Effect of phenobarbital on hyperlipemia in patients with intrahepatic and extrahepatic cholestasis

PEDIATRIC PHARMACOLOGY AND T H E R A P E U T I C S WilliamL.Nyhan, Editor; Harry C. Shirkey, Consultant

Effect o/phenobarbital

on hyperlipemia in patients vith intrabepatic and extrahepatic cholestas# Four children with paucity o[ intrahepatic bile ducts and one with complete extrahepatic biliary atresia were treated with phenobarbital (final dose 6 to 12 rag. per kilogram per day). Clinical improvement occurred, as mani[ested by some relie[ o[ pruritus and decrease in size and number o[ xanthomata. An average of 50 per cent reduction in total serum lipids and total cholesterol occurred, and even greater reductions in tree cholesterol and triglycerides. Serum bilirubin, transaminase, and alkaline phosphatase values were not significantly changed. There were significant improvements in lipoprot'ein electrophoretic patterns. The mechanism o[ the hypolipemic effect o[ phenobarbital was unclear. Phenobarbital is known to reduce the concentration o[ serum bile salts and to increase the hepatic excretion o[ the bile salts. The latter mechanism may be a partial explanation [or some o[ the hypolipemic effects, especially in patients with paucity o[ intrahepatic bile ducts. These data suggest that phenobarbital is help[ul in the management o[ hyperlipemia as well as o[ hyperbileacidemia and hyperbilirubinemia in cholestatic conditions.

Louie G. Linarelli, * Fay H. Hengstenberg, and Allan L. Drash, Pittsburgh, Pa.

P~ENOBAR~ITAL was first used in 1966 to enhance glucuronide conjugation in hyperbilirubinemic infants with deficient glucuronide conjugating capacity?, 2 Pheno-

Supported in part by the Renziehausen Trust Fund and United States Public Health Service Grant RR-84. From the Department o[ Pediatrics, Children's Hospital of Pittsburgh, Mercy Hospital and the University o[ Pittsburgh Schobl o[ Medicine. *Reprint address: Department ot Pediatrics, Mercy Hospital, 1400 Locust St., Pittsburgh, Pa. 15219.

barbital has also been shown to be capable of stimulating hepatic excretion of conjugated bilirubin, 3 sulfobromophthalein, 4 and 1~1I rose bengal? Recent reports demonstrate that phenobarbital decreases pruritus and jaundice and reduces serum concentration of bile salts in intrahepatic biliary atresia but not in extrahepatic biliary atresiaY' 7 Phenobarbital also stimulates both synthesis and excretion of bile acids in man. a Intrahepatic and extrahepatic bilia~2r atresia are cholestatic states which are clinically apVol. 83, No. 2, pp. 291-298

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The Journal o[ Pediatrics August 1973

Table I. Age at which symptoms or physical findings were first noted* Symptoms and physical findings Age time of study Jaundice Pruritus Xanthoma Growth retardationt

S. H. 11 2 D ~2 None 1

Hepatomegaly

2A2

2~2

4A2 ~2

Splenomegaly

7w

~2

27A2

1

L. M. 7 1 D 3 3 2

I

Patients A. M. 3 35 D 2 2

I

G. W. 4 2 D 4 4 2

I

R. M. ~2 3 D None None None

~2

2~2

None

2~2

"~AI1 ages are recorded in years or fraction of a yea~ except where designated as I) = days. tGrowth retardation is documented as less than the thh-d percentile height for age (Stuart grids).

