BLUE NAPPIES

499 incidence of y in Nagasaki found in the statistical analyses will be carried out. Department

of

study, further

Bacteriology,

Tohoku University School of

Medicine,

Sendai, Japan.

NAKAO ISHIDA TAKUSEI UMENAI.

Institute for Cancer

Research, Philadelphia, Pennsylvania 19111, U.S.A. Fox Chase,

ANNA O’CONNELL IRVING MILLMAN.

BIOAVAILABILITY OF DIGOXIN

SIR,-Since the bioavailability of digoxin has been extensively investigated and discussed, we feel that the full reference list is unnecessary. The index of bioavailability has been the peak plasma-level or the area below the plasma-level/time curve. Because of the low sensitivity of the radioimmunoassay (R.I.A.), plasma-levels are usually recorded for only 5 or 6 hours after administration, although occasionally this has been extended to 12 hours or more. From kinetic data obtained using labelled digoxin we know that the area under the plasma-level/time curve up to 6 hours represents about 20% of the area extrapolated to infinity, so it should follow that differences in the areas under the plasma curves up to 5 hours cannot be extrapolated to predict the amount of digoxin which will eventually be absorbed. Surprisingly, however, Wagner et al.1 have found that the bioavailability of two tablet preparations, as judged by their 5-hour and 4-day total areas under the plasma curves, maintained the same proportional relationship. A more accurate estimate of the amount of digoxin eventually absorbed can be obtained from the cumulative urinary excretion of digoxin over a sufficiently long period of time.2 We report preliminary results of a study in which we estimated plasma concentration and cumulative urinary excretion of digoxin in six healthy volunteers using a radioimmunoassay method (’Digok-Kit’). Each volunteer received in a randomised sequence two 0-25 mg. tablets (Sandoz digoxin) and one 0-5 mg. capsule containing coarseparticle digoxin, with at least 2 weeks between doses. The capsules were specially prepared for this investigation since it was anticipated that they would have a poor bioavailability. Plasma was sampled up to 6 hours and urine was collected for 144 hours. The mean plasma-digoxin levels obtained are shown in the figure. For both cases the peak level was at 1 hours, but the area under the capsule curve was only 46% of that Wagner, J. G., Christensen, M., Sakmar, E., Blair, D., Yates, J. D., Willis, P. W., Sedman, A. J., Stoll, R. G. J. Am. med. Ass. 1973, 224, 199. 2. Huffmann, D. H., Azarnoff, D. L. ibid. 1972, 222, 957.

under the tablet curve. Also, less digoxin was excreted up to 144 hours after capsule administration, but if related to the amount excreted after tablets this difference was only 22%. Therefore statements on bioavailability based on areas under plasma curves up to 6 hours may differ from those based on cumulative urinary excretion data (by a factor of two in our study) and would suggest that the bioavailability is much worse than it is. We recommend that cumulative urinary excretion data over a sufficiently long period be used to estimate bioavailability of a substance such as digoxin. Experimental Therapeutics and Biopharmaceutical Departments, Sandoz Ltd., CH-4002 Basle, Switzerland.

T. R. F. E.

BEVERIDGE SCHMIDT KALBERER

NÜESCH.

BLUE NAPPIES

SIR,-The presence of an abnormal colour on

an infant’s which poses an interesting diagnostic problem. We should like to report an infant whose nappies and bibs had a blue-green colour which we believe was due to the production of unusually large amounts of pigment from a strain of Pseudomonas aruginosa. The discoloration of the overnight nappies was first noticed at 3 weeks of age and continued for about 4 months. The who was otherwise normal, was being fed on a cow’s milk preparation. Laboratory investigations which included serum calcium and phosphate, urinary aminoacids, and faecal tryptophan were all normal. A urine culture at the time the baby presented yielded a growth of skin contaminants including Pseudomonas aeruginosa, 103 organisms per ml. The baby continued to thrive, and at 3! months of age the baby’s bibs were also discoloured where they had been in contact with the saliva, and Pseudomonas ceruginosa was isolated from a throat swab. The sam e organism was isolated from the fasces. On questioning the mother it was found that it was her practice to rinse the nappies in water and place them in a bucket; there was no attempt at disinfection. With the addition of hypochlorite to the bucket the blue-green colour no longer occurred. The strain of Pseudomonas aruginosa was compared with other laboratory isolates and found to be an extremely strong pigment producer. Although stool and urine pigmentation due to bacterial growth of Serratia marcescens is well recognised,l there have been only 2 reported cases of blue nappies caused by Pseudomonas aeruginosa,2.3 and to our knowledge this has not been reported in this country. Whenever a blue discoloration of a nappy is reported the investigations should include bacteriological examin-

