Carbamazepine-induced non-hereditary acute porphyria

Porphyria and dementia: a case report

The porphyrias are a group of rare hereditary metabolic disorders where there is an excess formation and excretion of porphyrins or their precursors. Type IIA, acute intermittent porphyria (AIP), has an estimated prevalence of one to eight per 100,000 in the general population but is thought to have a higher prevalence in psychiatric patients. AIP can present with a variety of psychiatric symptoms, often misdiagnosed. Associated neuropathological changes including focal cerebral ischaemic lesions have been found. However, to our knowledge, no case of dementia and AIP has been described. We present the case of a 56 year old man with a five-year history of progressive cognitive decline, diagnosed with AIP at an advanced stage of dementia. Whether AIP contributed to the dementia or is a coincidental finding is unknown. However treatment of AIP in this case resulted in some improvement in the patient's cognitive state.

Non-alcoholic steatohepatitis induced by carbamazepine and variegate porphyria

A 42-year-old woman presented with acute bullous skin lesions and angio-oedema that had developed 3 months after initiation of treatment with carbamazepine for epilepsy. Chromatographic analysis of urinary porphyrins was compatible with variegate porphyria. This was manifested initially by neurological symptoms that were mistaken for epilepsy and later by cutaneous symptoms also. Histological findings excluded hepatic porphyria, but revealed severe fatty changes thought to be caused by idiosyncratic metabolism of carbamazepine. While the porphyrinogenicity of carbamazepine is well known, the presence of variegate porphyria has not been reported. The toxic hepatic effects of the drug on hepatic cytochrome P-450, which is involved in haem metabolism, could have aggravated the pre-existent porphyria, provoking the onset of skin lesions.

Prevalence of acute intermittent porphyria in a Mexican psychiatric population

BACKGROUND

Acute intermittent porphyria is a hereditary error of porphyrin metabolism in which the main metabolic defect is caused by a decrease in porphobilinogen deaminase activity. Previous work has demonstrated a higher prevalence of acute intermittent porphyria in the psychiatric patient population than in the general population. The goal of this study was evaluate 300 psychiatric patients and 150 control subjects to detect acute intermittent porphyria by measurement of porphobilinogen (PBG) deaminase activity in blood.

METHODS

Screening for porphobilinogen deaminase activity was carried out by fluorometric measurement of porphyrins synthesized during 1 h in blood and the measurement of delta-aminolevulinic acid and porphobilinogen in urine.

RESULTS

We found two psychiatric patients, one male and one female, with decreased porphobilinogen deaminase activity. When the families of these patients were studied, one brother was found to have an abnormality. Among controls, a woman was found to have the abnormality and her father was found to have typical features of the disease.

CONCLUSIONS

These results indicate a prevalence of porphyria in Mexican psychiatric patients similar to controls, and that measurement of PBG deaminase activity is a good tool for defining acute intermittent porphyria carriers.

Biochemical differentiation of the porphyrias

OBJECTIVES

To differentiate the porphyrias by clinical and biochemical methods.

DESIGN AND METHODS

We describe levels of blood, urine, and fecal porphyrins and their precursors in the porphyrias and present an algorithm for their biochemical differentiation. Diagnoses were established using clinical and biochemical data. Porphyrin analyses were performed by high performance liquid chromatography.

RESULTS AND CONCLUSIONS

Plasma and urine porphyrin patterns were useful for diagnosis of porphyria cutanea tarda, but not the acute porphyrias. Erythropoietic protoporphyria was confirmed by erythrocyte protoporphyrin assay and erythrocyte fluorescence. Acute intermittent porphyria was diagnosed by increases in urine delta-aminolevulinic acid and porphobilinogen and confirmed by reduced erythrocyte porphobilinogen deaminase activity and normal or near-normal stool porphyrins. Variegate porphyria and hereditary coproporphyria were diagnosed by their characteristic stool porphyrin patterns. This appears to be the most convenient diagnostic approach until molecular abnormalities become more extensively defined and more widely available.