parent as severe obstructive liver disease in early infancy. Intrahepatic biliary atresia is characterized by paucity of intrahepatic bile ducts ~ and extrahepatic biliary atresia is a condition with partial or complete extrahepatic bile duct obstruction, x~ xx With the knowledge that phenobarbital stimulates endoplasmic reticulum in which lipid synthesis occurs and that bile acids are the major catabolic product of cholesterol, we studied the effects of phenobarbital on the serum lipids of children with biliary atresias. M A T E R I A L S AND M E T H O D S Four children with intrahepatic and one with extrahepatic biliary atresia were studied at Children's Hospital and Mercy Hospital of Pittsburgh. The diagnosis was established in each patient on the basis of liver function studies, liver biopsy, and exploratory laparotomy with operative cholangiography. In four children (Patients S. H., L. M., A. M., and G. W.) there was no evidence of extrahepatic obstruction but biopsy evidence of paucity of intrahepatic bile ducts, canalicular bile stasis, and portal fibrosis with minimal inflammatory infiltration. One patient (R. M.) had complete nonoperable extrahepatie biliary obstruction. Pertinent clinical features of the patients are shown in Table I. All children had the onset of obstructive jaundice in the immediate neonatal period. Evidence of chronic obstructive liver disease was repeatedly documented by the findings of elevated serum bilirubin (mainly conjugated), transaminase, alkaline phosphatase, and lipid values prior

to this study. Pruritus, first noted at 6 months to 4 years of age, was a major disturbing clinical feature in all the children except Patient R. M., the 2-month-old infant with extrahepatic biliary atresia. Multiple xanthomata were present in three patients (L. M., A. M., and G. W.). Growth failure, noted within the first 2 years of life, was present in all patients except R. M. Hepatic enlargement, present by 3 months of life, was noted in all patients. Splenomegaly, probably the result of portal hypertension, was present in four patients (S. H., A. M., L. M., and R. M.). Clinical a n d / o r laboratory evidence for gastrointestinal malabsorption included loose foamy stools, abnormal Lipiodol and xylose absorption tests, and increased 72 hour fecal stool fat. Lipids were extracted from plasma according to the method of Fillerup and Mead, 12 total lipids were determined by the method of Bragdon, ~a total and free cholesterol as described by Sperry and Webb/4 and triglycerides by the method of Levy. 1~ Lipoprotein electrophoresis was carried out on paper according to the method of Lees and Hatch ~G using a sudan black B dye. The application of these methods to the study of normal children of various ages and a variety of pathologic conditions has been reported by us previously. 17'xs All routine laboratory studies were carried out in the general clinical laboratories of the hospitals involved, using standardized methodology. Fo'llowing inpatient evaluations, the patients (varying in age from 2 months to 11 years) were given phenobarbital in an initial

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Effect o[ phenobarbital on hyperlipemia

29 3

Fig. 1A. Xanthoma on right elbow of Patient

L. M. prior to phenobarbital therapy. dose of 3 to 6 mg. per kilogram per day. The patients were followed at monthly intervals for repeat routine liver function studies and fasting lipid profiles and for readjustment of phenobarbital dosage. The duration of phenobarbital therapy has varied from three to seven months. Currently the children are receiving from 6 to 12 mg. per kilogram per day. They have been maintained on a regular diet, multivitamins, and vitamin K1 (5 mg. per day) orally. Cholestyramine was not administered. RESULTS

Observations by the parents included improvement in general well being, less irritability, increased appetites, and more sociability during therapy. No adverse effects of phenobarbital were .noted and sedation was not a problem. There have been appropriate increases in height and weight for the length

Fig. lB. Xanthoma on right elbow of Patient L. M. following 6 months of phenobarbital therapy. of observation. The four children with pruritus (Table I) had partial to complete relief. The xanthomata improved in all three children in whom they were present; the two with severe xanthomata (Patients L. M. and A. M.) showed significant reduction in size of their plaques (Figs. 1A and 1B). The micropapular xanthomata of Patient R. W. cleared completely with therapy. There were no changes in jaundice or hepatosplenomegaly. There was a reduction in the number and a change in the character of stools, but laboratory data are not available to document improvement in malabsorption. Pertinent laboratory findings are summarized in Table II. Although multiple

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The Journal of Pediatrics August 1973

Table II. Effect of phenobarbital on blood lipid concentration and liver function