nappy is

a

dramatic

event

baby,

1.

Plasma-digoxin/time

curves

1. 2. 3.

Cone, T. E. Pediatrics, 1968, 41, 654. Libit, J. A., Ulstrom, R. A., Doeden, M. S. J. Pediat. 1972, 81, 546. Buist, N. R., et al. ibid. p. 622.

after 0’5 mg. digoxin in tablet

or

coarse-particle capsule form.

500 ation of faeces and urine and questioning the mother way she disinfects the nappies. Southmead Hospital, Bristol BS10 5NB.

on

the

M. J. THEARLE* R. WISE J. T. ALLEN.

DEFICIENCY OF VITAMIN E AND MYOCARDIAL INFARCTION

SIR,-In Professor Anderson’s interesting hypothesis p. 298) much that is correct is not original and

(Aug. 11,

much that is original is wrong. He repeats the well-known facts that food processing decreases biologically effective antioxidants (of which the most important are tocopherols or vitamin E) and that a main function of these is to protect polyunsaturated fatty acids in the diet and in the body, thereby preventing the formation of lipid peroxides. But he then attributes the rise in deaths from myocardial infarction that started in certain countries around 1920 mainly to the widespread adoption of oxidative processing of bread flour, mentioning the use of chlorine and nitrogen trichloride; and he is at a loss to explain why males should be much more severely affected than females. In your columns seventeen years ago1I attributed atherosclerosis and coronary thrombosis to a chronic relative deficiency of essential fatty acids (E.F.A.). In the context of human diets and body composition E.F.A. are the fatty acids of the linoleic (C18:2co6) and linolenic (C18:3to3) classes; linoleic can be converted in the body to arachidonic (C20:4o)6), and linolenic to the long-chain highly unsaturated fatty acids found in marine oils (such as docosahexaenoic, C22:6(o3). (The shorthand nomenclature is standard: C18 implies that the fatty acid has eighteen carbon atoms; the figure after the colon is the number of double bonds in the chain, all of which have the cis configuration; the figure after the omega is the position of the first double bond counting from the methyl end, and all of the double bonds are separated by methylene groups.) In an early paper2included linolenic acid in the class of B.F.A. despite the fact that it does not cure the skin lesions of rats deficient in E.F.A. though it does, however, permit growth ; and in certain persons (for instance vegans) it must be the source of the docosahexaenoic acid that is always found as a constituent of myelin and is almost certainly a required constituent for proper function. I further called attentionto the possible relation of vitamin Bg, which was then thought to be essential for the conversion of linoleic to arachidonic acid, and of the removal of vitamin E by lowering the extraction-rate of flour and destroying the remaining portion by flour improvers: " This disastrous change arises partly from processes of manufacture such as the hardening of fats, and partly from the use of low-extraction flourimproved’ with oxidising agents. Since the requirement of males for E.F.A. is much greater than that of females, the consequences are In lower animals the requirement more serious in males." of E.F.A. for males is 5-10 times that of females during the period of reproductive activity. It is perhaps of interest that E.F.A. of either class are the precursors in the body of prostaglandins,3 and men excrete in the urine about five times more of the metabolic products of these,4 but this represents only a very small proportion of the E.F.A. in the diet. In subsequent communications I was careful to point out that the highly unsaturated fatty acids of the linolenic *