The effect of therapeutic drugs and other pharmacologic agents on activity of porphobilinogen deaminase, the enzyme that is deficient in intermittent acute porphyria

Drugs and toxins precipitate life-threatening acute attacks in patients with intermittent acute porphyria. These materials may act by directly inhibiting enzyme activity, thus further reducing porphobilinogen (PBG) deaminase activity below the ca. 50% level that results from the gene defect. To test this, we studied the effects of drugs that precipitate acute attacks (lead, phenobarbital, griseofulvin, phenytoin, sulfanilamide, sulfisoxazole, 17alpha-ethinyl estradiol, 5beta-pregnan-3alpha-ol-20-one), drugs that are safe (lithium, magnesium, chlorpromazine, promethazine), and those with uncertain effects (ethyl alcohol, imipramine, diazepam, haloperidol) on activity of PBG deaminase in vitro and in vivo. In the in vitro studies, of PBG deaminase from human erythrocytes from normals and individuals with IAP, only lead (> or = .01 mM) inhibited enzyme activity. Chlorpromazine (> or = .01 mM), promethazine (> or = .01 mM) and imipramine (1 mM) seemed to increase enzyme activity. In most in vivo experiments, male rats were injected intraperitoneally with test material twice daily for 3 days and once on day four; and erythrocyte and hepatic PBG deaminase activity was assayed thereafter. Effects on enzyme activity were observed only with 17alpha-ethinyl estradiol (0.05 microg/kg/day; reduction of 11% in erythrocyte enzyme [NS], and of 20% in liver enzyme [P=.02]), and imipramine (12.5 mg/kg/day; reduction in erythrocyte enzyme activity of 13% [P<.001]). Rats given lead acetate in their drinking water (10 mg/ml) for the first 60 days of life, resulting in high blood and liver lead levels, had increased erythrocyte PBG deaminase (167% of control; P=.004). Thus, enzyme inhibition by lead in vitro was not reflected in a similar in vivo inhibition. The only inhibitory effects in vivo, with ethinyl estradiol and imipramine, appear to be mild and biologically inconsequential. We conclude that inhibition of PBG deaminase activity by materials that precipitate acute attacks is an unlikely mechanism by which these materials exert their harmful effects in patients with IAP.

[Acute intermittent porphyria associated with epilepsy in a child: diagnostic and therapeutic difficulties]

BACKGROUND

Acute intermittent porphyria is an autosomal dominant inborn error of heme biosynthesis. The diagnosis of acute porphyria is rare before puberty. Its association with epilepsy induces difficulties in diagnosis and seizure treatment.

CASE REPORT

A case of acute intermittent porphyria in a 9-year old boy with epilepsy is reported. The diagnosis was made only after the third hospitalisation, with the measurement of enzyme activity and identification of family members with latent disease. Adjustment of antiepileptic treatment was necessary 7 months later.

CONCLUSION

Most antiepileptic drugs are unsafe because they have demonstrated porphyrinogenicity. Low doses of clonazepam can be used in this situation.

Variable phenotypic expression of genotypic abnormalities in the porphyrias

The inherited porphyrias are the consequence of inherited deficiencies of enzymes in the heme synthesis pathway; they exhibit classical Mendelian inheritance patterns. The acute porphyrias (acute intermittent, porphyria variegata, hereditary coproporphyria) result from 50% (approx.) deficiencies of specific enzymes, which demonstrate autosomal dominant inheritance. However, only approx. 10% of subjects who inherit a porphyrin enzyme deficiency develop the corresponding acute porphyria and in most instances there is no obvious reason why one patient with an enzyme deficiency is symptomatic whereas another is not. Control of heme synthesis is achieved by the repressor effect of heme on the enzyme ALA synthase. Acute attacks of porphyria can be precipitated in susceptible persons by drugs, ethanol, starvation, hormones, stress and infection. The mechanism is usually by induction of ALA synthase activity. The molecular biology of porphyria variegata and hereditary coproporphyria is large unexplored. Acute intermittent porphyria is due to a partial deficiency of the enzyme porphobilinogen deaminase in the liver. The location of the gene for this enzyme has been identified on the long arm of chromosome 11. Acute intermittent porphyria is a genetically heterogenous disease with the abnormality frequently being a point mutation affecting synthesis of the enzyme.