Therapy duration/dose*

TL TC FC EC %EC TG Bili (T/D) SGOT SGPT Alk.p'tase

S. H., 11 yr., F It ] Ct 28/12

Normal pediatric range

320-620 120-220 26-30% of TC >70% of TC >70 50-150 <1 <50 <50 2.8-6.7

1,210 380 130 250 66 285 2.0/1.8 140 175 19

883 270 80 190 70 75 3.8/3.6 98 98 19

*All lipid concentrations are expressed in m g . / 1 0 0 ml. of plasma: T L = cent, Alk.p'tase -~ alkaline phosphatase in Bessy-Lowry-Brock units. 1~ "H =

~

total lipid, T C =

L . M . , 7 yr., F I I C 24/10

2,240 660 520 140 20 822 6.7/4.4 280 225 22 total cholesterol, FC =

900 280 140 140 50 100 4.4/4.1 240 101 22 free cholesterol,

initial concentrations just prior to phenobarbital therapy, C = current concentration: Duration of phenobarbital therapy in

++Patient with extrahepatic biliary atresia. w

values for the 4 patients with intrahepatic biliary atresia (S. H . , L. M., A. M., and R. W . ) .

blood specimens were obtained prior to and at monthly intervals after initiation of phenobarbital therapy, only the values immediately prior to therapy and those obtained during the last clinic visit are presented. Interval determinations showed some fall in lipid values at the first month with further decline as phenobarbital dosage and duration of therapy increased. In each patient there has been a fall in total lipid, total cholesterol, free cholesterol, and triglyceride values. Phospholipid, "estimated by difference"* and directly determined on a few specimens, also declined dramatically. The plasma cholesterol esters, expressed in milligrams per 100 ml., was unchanged while the per cent esterification of cholesterol increased because of an absolute fall in free cholesterol. The mean values show an approximate 50 per cent fall in total lipid and total cholesterol with a much greater fall in free cholesterol and triglyceride. Liver function studies are shown in Table I I ; although a definite trend toward decreasing values was observed, variations occurred with each test. The lipoprotein electrophoretic findings just prior to initiation of therapy with phenobarbital are compared in Fig. 2 with the *Phospholipid = total lipid esters + triglyceride).

(cholesterol + cholesterol

findings at the time of the most recent evaluation, following a period of several weeks of continuous phenobarbital administration; the pattern of a normal child is included. In the normal, healthy child studied after an overnight fast, no chylomicrons are demonstrable. The first distinctly staining band is that of beta lipoprotein, the principal carrier of cholesterol. This is followed by a much more lightly staining band, the prebeta lipoprotein which carries primarily triglyceride and is frequently not visible on lipoprotein electrophoresis in serum from normal children. Two later bands are usually seen, referred to as alpha-1 and alpha-2. Alpha lipoprotein (the high-density lipoprotein) is the primary carrier of phospholipid. In patients with clinical jaundice, a yellow pigmentation, probably bilirubin bound to albumin, is frequently noted in the alpha-2 area. All five patients had grossly abnormal lipoprotein electrophoretic patterns prior to therapy with phenobarbital (Fig. 2). There were several types of abnormalities, including increased beta lipoprotein, increase in both beta and prebeta lipoprotein, the presence of what may be abnormal lipoproteins, and a decrease in the staining of alpha lipoprotein. In each instance following administration of phenobarbital, there was an improvement of the lipoprotein pattern consisting of a de~

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Effect o/ phenobarbital on hyperlipemia

295

Patient, age, sex

A. M., 3 yr., M

I 2,540 760 604 156 20 911 10.0/6.6 510 320 19 EC

=

I C 24/9.6 869 320 164 156 51 120 4.0/2.8 328 290 20

R. W., 4 yr., M

I 1,270 472 235 237 50 180 <1 153 170 27

I C 10/6 1,120 390 118 272 70 65 <1 254 225 25

R. M.,~ 5 too., M

I 1,428 440 300 140 30 490 6.6/4.4 160 68 13

rag. per cent and per cent of total cholesterol esterified, T G

=

I

Mean IBAw

C 12/6 740 227 100 127 56 95 7.0/4.1 228 59 29

triglyceride, Bili ( T / D )

