Hyperbilirubinemia In Newborns Research Articles

Management of hyperbilirubinemia in the healthy term newborn.

This month's clinical practice guideline review is on hyperbilirubinemia in healthy term newborns. Due to the large number of newborns that experience clinical jaundice each year in the United States and the controversy that continues to surround the treatment of hyperbilirubinemia in healthy newborns, this guideline should be of great interest to nurse practitioners that treat this population.

Hyperbilirubinemia in healthy neonates with glucose-6-phosphate dehydrogenase deficiency.

A cohort study was carried out to assess the association between glucose-6-phosphate dehydrogenase (G6PD) deficiency, diagnosed by quantitative enzyme assay, and neonatal hyperbilirubinemia, defined as serum total bilirubin >/=15 mg/dl, in the well-baby nursery of Chang Gung Children's Hospital. Among 42,110 inborn infants, 757 male (3.54%) and 326 female (1.57%) newborns were G6PD-deficient. Compared to the occurrence of hyperbilirubinemia in G6PD-normal newborns (1.41% in male, 1.44% in female) in the well-baby nursery, a significantly higher incidence was observed in both G6PD-deficient male (11.36%) and female (7.06%) newborns. Further analyses demonstrated that the enzyme activity of G6PD in G6PD-deficient male newborns with hyperbilirubinemia (1.56+/-1.37 U/g Hb) were significantly lower than the subjects without hyperbilirubinemia (2.01+/-1.7 U/g Hb). No significant difference was observed in G6PD-deficient female newborns with hyperbilirubinemia (6.91+/-2.76 U/g Hb) compared to those without hyperbilirubinemia (7.81+/-2.84 U/g Hb). These data suggest that the G6PD-deficient neonates are at increased risk for hyperbilirubinemia even in the nursery free from agents that can potentially cause hemolysis to G6PD-deficient red cells. The lower G6PD enzyme activity was associated with the neonatal hyperbilirubinemia in G6PD-deficient male neonates.

Jaundice technologies: prediction of hyperbilirubinemia in term and near-term newborns.

Jaundice technologies: prediction of hyperbilirubinemia in term and near-term newborns.

Phototherapeutic apparatus based on an argon laser for the treatment of hyperbilirubinemia in newborns

Phototherapeutic apparatus based on an argon laser for the treatment of hyperbilirubinemia in newborns

Neonatal cholestasis

OBJECTIVE: To warn pediatricians about the early recognition of cholestasis in newborns and infants. METHODS: A bibliographic research about cholestasis was performed using Medline, and emphasizing the most relevant publications of the last 30 years. RESULTS: The concept of cholestasis and the causes of cholestatic tendency in newborns and infants are described. Several causes of intra and extrahepatic cholestasis are reported as well. In this review, only the diseases with diagnostic, therapeutic or prognostic peculiarities are commented, including extrahepatic biliary atresia, idiopathic neonatal hepatitis, galactosemia, and Alagille s syndrome. Furthermore, several resources are discussed for the diagnosis of cholestasis. CONCLUSIONS: The establishment of the diagnosis of cholestasis through the detection of hyperbilirubinemia in newborns who present jaundice after 14 days of life is a goal that could change the prognosis of several diseases responsible for neonatal cholestasis.

Recent Developments in the Management of Neonatal Hyperbilirubinemia

After completing this article, readers should be able to: 1. Describe the morbidity associated with exchange transfusion used to treat neonatal hyperbilirubinemia. 2. Explain how phototherapy affects bilirubin. 3. Describe potential toxicities of phototherapy. 4. Explain the role of carboxyhemoglobin in hemolysis. 5. Delineate the guidelines for administering intravenous immunoglobulin to healthy ABO-incompatible Coombs-positive neonates. 6. Describe the action of protoporphyrins on bilirubin. Recent clinical trends toward early discharge coupled with a new, more relaxed, “kinder, gentler approach” to the treatment of newborn hyperbilirubinemia have thrust concerns about bilirubin-related toxicity once again to the forefront of neonatologists’ consciousness. In recent years we even have witnessed a resurgence of kernicterus, which had been rendered almost nonexistent in the 1970s and 1980s. Although exchange transfusion is the oldest and most effective method of treating hyperbilirubinemia, mortality associated with this therapy has been reported to be between 0.3% and 1.2% in healthy infants and as high as 10% to 25% in sicker preterm infants. Furthermore, potential morbidity related to exchange transfusion remains significant and includes anemia, apnea, bradycardia, hypothermia, sepsis, necrotizing enterocolitis, thromboembolic phenomena, graft versus host disease, transient metabolic abnormalities, and thrombocytopenia. Accordingly, it behooves us to re-evaluate other therapeutic modalities for hyperbilirubinemia that may be equally efficacious but less invasive. Ever since the 1950s, when Sister Ward of Rochford General Hospital in Essex noted that a jaundiced baby’s skin had “faded” in natural sunlight, physicians have been searching for artificial light sources that might be used safely to treat neonatal hyperbilirubinemia. Phototherapy, which has become the standard of care, has had such a dramatic impact that a recent editorial raised the concern that exchange transfusions are becoming extinct and lamented the fact that future generations of house officers may not receive adequate training in this procedure. Under the effects of phototherapy light with maximal irradiance in the …