Effects of acute carbamazepine administration on haem metabolism in rat liver

The effects of acute carbamazepine (CBZ) administration on haem metabolism in rat liver were examined in relation to the mechanism by which it exacerbates hepatic porphyrias. In a screening test for drug exacerbation of porphyria developed in this laboratory, CBZ at a very small dose (1.5 mg/kg, p.o.) behaved as an exacerbator, potentiating the loss of haem utilized by tryptophan pyrrolase (TP; tryptophan 2,3-dioxygenase; L-tryptophan-O2 oxido-reductase, decyclizing; EC 1.13.11.11) and the associated induction of activity of the rate-limiting enzyme of haem biosynthesis, 5-aminolaevulinate synthase (5-ALA-S) caused by the experimental porphyrogen 3,5-diethoxycarbonyl-1,4-dihydrocollidine. A larger dose of CBZ (50 mg/kg, i.p.) induced 5-ALA-S activity by 40-100% at 3 hr. This induction was preceded by an increase in the haem saturation of TP, and was abolished when such an increase was prevented by allopurinol. 5-ALA-S induction by CBZ was not associated with decreased turnover of the enzyme, nor with any significant changes in concentration of the major hepatic haemoprotein, cytochrome P450. It is suggested that CBZ may exacerbate the hepatic porphyrias by inducing 5-ALA-S activity secondarily to an increased utilization of haem by TP.

An unusual case of variegate porphyria with possible homozygous inheritance

We report an unusual case of variegate porphyria in a young girl with epilepsy, mental retardation and premature adrenarche. Symptoms of porphyria commenced about the age of 12 years and death occurred about 18 months later. The patient had very low protoporphyrinogen oxidase activity in her cultured fibroblasts. Both parents had half the normal activity of this enzyme in lymphocytes and are heterozygous for the abnormal gene for variegate porphyria. Therefore, it is possible that the patient was a homozygous variant. Anticonvulsant therapy and low hepatic 5 alpha reductase activity were probably other contributing factors to the severity of the condition in this patient.

Protoporphyrinaemia and decreased activities of 5-aminolevulinic acid dehydrase and uroporphyrinogen I synthetase in erythrocytes of a Vitamin B6-deficient epileptic boy given valproic acid and carbamazepine

Carbamazepine (CBMZP) has been implicated as an inhibitor of the activities of 5-aminolaevulinic acid dehydratase (ALA-D) and uroporphyrinogen I synthetase (URO-S). In an epileptic boy undergoing long-term treatment with valproic acid (VPA), 1.3 g/d, CBMZP, 0.9 g/d and folic acid, 7.5 mg/d, decreased activities of ALA-D and URO-S coincided with increased levels of erythrocyte protoporphyrin (EP) in the absence of Pb poisoning, iron depletion and erythropoietic protoporphyria. A progressive fall in plasma pyridoxal 5'-phosphate (B6-P) to 7.7 nmol/L (lower reference limit, 14.6 nmol/L) prompted implementation of pyridoxine HCl (B6-HCl), 87.5 mg/d followed by administration of both B6-HCl and preformed B6-P (50 mg/d each). This permitted the eventual withdrawal of VPA and a net reduction of CBMZP to 450 mg/d. During these manipulations, ALA-D and URO-S activities, EP and urinary porphyrins and their precursors were measured serially. An assay system utilizing red cell ALA-D for generation of porphobilinogen (PBG) from added ALA at pH 7.4 was used for determination of ALA-D and URO-S activities in separate aliquots of the same assay mixture both in the absence and presence of Zn and dithiothreitol (DTT). One unit (U) for ALA-D = 1 nmol PBG/L RBC/s; for URO-S = 1 nmol porphyrin/L/s; minimum normal level for ALA-D = 135 U; for URO-S = 6 U. B6-HCl alone entailed increases in ALA-D and URO-S prior to any reduction of CBMZP. After administration of both B6-HCl and B6-P and withdrawal of VPA, the overall increase in ALA-D was from 54.59 to 197.2 U (-Zn; -DTT) and from 50.76 to 217.3 U (+Zn; +DTT). The overall increase in URO-S was from 2.67 to 8.90 U (-Zn; -DTT) and from 3.02 to 8.66 U (+Zn; +DTT). During stepwise reduction of VPA, EP remained elevated to values as high as 2.48 mumol/L (upper reference limit, 1.33 mumol/L). Only after permanent withdrawal of VPA did concentrations of EP fall to normal levels. Values for porphyrins and their precursors in urine were normal throughout. Since both VPA and B6-P are strongly protein-bound, it is suggested that VPA displaced B6-P from protective protein binding sites and that the resulting deficit in B6-P (rather than CBMZP) reduced ALA-D and URO-S activities via primary reduction of ALA-synthetase activity. Increases in EP emerge as a hitherto unappreciated effect of VPA warranting further investigation.