I 1,815 568 372 196 39 550 4.9/3.4 271 223 22 =

I

C 943 315 125 190 60 90 3.3/2.8 230 179 22

Bilirubin t o t a l / d i r e c t nag. per

weeks and dosage in m g . / K g . / d a y .

crease in the intensity of the beta and prebeta staining and increase in the alpha regions. Patient S. H. had a dramatic improvement in her lipoprotein electrophoretic pattern. Prior to phenobarbital therapy, Patients L. M. and A. M. demonstrated intense staining at the point of application, suggesting the presence of chylomicrons. However, the sera were not lipemic, and fat did not rise to the surface on standing, suggesting that these lipids were held in solution by a material that did not move in an electric field. Patient R. M., the child with extrahepatic biliary atresia, had a nondiscrete stain appearing-just prior to the heavy beta lipoprotein which was consistent with lipoprotein X. DISCUSSION Both extrahepatic and intrahepatic biliary atresia, have clinical features in early infancy of obstructive jaundice, pruritus, xanthoma, growth failure, and malabsorption. Cholestasis with conjugated hyperbilirubinemia, hyperbileacidemia, and hyperlipemia are characteristic laboratory features. O u r experience with these five children with biliary atresia suggests that phenobarbital ,nay be a valuable therapeutic agent in their management. Improvement in clinical features ineludes relief of pruritus, diminution of xanthomata, improvement in stool character, and lowering in serum lipid concentrations

with improvement in the lipoprotein electrophoretic findings of all children. The biliary atresias are probably not developmental anomalies. Neither extrahepatic nor intrahepatic biliary atresia is seen in aborted fetuses, stillbirths, or premature infants. Obliteration of bite ducts probably occurs during the first weeks of life? ~ 2(, Current theories of the etiology of extrahepatic atresia include vascular insufficiency to the bile ducts and sclerosing cholangitis which may be secondary to viral infection31, 2~ Good evidence indicates that intrahepatic biliary atresia is not a single pathologic entity and may arise from a number of conditions, some of which may be heritable. 2a-2~ Intrahepatic biliary atresia has occurred as a familial entity in Norwegians in association with abnormal lymphatics of the lower extremities and peripheral edema-~ a congenital defect in hepatic lymphatic vessels is suspected in this disorder. Byler's disease, a form of intrahepatic biliary atresia found in an Amish kindred, is felt to be a genetic defect in hepatic excretion of conjugated bile acids, conjugated bilirubin, and sulfobromophthalein across the bile canalicular membrane34 Other abnormalities of bile acid metabolism may be involved in the etiology of intrahepatic biliary atresiaY 62s Two patients with intrahepatic biliary atresia were found to have incomplete con-

2 96

LinarelIi, Hengstenberg, and Drash

.....

The Journal of Pediatrics August 1973

e ~3~t"

~

Fig. 2. Lipoprotein electrophoretic (LPE) pattern prior to and following phenobarbital therapy. These patterns correspond in time with the lipid data in Table II. See text for detailed description. Norm ~ normal control, O ~ origin, fl ~ beta, Prefl ~ prebeta, A1 ~ Mpha-1, A~ ~- alphas2. version of trihydroxycoprostanic acid to cholic acid, and the possible role of this intermediate bile acid in the etiology of intrahepatic biliary atresia remains to be studied. 2~ Lithocholic acid, a secondary bile acid which has been found to accumulate in infants with cholestatic conditions, may be responsible for progressive bile duct damageYT, ~s Chronic liver disease is frequently characterized by alterations in the concentration of lipids in blood. Biliary obstruction results in increase in the concentration of total and free cholesterol, triglyceride, and phospholipid. 29 The per cent of esterified cholesterol is disproportionately decreased? ~ Changes in lipoproteins parallel the lipid changes with increase in beta and prebeta lipoprotein and diminished alpha lipoprotein. Abnormal proteins such as lipoprotein - X may occur, a frequent finding in complete biliary obstruction. 29 The mechanisms of hyperlipemia in