Pediatricians' awareness of and attitudes about four clinical practice guidelines.

The increasing complexity of medical care and a desire to increase quality and control costs have led to growing use of clinical practice guidelines (CPGs). It is unclear how helpful these guidelines are to the practitioners expected to use them. We surveyed pediatricians about their knowledge and impressions of four well-publicized CPGs: the American Academy of Pediatrics' "Practice Parameter for Hyperbilirubinemia in Newborns" (hyperbilirubinemia), "A Guideline for the Management of Febrile Infants" (fever), the Agency for Health Care Policy and Research's "Guideline for Otitis Media With Effusion" (otitis), and the US Preventive Services Task Force Guide to Clinical Preventive Services (preventive care). 1) What percentage of practicing pediatricians are aware of these guidelines? 2) How helpful do they find them? 3) What are practitioners' perceived limitations of these guidelines? 4) Have these guidelines affected provider behavior? 5) Are there features of a provider's training or practice that are associated with changing practice as a result of guidelines? A national survey of 600 pediatricians selected at random from the American Medical Association master file. A total of 300 of 555 eligible participants (54%) returned surveys. Of the respondents, 66% were aware of the hyperbilirubinemia guideline, 64% of the fever guideline, 50% of the otitis guideline, but only 16% knew of the preventive care guidelines. Mean helpfulness scores (1 to 10 scale, where 1 = "not at all helpful" and 10 = "extremely helpful") ranged from 3.67 to 6.67 for the different guidelines. In terms of limitations, 15% to 33% of respondents reported that CPGs were "too cookbook," 6% to 19% reported that they were "too time-consuming," and 4% to 16% reported that they were "too cumbersome." Additional reported limitations were believing that a guideline left no room for personal experience and judgment, concern of increased liability risk, and poor parental acceptance of CPG recommendations. The proportions reporting change in management as a result of a CPG were 28% for the hyperbilirubinemia guideline, 36% for the fever guideline, 19% for the preventive care guidelines, and 28% for the otitis guideline. Mean helpfulness scores reported by nonuniversity-affiliated physicians were significantly higher than those reported by university-affiliated physicians. In a regression model of respondents aware of a particular guideline, more recent graduation from medical school and increased helpfulness scores were associated with guideline-related behavior change. In their present form, CPGs are not perceived as very helpful by most practitioners. More recent medical school graduates and nonuniversity-affiliated physicians are more likely to find them helpful and more likely to change their behavior because of them.

Control of severe hyperbilirubinemia in full-term newborns with the inhibitor of bilirubin production Sn-mesoporphyrin (SnMP) • 1067

Control of severe hyperbilirubinemia in full-term newborns with the inhibitor of bilirubin production Sn-mesoporphyrin (SnMP) • 1067

Personal reflections on the AAP practice parameter on management of hyperbilirubinemia in the healthy term newborn.