Present address: Mater Children’s Hospital, Brisbane, Australia. 1. Sinclair, H. M. Lancet, 1956, i, 381. 2. Sinclair, H. M. Biochem. Soc. Symp. 1952, 9, 80. 3. Van Dorp, D. A. Ann. N.Y. Acad. Sci. 1971, 180, 181. 4. Samuelsson, B., Granström, E., Gréen, K., Hamberg, M. ibid.

p. 138.

class (such as those in cod-liver oil) were extremely toxic in presence of oxygen and absence of vitamin E because of the great toxicity in the body of lipid peroxides; and I argued 5,6 for the retention of high-extraction flour and pointed out the possible disadvantages of treating flour with oxidising agents such as chlorine dioxide (which is now used to treat about 80% of the flour used in this country, but is not mentioned by Professor Anderson). But I was careful to point out5 that myocardial infarction was very common in certain countries such as New Zealand where flour improvers were not used, and " further research is required to determine what part, if any, is played in the xtiology of human disease by the destruction of tocopherols ". We are at present engaged on such research. I believe Professor Anderson is wrong in attributing the rise in myocardial infarction mainly to an antioxidant deficit arising from the oxidative processing of bread flour. For instance, the figures he quotes for deaths in males aged 45-64 increased between 1947 and 1967 more in New Zealand than in Australia. In Australia the use of bleaching and improving agents is complicated since each state has its own laws, but all (I believe) permit chlorine dioxide and oxides of nitrogen; the New Zealand regulations of 1963 prohibited the use of flour improvers, and the new Food and Drug Regulations 1973 retain this prohibition (except for the use of chlorinated flour for cakes and pastry, and the permissive use of non-oxidants such as ascorbic acid). It is surely of interest that certain E.E.C. countries do not permit the oxidising agents such as chlorine dioxide and dibenzoyl peroxide; this is the case in Belgium, France, Italy, West Germany, and Luxembourg. Yet the rise in deaths just mentioned is greater in Italy than in the U.S. or Canada (where bleaching agents are permitted). In seeking to explain the unexpectedly large rise in deaths in the Netherlands and in Finland, Professor Anderson makes the serious error of suggesting that it might be caused by the increased dietary content of polyunsaturated fatty acids that arises from the use of marine oils in the manufacture of margarine. Marine oils are almost inedible, and they are deodorised and hardened by hydrogenation of the polyunsaturated fatty acids. I have emphasised on various occasions-for instance, in your columns 7-the importance of this processing of fats rich in E.F.A. as in the manufacture of margarine. Twenty years ago I found by biological assay on rats that French margarine was a rich source, British margarine less rich, and American margarine poor 8; chemical analyses (by alkali isomerisation, which determines the number of double bonds but not their steric configuration) did not support the biological assays, and a reason was the high content of trans isomers in the American margarine (estimated by infra-red spectrophotometry for me in the Dyson-Perrins Laboratory). Hydrogenation of fats raises the melting-point by both elimination of double bonds and by cis-trans isomerisation; and with the usual low concentration of hydrogen on the surface of the nickel catalyst both geometric and positional isomerisation occurs without much loss of double bonds. The American margarine I tested was made by partial hydrogenation of all the original oil, and therefore almost all E.F.A. were lost although polyunsaturated fatty acids (isomers of E.F.A.) were present. The French margarine was made by totally hydrogenating half the original oil (which would produce a solid fat with melting-point around 60°C) and then blending this with the other half; the resulting margarine had about 25% E.F.A. and no isomers. Today fortunately there are excellent margarines on the market rich in E.F.A. 5. 6. 7. 8.

Sinclair, Sinclair, Sinclair, Sinclair,

H. M. Proc. Nutr. Soc. 1958, 17, 28. H. M. Roy. Soc. Hlth J. 1956, 77, 234. H. M. Lancet, 1959, i, 474. H. M. Lect. Sci. Basis Med. 1956-57, 6, 260.