for laxatives. Br Med J 1988;297:1420-1. (3 December.) 2 Read NW', Abouzekrv L, Read MG, Ottewell D, Donnelly TC. Anorectal function in elderly patients with fecal impaction.
Gasroenterology 1985;89:959-66. 3 l)onald IP, Smith RG, Cruilkshank JG, Elton RA, Stoddart ME. A study of constipation in the elderly living at home. Gtrontology 1985;31:112-8. 4 Brocklehurst JC, Kirkland JL, Martin J, Ashford J. Constipation in long-stay elderly patients: its treatment and prevention by lactulose, poloxalkol-dihydroxyanthraquinolone and phosphate enemas. Gerontology 1983;29:181-4. 5 Harvard LRC, Hughes-Roberts HE. The treatment of constipation in mental hospitals. Gut 1962;3:85-90. 6 Smith B. Effect of irritant purgatives on the myenteric plexus in man and the mouse. Gut 1968;9:139-43. 7 Krishnamurphy S, Schniffer MD, Rohrmann CA, Ope CE. Severe idiopathic constipation is associated with a distinctive abnormality of the colonic myenteric plexus. Gastroenterology 1985;88:26-34. 8 Foord KD, Morcos SK, Ward P. A comparison of mannitol and magnesium citrate preparations for double-contrast barium enema. Clin Radiol 1983;34:309-12. 9 l)avis GR, Santa Ana CA, Morawski SG, Fordtran JS. Development of a lavage solution associated with minimal water and electrolyte absorption or secretion. Gastroenterology 1980;78: 991-5. 10 Puxty JAH, Fox RA. Golytelv: a new approach to faecal impaction in old age. Age Ageing 1986;15:182-4.
Real progress with disciplining doctors SIR,-The leader by Dr Malcolm Forsythe on the recent proposals for disciplining doctors belies the fact that the joint working party report is deeply flawed (and innumerate). The report claims that there were only 15 inquiries in the past 10 years. In fact, there are over 60 cases of suspended doctors extant, and no data on this subject are collected centrally. The working party proposals may well suit the administrators but do little for doctors. Although time limits are proposed for the various stages in the suspension process, nothing is suggested if these are exceeded. As it is not unknown for a health authority to ignore an instruction from a High Court judge to get a move
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JANUARY
1989