1. Lawrence F. Nazarian, MD* 2. William O. Robertson, MD† 1. 2. *Associate Editor 3. 4. †Professor of Pediatrics Children’s Hospital and Medical Center University of Washington Seattle, WA In the July 1997 issue of Pediatrics in Review, we presented a synopsis of the American Academy of Pediatrics’ (AAP’s) practice parameter on gastroenteritis. Our intent has been to publish similar summaries of all of the published parameters, attempting to bring these guidelines to the attention of readers who are not familiar with them . The second practice parameter to be published dealt with the management of hyperbilirubinemia in normal newborns .1(1) This parameter has stimulated more discussion than any of the others published to date, primarily because the body of data available on this subject is difficult to interpret, making consensus an important element in the formation of any conclusions. Consensus is not the same as unanimity . One of the authors of that document is Dr William Robertson, who also served as the first chair of what has evolved into the Committee on Quality Improvement. Rather than providing a synopsis of the parameter, we have chosen to present some of Robertson’s personal reflections, which include many of the elements of the parameter, as well as a table that summarizes the recommendations for therapy. Not only do Robertson’s remarks provide food for thought on the subject of neonatal jaundice, but they lead the reader into a consideration of the entire quality assurance initiative. The words of a down-to-earth, articulate spokesman who has been part of the history of this movement are worth heeding. These thoughts are those of one individual, but they remind us that all recommendations ultimately come from real people who struggle with the problem of guiding clinicians while using data that could be more complete . Now in print for more than 3 years, the parameter on jaundice is being re-evaluated. All of the guidelines will undergo similar review over time. Until a revised version …

Trends in neonatal exchange transfusions at Yodogawa Christian Hospital.

A review was conducted to determine the trends in exchange transfusion (ET) of newborn infants at the Yodogawa Christian Hospital during the past 18 years. At that hospital in 1957, the first ET was performed on a term infant with severe hemolytic jaundice caused by rhesus factor (Rh) incompatibility. By 1989, ET had been performed in more than 1400 newborn infants. These cases of newborns who had had ET were retrospectively reviewed, with a focus on every 3 year period from 1974 to 1992. The total number of infants requiring ET noticeably decreased from 68 cases (14.0% of total admissions) in 1974 to 19 cases (6.1% of total admissions) in 1992. (chi 2, P < 0.001) There were three major significant changes in ET during those years. The first was a change in the subjects for ET. The incidence of ET for term infants showed a marked decrease, while the incidence of ET for preterm infants, especially for very low birthweight (VLBW) infants (< 1500 g), noticeably increased. The second was a change in indications for ET. There was a marked decrease in the need for ET as a result of hyperbilirubinemia, while the incidence of ET because of other etiologies, such as septicemia and/or disseminated intravascular coagulopathy, noticeably increased. The third was a change in the technical methods of ET. Now at the Yodogawa Christian Hospital, 100% of the infants are given ET with an automated peripheral two-site method, instead of the Diamond method. Although ET might still be a useful treatment for severe hyperbilirubinemia and other acute problems, the total number of ET noticeably decreased in accord with a decrease in the number of severe hyperbilirubinemia in term newborns. On the other hand, the incidence of ET in preterm infants increased relatively, accompanied by an increase in the survival of VLBW infants. The automated two-site method is the preferred technique for ET at the Yodogawa Christian Hospital, rather than the Diamond method. Further changes in ET might occur in accord with new alternative measures in future.

Urinary enzyme changes in newborns with unconjugated hyperbilirubinemia.

Various changes in renal function caused by unconjugated hyperbilirubinemia in newborns have been suggested in previous reports. Disclosing an injury in renal tubulus epithelium is feasible by measurement of urinary enzymes. Thus, renal function tests and urinary enzymes in 25 terms newborns with unconjugated hyperbilirubinemia were evaluated before and after phototherapy. Ten healthy term newborns without hyperbilirubinemia formed the control group. Mean values of the variables obtained before and after phototherapy in the study group and in the controls were, respectively: urine osmolality (osm/kg H2O): 0.147 +/- 0.009, 0.174 +/- 0.011, and 0.153 +/- 0.018; endogenous creatinine clearance (mL/min per 1.73 m2): 45.7 +/- 2.15, 46.0 +/- 1.6 and 46.7 +/- 3.9; fractional excretion of sodium (%): 1.27 +/- 0.30, 0.79 +/- 0.19 and 1.24 +/- 0.07; tubular phosphorus reabsorption (%): 85.8 +/- 3.3, 87.8 +/- 2.8 and 86.6 +/- 1.7; urinary N-acetyl-beta-D glucosaminidase/creatinine (IU/mg): 0.617 +/- 0.226, 0.574 +/- 0.214 and 0.619 +/- 0.210; fractional excretion of alkaline phosphatase (%): 0.422 +/- 0.103, 1.001 +/- 0.374 and 0.596 +/- 0.201; fractional excretion of lactic dehydrogenase (LDH; %): 0.102 +/- 0.019, 0.121 +/- 0.023 and 0.119 +/- 0.041; fractional excretion of AST (%): 0.433 +/- 0.127, 0.530 +/- 0.113 and 0.502 +/- 0.074; fractional excretion of alanine aminotransferase (ALT; %) 0.856 +/- 0.413, 1.619 +/- 1.076 and 1.066 +/- 0.366. No significant difference was found between these values before and after phototherapy in the study group, or between the values before phototherapy in hyperbilirubinemic neonates and in the control group. In conclusion, unconjugated hyperbilirubinemia up to a serum level of 18.4 mg/dL in term neonates does not seem to result in injury of normal tubulus epithelium as shown by urinary enzyme levels.