Acute intermittent porphyria in two patients on anticonvulsant therapy and with normal erythrocyte porphobilinogen deaminase activity

1. Acute intermittent porphyria (AIP) is sometimes termed a 'pharmacogenetic' disease. patients with genetic deficiency of the enzyme porphobilinogen deaminase are liable to develop acute attacks of porphyria if exposed to a variety of drugs. 2. Two patients are reported who had no evidence of deficiency of erythrocyte porphobilinogen deaminase yet developed typical attacks of AIP while on anticonvulsant therapy. 3. Normal activity of erythrocyte porphobilinogen deaminase does not completely exclude porphyria. 4. Acute porphyria should be suspected if clinical deterioration occurs during therapy with anticonvulsants, or other porphyrinogenic drugs, even in the absence of an underlying genetic defect in haem synthesis in peripheral blood cells.

Effects of sodium valproate on haem biosynthesis in man: implications for seizure management in the porphyric patient

The short-term effects of sodium valproate (VPA) on haem biosynthesis were assessed in a placebo-controlled crossover trial in eight healthy male subjects who ingested VPA 500 mg t.i.d. and matched placebo for 5 days. All showed augmented activity of leucocyte 5-aminolaevulinate synthase (ALA-S) activity, the rate-limiting enzyme of the haem biosynthetic pathway, following 3 and 5 days of VPA treatment (P less than 0.001). This was accompanied by increased urinary excretion of 5-aminolaevulinic acid (ALA; P less than 0.02) and total porphyrins (P less than 0.01). Mean (+/- SD) total VPA concentrations on day 3 (89 +/- 16 mg 1-1) and day 5 (91 +/- 22 mg 1-1) were within the target range for the drug. The long-term effects of VPA administration were examined in epileptic patients on established monotherapy. Leucocyte ALA-S activity (P less than 0.001), and daily urinary excretion of porphobilinogen (P less than 0.01) and total porphyrins (P less than 0.01) were all higher than in age-matched controls. No significant differences in erythrocyte ALA-dehydratase, porphobilinogen deaminase and uroporphyrinogen decarboxylase activities were found between the groups. These data suggest that VPA is porphyrinogenic in man and cannot be recommended as safe for seizure management in the porphyric patient.

The effects of chronic carbamazepine treatment of haem biosynthesis in man and rat

The anticonvulsant drug carbamazepine has been reported to produce a condition clinically and biochemically similar to acute intermittent porphyria (AIP). We have determined the effect of chronic carbamazepine treatment on the activities of the enzymes of haem biosynthesis in circulating blood cells and on the urinary excretion of porphyrins and their precursors in 53 epileptic patients receiving monotherapy and in 42 age- and sex-matched controls. In the patients the mean activity of leucocyte 5-aminolaevulinic acid (ALA) synthase, the rate-limiting enzyme of the pathway, was 218% of control values (p less than 0.001) and ALA-dehydratase activity was reduced by 37% (p less than 0.001). Circulating carbamazepine concentrations correlated negatively with ALA dehydratase (rs = -0.45; p less than 0.01). Porphobilinogen deaminase and uroporphyrinogen decarboxylase appeared unaffected by carbamazepine treatment. Significant quantitative increases in the urinary excretion of porphobilinogen and total porphyrins (both p less than 0.05) accompanied the changes in enzyme activity. Similar dose-dependent effects on ALA synthase and ALA dehydratase were shown to occur in rats treated for 5 days with 3 different doses of carbamazepine. These findings further support the porphyrinogenicity of carbamazepine, but the pattern of enzyme alteration differs from that found in AIP.