liver disease are not well understood. Biliary obstruction, in both experimental animals and man, is associated with increased synthesis of sterols and lipids, sl-s3 Esterification of cholesterol probably takes place in the serum under the influence of the enzyme lecithin cholesterol acyl transferase? ~ This enzyme is produced in the liver and may be low in liver disease, explaining in part the abnormal ratio of esterified to unesterified cholesterol, s~ This is the first report, to our knowledge, describing the hypolipemic effect of phenobarbital. In short-term studies in rats, no changes in circulating levels of cholesterol, triglycerides, or phospholipids have been noted, a4 However, chronic administration of phenobarbital to mice and rats results in approximately 50 per cent reduction in all three lipids? 5 The possible mechanisms of phenobarbital action on lipid metabolism include changes in biosynthesis, catabolism, excretion, and absorption. In regard to cho-

Volume 83 Number 2

lesterol metabolism, the most likely possibility appears to be enhanced catabolism. Chronic a d m i n i s t r a t i o n of p h e n o b a r b i t a l to W i s t a r rats stimulates the hepatic microsomal enzyme, cholesterol 7c~-hydroxylase, which is the first a n d rate-limiting step in conversion of cholesterol to bile acids, s~ Bile acids are the m a j o r catabolic a n d excretory p r o d u c t of cholesterol; p h e n o b a r b i t a l significantly increases bile acid synthesis in primates s7 and increases biliary excretion in man. s T h e effect of p h e n o b a r b i t a l on cholesterol biosynthesis in m a n is unknown. I n animals, p h e n o b a r b i tal can enhance in vitro hepatic a n d gastrointestinal mucosal synthesis of cholesterol.SS, s.~ N o r m a l l y the e n t e r o p h e p a t i c circulation of cholesterol serves as a feedback regulating mechanism for hepatic cholesterol synthesis. Slight increases in concentrations of cholesterol in the intestinal lymphatics returning to the liver inhibit hepatic cholesterol synthesis, s2 T h u s it m a y be hypothesized t h a t in vivo e n h a n c e d gastrointestinal cholesterogenesis m a y play a role in the feedback inhibition of hepatic synthesis. A l t h o u g h a study in primates a* suggests that p h e n o b a r b i tal stimulates biliary secretion of bile salts and phospholipids, a n d decreases cholesterol secretion, the effect of p h e n o b a r b i t a l on cholesterol secretion in m a n is unknown. T h e fall in p l a s m a lipid concentration in our patients with e x t r a h e p a t i c biliary atresia is of p a r t i c u l a r i m p o r t a n c e since o t h e r investigators were unable to d e m o n s t r a t e lowering of bile salts in similar patients2, 7 This observation suggests that either p h e n o b a r b i t a l stimulation of cholesterol d e g r a d a t i o n does not d e p e n d on biliary excretion of bile salts which could a c c u m u l a t e in other b o d y pools, or intestinal stimulation of cholesterogenesis, as suggested above, is of p r i m a r y importance. Recently, investigations have shown that the action of p h e n o b a r b i t a l on bile salt m e t a b olism m a y be d e p e n d e n t on the type of liver pathology. 7 T h e t h e r a p e u t i c value of the hypolipemic effect(s) of p h e n o b a r b i t a l must await longer observation in patients to determine sustained or long-term effects. A logical extension of these observations is the study of the hypo-

Effect o/ phenobarbital on hyperlipemia

297

lipemic effect of p h e n o b a r b i t a l in o t h e r conditions. Studies are in progress to evaluate its effect in hyperlipemic states associated with early atherosclerotic disease. REFERENCES

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