Direct Comparison of Sn-Mesoporphyrin, An Inhibitor of Bilirubin Production, and Phototherapy in Controlling Hyperbilirubinemia in Term and Near-Term Newborns

Sn-mesoporphyrin (SnMP) is a potent inhibitor of bilirubin production. In our previous studies a single dose (6 mumol/kg birth weight) significantly moderated hyperbilirubinemia and reduced phototherapy (PT) time by > 75% when administered within 24 hours of birth to preterm infants. To directly compare the efficacy of SnMP and PT for controlling hyperbilirubinemia in term and near-term infants. Two randomized, sequentially analyzed trials (Study I: male term infants; Study II: infants of both sexes and gestational age [GA] 245-265 days) were conducted. SnMP (6 mumol/kg birth weight) or PT (Phillips F20T12/BB lamps) was administered to paired infants according to strict criteria of plasma bilirubin levels and age. Time of enrollment and closure of cases and crossover, if necessary, of SnMP infants to PT or all infants to exchange transfusion were precisely defined in each pair. SnMP or PT was considered superior if the time between enrollment and closure of the case was reduced by > 24 hours over the alternative treatment or if crossover had occurred. None of the 44 SnMP-treated infants required supplemental PT. Of the 22 pairs of term infants enrolled in Study I, SnMP proved superior to PT in 20 and equal in two. Of the 20 pairs of near-term infants enrolled in Study II, SnMP was superior in 12 and PT in two; six were tied. Two SnMP-treated infants were unpaired. The PT-treated infants in Study I required an average of 33 hours of treatment; those in Study II, 48 hours. None of the enrolled infants required exchange transfusion or interruption of breast-feeding. In both studies, times between case enrollment and closure were reduced by > 30 hours in SnMP compared with PT infants; requirements for additional days of medical observation and bilirubin measurements were also significantly less in SnMP infants. A single dose of SnMP entirely supplanted the need for PT in jaundiced term and near-term newborns and significantly reduced medical resource use to monitor hyperbilirubinemia.

Practice Parameter: Management of Hyperbilirubinemia in the Healthy Term Newborn

Each year approximately 60% of the 4 million newborns in the United States become clinically jaundiced. Many receive various forms of evaluation and treatment. Few issues in neonatal medicine have generated such long-standing controversy as the possible adverse consequences of neonatal jaundice and when to begin treatment. Questions regarding potentially detrimental neurologic effects from elevated serum bilirubin levels prompt continuing concern and debate, particularly with regard to the management of the otherwise healthy term newborn without risk factors for hemolysis. Although most data are based on infants with birth weights ≥2500 g, "term" is hereafter defined as 37 completed weeks of gestation. Under certain circumstances, bilirubin may be toxic to the central nervous system and may cause neurologic impairment even in healthy term newborns. Most studies, however, have failed to substantiate significant associations between a specific level of total serum bilirubin (TSB) during nonhemolytic hyperbilirubinemia in term newborns and subsequent IQ or serious neurologic abnormality (including hearing impairment). Other studies have detected subtle differences in outcomes associated with TSB levels, particularly when used in conjunction with albumin binding tests and/or duration of exposure. In almost all published studies, the TSB concentration has been used as a predictor variable for outcome determinations. Factors influencing bilirubin toxicity to the brain cells of newborn infants are complex and incompletely understood; they include those that affect the serum albumin concentration and those that affect the binding of bilirubin to albumin, the penetration of bilirubin into the brain, and the vulnerability of brain cells to the toxic effects of bilirubin.