The risk-benefit ratio of anticonvulsant drugs

The concepts underlying the notion of a risk-benefit ratio for anticonvulsant therapy have determined the development of the drug treatment of epilepsy over many years. The risk element in the ratio arises from the various possible physical and psychological adverse effects of anticonvulsant therapy; the benefit is derived from the capacity of therapy to prevent seizures and thus reduce the disadvantages which result from having epilepsy. The physical adverse effects of anticonvulsant therapy may involve many tissues and organs. The drugs tend to depress cerebral, cerebellar and brain stem function, and may slow peripheral nerve conduction. Prolonged intake may cause hypocalcaemia and osteoporosis, folate depletion, various haematological and immunological abnormalities, and overgrowth of subcutaneous and gingival tissues. Idiopathic reactions may involve the skin, lymph nodes, liver, pancreas, kidney and thyroid, and cause electrolyte disturbances, while maternal anticonvulsant intake during pregnancy may be associated with an increased incidence of fetal malformations. Local reactions may occur at drug administration sites, and anticonvulsants may interact pharmacokinetically and pharmacodynamically with co-administered drugs. The taking of anticonvulsants sometimes has undesirable psychological effects on both the patient and his or her family. Epilepsy itself often results in adverse psychological consequences which emanate from the uncertainty and insecurity that is imposed by the unpredictable occurrence of seizures, from the limitations epilepsy sets on the patient's lifestyle and employment prospects, and from unfavourable community attitudes towards the disorder. Contemporary anticonvulsant therapy is not fully effective in all patients, but to the extent that it can control seizures it may help alleviate these emotional burdens that are a result of epilepsy. The consensus of present day medical opinion is that, in the great majority of clinical situations, the benefits of anticonvulsant therapy outweigh the disadvantages. However, to provide optimal management for individual patients, the risk-benefit ratio of therapy must be repeatedly assessed at all stages of a patient's treatment, and therapeutic decisions taken in the light of the ratio as it applies to the individual.

The influence of carbamazepine on the heme biosynthetic pathway

Carbamazepine, a drug which is widely used in neurological diseases, has a porphyrogenic effect in chick embryo liver cells in culture. It increased the concentration of cellular porphyrins by 80-fold and delta-aminolevulinate synthase activity by 4-fold. The increase in the accumulation of porphyrins preceded that of ALAS activity. Measurements of the activities of aminolevulinate dehydrase, porphobilinogen deaminase, and uroporphyrinogen decarboxylase showed that C inhibits UROD up to nearly 50% and PBGD activity up to 20%, but does not affect the activity of ALAD. The pattern of accumulation of porphyrins, mainly uro- and heptacarboxylporphyrin, is compatible with an inhibition of UROD. We may, therefore, conclude that the porphyrogenic effect of C in monolayers of chick embryo liver cells is the result of its inhibitory effect on the activity of UROD.

The use of carbamazepine as an adjunctive medication in the treatment of affective disorders: a clinical report

This is a report of an open clinical trial of Carbamazepine in the treatment of patients who suffered from affective disorders and who did not have an adequate response to Lithium or other medications. Our findings suggest that Carbamazepine can be a useful adjunctive medication when used in combination with Lithium and other psychotropic medications. The characteristics of the patients who responded were examined. The clinical state of the patients at the point of intervention varied; eight patients were manic and four patients were depressed. Four patients were judged to have had markedly effective responses, four showed an effective response and in four there was a slightly effective response. From the duration of the trials it was evident that in cases where Carbamazepine produced a good response its effect was seen as early as two weeks. The mean daily dose used varied from 300-1300 mgs. Because of the open nature of this trial, Carbamazepine was not withdrawn except in one instance.