Vigintiphobia, Unbound Bilirubin, and Auditory Brainstem Responses

The management of nonhemolytic hyperbilirubinemia in term newborns is controversial. To evaluate the usefulness of serum unbound bilirubin concentrations (UBCs) in the management of hyperbilirubinemia, we compared the concentrations with abnormal auditory brainstem responses (ABRs). ABRs and serum UBCs in 37 hyperbilirubinemic term newborns (total bilirubin concentrations [TBCs] > or = 20 mg/dL and direct bilirubin concentrations < 2 mg/dL) were measured before treatment with either phototherapy or exchange transfusions. Eight of these newborns had blood incompatibilities. These hyperbilirubinemic newborns were divided into three groups according to the findings of ABR: group A, normal ABR (n = 18); group B, prolonged latency of wave I only (n = 8); and group C, prolonged interpeak latency of wave I-III/I-V and/or poor amplitude (n = 11). The peak TBC was significantly different between groups A and C (22.8 +/- 2.2 mg/dL and 25.4 +/- 2.5 mg/dL, respectively; P < .05), though there were no differences between groups A and B and between groups B and C. The peak UBCs in groups B (1.27 +/- 0.7 micrograms/dL) and C (1.34 +/- 0.37 micrograms/dL) were significantly higher than in group A (0.78 +/- 0.26 microgram/dL) (P < .05 and P < .01, respectively), though there was no significant difference in the peak UBC between groups B and C. Abnormal ABR findings were more clearly associated with the level of UBC at 1.0 microgram/dL than that of TBC at 23 mg/dL by multiple logistic regression analysis (odds ratio = 16.6, P = .0026, vs 4.2, P = .1272). These results suggest that measuring UBC may help in evaluating the possible risk of bilirubin encephalopathy in full-term newborns when there is vigintiphobia (fear of 20).

Control of Jaundice in Preterm Newborns by an Inhibitor of Bilirubin Production: Studies With Tin-Mesoporphyrin

Studies in vitro, in animal models, and in adult and newborn humans have demonstrated that certain tin(Sn)-porphyrins that competitively inhibit the activity of heme oxygenase, the rate-limiting enzyme in heme catabolism, reduce production of bilirubin and can thereby substantially diminish plasma levels of the bile pigment. To assess the effectiveness of increasing doses of the heme oxygenase inhibitor, Sn-mesoporphyrin (SnMP), in moderating the development of significant hyperbilirubinemia and thus the requirements for phototherapy in preterm newborns. In five randomized, blinded, placebo-controlled trials, SnMP in increasing doses from 1 mumol to 6 mumol/kg body weight was administered intramuscularly in the first 24 hours of life in preterm newborns of 210 to 251 days gestational age. "Special blue" lamps (Phillips F20T12/BB) were used for phototherapy in newborns exceeding a predetermined plasma bilirubin concentration, irrespective of study group. A total of 517 newborns were randomized in the five trials carried out sequentially over a 4-year period. SnMP in a dose-related manner significantly ameliorated the course of hyperbilirubinemia in the treated newborns of all gestational ages. With a SnMP dose of 6 mumol/kg body weight, the mean peak incremental plasma bilirubin concentration was reduced by 41% and the phototherapy requirements were decreased by 76% compared to control subjects. Erythema observed in a few SnMP-treated newborns who required phototherapy was mild, transient, and without sequelae. No other untoward effects were observed during hospitalization or at a follow-up at post-term age of 3 and 18 months. SnMP, by inhibiting the production of bilirubin, substantially moderates the development of hyperbilirubinemia in preterm newborns. This compound and similarly acting enzyme inhibitors merit further clinical study as agents for controlling neonatal hyperbilirubinemia, particularly in neonatal populations for whom other treatment modalities are not available.

Bilirubin and Other Brain Cells

Drs Newman and Maisels1 agree that the current management of hyperbilirubinemia in the term newborn is based on assumptions searching for scientific validation. As I was reading these letters I could not help but think about another "hot" topic occupying the "Letters to the Editor" section of Pediatrics—lead. As with lead-induced neurotoxicity, children practitioners cannot wait until there are data to fully guide decision making. In their article Newman and Maisels2 indicate some areas in the treatment of newborn hyperbilirubinemia in which there are wide disparities about the preferred management approach, and they identify those aspects of treatment that require a revised consensus statement to help guide therapy.

Automated Total and Neonatal Bilirubin Values in Newborns: Is a Distinction Clinically Relevant?

Guidelines for managing hyperbilirubinemia in newborns were developed by using diazo methods that measure total and direct-reacting bilirubins and calculate an indirect fraction. The automated Kodak Ektachem system allows for measuring serum bilirubin by either of two dry-slide methods: TBIL, involving a modified diazo method, and NBIL, involving a dual-wavelength colorimetric method that fractionates and directly measures the unconjugated (Bu) and conjugated (Bc) bilirubins (Bu+Bc = neonatal bilirubin). The manufacturer recommends that NBIL be used in newborns less than 15 days old, which is impractical in a large, busy hospital laboratory. We compared NBIL and TBIL in 500 paired serum samples from infants less than 15 days old. We noted a statistically significant difference between TBIL and NBIL values (162.9, SD 70.4, vs 164.6, SD 69.2, mumol/L; P less than 0.0001), which was small and of no clinical significance. We conclude that TBIL values may be used with caution for newborn bilirubin screening. Furthermore, NBIL measurements are an acceptable alternative to diazo measurements for neonatal care, allowing the use of previously developed guidelines with NBIL values.

Measurement of the Yellow Colour of the Skin as a Test of Hyperbilirubinemia in Mature Newborns

The relation between the yellow colour of the skin as measured by the Minolta Air Shields jaundice meter and the serum bilirubin concentration was investigated in 207 mature icteric, but otherwise healthy, newborns and the relationship between the changes in the meter readings and the changes in serum bilirubin concentration was studied in 99 of the infants. Good correlation was found both between the meter readings and the serum bilirubin concentration (p = 0.81), and between the changes in meter readings and the changes in serum bilirubin concentration (p = 0.69). The jaundice meter proved to be effective in predicting hyperbilirubinemia defined as serum bilirubin values 175 or 225 mumol/l, and was also effective in predicting increasing or decreasing serum bilirubin concentrations by sequential meter readings. The gestational age correlated slightly but significantly with the meter readings (p = -0.15) and with the serum bilirubin concentration (p = -0.15). However, these findings did not affect the action levels for use of the jaundice meter as a screening device for hyperbilirubinemia. The postnatal age and the birthweight did not significantly influence the meter readings.

Clofibrate Treatment of Neonatal Jaundice

To the Editor.— Kappas et al1 have reported the results of Sn-protoporphyrin use in the management of hyperbilirubinemia in full-term newborns with direct Coombs-positive ABO incompatibility. A commentary, "A New Era in Therapy for Hyperbilirubinemia,"2 emphasizes the great interest of this pharmacologic means of prevention of neonatal hyperbilirubinemia (inhibition of the transformation of heme into bilirubin) by the action of Sn-protoporphyrin on heme oxygenase. Anthony F. McDonagh in the Journal of Pediatrics shows that the efficiency of tin-porphyrin is limited and that phototoxic risks exist which should lead the authors to be cautious in current practice.3

Photophysical studies of tin(IV)-protoporphyrin: potential phototoxicity of a chemotherapeutic agent proposed for the prevention of neonatal jaundice.

The strongly light-absorbing metalloporphyrin tin(IV)-protoporphyrin IX (SnPP) is currently being considered as a chemotherapeutic agent for preventing severe hyperbilirubinemia in newborns, a condition usually treated by phototherapy with visible light. To assess the potential phototoxicity of SnPP we studied the photophysics of the drug in aqueous and nonaqueous solutions using laser flash photolysis and pulse radiolysis. Quantum yields for formation of triplet-state excited SnPP were measured, along with triplet lifetimes and extinction coefficients. In addition, we measured quantum yields for the SnPP-photosensitized formation of singlet oxygen in MeO2H and 2H2O containing cetyltrimethylammonium bromide, using a time-resolved luminescence technique. Quantum yields for formation of triplet SnPP from monomeric ground-state SnPP are high (approximately equal to 0.6-0.8), and triplet lifetimes are long (approximately equal to 0.1-0.2 ms). Efficient quenching of triplet SnPP by molecular oxygen was seen with rate constants greater than 10(9) M-1.s-1. SnPP-photosensitized formation of singlet oxygen in aqueous and nonaqueous solvents was confirmed by the detection of the characteristic luminescence at 1270 nm (phi delta = 0.58 in MeO2H). The photophysical parameters and singlet oxygen-sensitizing efficiency of SnPP are similar to those reported for hematoporphyrin and other metal-free porphyrins known to be phototoxic to humans. These observations suggest that cutaneous photosensitivity arising from singlet-oxygen damage is likely to be an undesirable side-effect of SnPP therapy.