Effects of cimetidine on carbamazepine auto- and hetero-induction in man

The effect of cimetidine (CMT; 400 mg twice daily) and matching placebo on the enzyme-inducing properties of carbamazepine (CBZ; 200 mg at night for 15 days) was studied in seven healthy male volunteers. CMT alone had no significant effect on antipyrine kinetics, urinary 6 beta-hydroxycortisol excretion or leucocyte delta-aminolaevulinic acid synthase (ALA.S) activity. CBZ increased leucocyte ALA.S activity by 204% following 1 week's treatment (P less than 0.001). Thereafter, ALA.S activity fell despite continued CBZ administration. Concomitant CMT did not influence this response. Antipyrine clearance and urinary 6 beta-hydroxycortisol excretion were both increased by CBZ after 2 weeks' treatment (P less than 0.01). CMT blocked CBZ induction of antipyrine metabolism but the rise in urinary 6 beta-hydroxycortisol excretion was unaffected. Plasma CBZ concentrations 10, 14 and 18 h following the 8th and 15th doses were higher when CMT was taken concurrently (P less than 0.05). CBZ half-life fell by 36% and clearance rose by 29% (both P less than 0.001) with placebo and by 10% and 7% (both NS) when CMT was taken concurrently. CMT inhibits CBZ auto- and hetero-induction in man. Epileptic patients receiving CBZ chronically may be at risk of toxicity if CMT is also prescribed.

Effect of carbamazepine on haem biosynthesis in man

The effects of the enzyme-inducing anticonvulsant carbamazepine on haem biosynthesis in healthy male subjects is reported. A dose-dependent increase in the activity of leucocyte delta-aminolaevulinic-acid synthase, the rate-limiting enzyme of haem biosynthesis, was noted following 400 and 600 mg carbamazepine daily in the same eight subjects. This rise was maximal after 1 week's treatment (400 mg: 509% +/- 285 of baseline; 600 mg: 1062% +/- 170 of baseline; P less than 0.01). Values fell from this peak during the second week despite continuing carbamazepine administration. This pattern was confirmed in a further six subjects taking carbamazepine 400 mg daily for 3 weeks in whom more frequent enzyme measurements were made. The activity of uroporphyrinogen-1-synthase in the erythrocyte fell by 10-15% during the treatment periods (P less than 0.01). Uroporphyrin and penta-, hexa- and hepta-carboxylic porphyrins appeared in the urine of all subjects during CBZ therapy. Changes in daily urinary porphyrin and precursor excretion were inconsistent. CBZ is a porphyrinogenic drug which mimics the changes in enzyme activities and urinary porphyrin ester profile found in patients with latent acute intermittent porphyria, who have a genetic deficiency in uroporphyrinogen-1-synthase activity. Leucocyte delta-aminolaevulinic-acid synthase may provide a suitable in vivo system for testing the porphyrinogenicity of drugs in man.

Effect of stanozolol on delta-aminolaevulinic acid synthase and hepatic monooxygenase activity in man and rat

Stanozolol is an anabolic steroid which is used in the treatment of aplastic anaemia and has been recently advocated for the prophylaxis of vascular thrombosis. Similar steroid substances stimulate the activity of delta-aminolaevulinic acid synthase (ALA S), the rate limiting enzyme of haem biosynthesis, in rat hepatocytes and chick embryo liver cell cultures and activate acute hepatic porphyria. In the present study stanozolol (10 mg daily for 14 days) has been shown to increase significantly leucocyte ALA S activity in 9 healthy male subjects. There was a concomitant rise in urinary ALA and total porphyrin excretion but no change in antipyrine kinetics or urinary 6 B hydroxycortisol excretion. In a complementary study in male Sprague Dawley rats, stanozolol administered intraperitoneally, produced a dose-dependent increase in hepatic ALA S activity without changing hepatic cytochrome P 450 content. Stanozolol has been clearly shown to elevate ALA S activity, probably directly, and thereby, porphyrin production without affecting hepatic monooxygenase activity. This porphyrinogenic effect may be relevant to the successful treatment of aplastic anaemia with anabolic steroids. Leucocyte ALA S activity may provide a human system for the study of drug porphyrinogenicity in vivo.