Application of Caco-2 cell line in herb-drug interaction studies: current approaches and challenges.

The Caco-2 model is employed in pre-clinical investigations to predict the likely gastrointestinal permeability of drugs because it expresses cytochrome P450 enzymes, transporters, microvilli and enterocytes of identical characteristics to the human small intestine. The FDA recommends this model as integral component of the Biopharmaceutics Classification System (BCS). Most dedicated laboratories use the Caco-2 cell line to screen new chemical entities through prediction of its solubility, bioavailability and the possibility of drug-drug or herb-drug interactions in the gut lumen. However, challenges in the inherent characteristics of Caco-2 cell and inter-laboratory protocol variations have resulted to generation of irreproducible data. These limitations affect the extrapolation of data from pre-clinical research to clinical studies involving drug-drug and herb-drug interactions. This review addresses some of these caveats and enumerates the plausible current and future approaches to reduce the anomalies associated with Caco-2 cell line investigations focusing on its application in herb-drug interactions.

Para-aminosalicylic acid plasma concentrations in children in comparison with adults after receiving a granular slow-release preparation.

There are no paediatric data regarding slow-release para-aminosalicylic acid (PAS). We studied PAS plasma concentrations in 10 children receiving a single 150 mg/kg dose daily or 75 mg/kg twice daily and 12 adults receiving 4 g twice daily. Blood specimens pre-dose and 2, 4, 6, 8 and 12 h post-dose from the children and 2, 3, 4, 5, 6, 8 and 12 h post-dose from the adults were analysed by high performance liquid chromatography MS/MS. The mean Cmax in children receiving PAS 75 mg/kg and 150 mg/kg and adults receiving 4 g was 45.40, 56.49 and 51.3 µg/ml, respectively (p = 0.614); the AUC0-12 was 233.3, 277.9 and 368.0 µg/h/ml (p = 0.587). No parameters differed significantly between children and adults nor between the two doses in the same children. A 150 mg/kg PAS dosage given as one or two daily doses leads to plasma concentrations in children similar to those of adults receiving 4 g PAS twice daily.

Pharmacokinetics of ethionamide in children.

Ethionamide (ETH), a second-line antituberculosis drug, is frequently used in treating childhood tuberculosis. Data supporting ETH dose recommendations in children are limited. The aim of this study was to determine the pharmacokinetic parameters for ETH in children on antituberculosis treatment including ETH. ETH serum levels were prospectively assessed in 31 children in 3 age groups (0 to 2 years, 2 to 6 years, and 6 to 12 years). Within each age group, half received rifampin (RMP). Following an oral dose of ETH (15 to 20 mg/kg of body weight), blood samples were collected at 0, 1, 2, 3, 4, and 6 h following 1 and 4 months of ETH therapy. The maximum serum concentration (C(max)), time to C(max) (T(max)), and area under the time-concentration curve from 0 to 6 h (AUC(0-6)) were calculated. Younger children were exposed to lower ETH concentrations than older children at the same mg/kg body weight dose. Age correlated significantly with the AUC after both 1 month (r = 0.50, P = 0.001) and 4 months (r = 0.63, P = 0.001) of therapy. There was no difference in the AUC or C(max) between children receiving concomitant treatment with RMP and those who did not. Time on treatment did not influence the pharmacokinetic parameters of ETH following 1 and 4 months of therapy. HIV infection was associated with lower ETH exposure. In conclusion, ETH at an oral dose of 15 to 20 mg/kg results in sufficient serum concentrations compared to current adult recommended levels in the majority of children across all age groups. ETH levels were influenced by young age and HIV status but were not affected by concomitant RMP treatment and duration of therapy.

Pharmacokinetics of isoniazid, rifampin, and pyrazinamide in children younger than two years of age with tuberculosis: evidence for implementation of revised World Health Organization recommendations.

The World Health Organization (WHO) recently issued revised first-line antituberculosis (anti-TB) drug dosage recommendations for children. No pharmacokinetic studies for these revised dosages are available for children <2 years. The aim of the study was to document the pharmacokinetics of the first-line anti-TB agents in children <2 years of age comparing previous and revised WHO dosages of isoniazid (INH; 5 versus 10 mg/kg/day), rifampin (RMP; 10 versus 15 mg/kg/day), and pyrazinamide (PZA; 25 versus 35 mg/kg/day) and to investigate the effects of clinical covariates, including HIV coinfection, nutritional status, age, gender, and type of tuberculosis (TB), and the effect of NAT2 acetylator status. Serum INH, PZA, and RMP levels were prospectively assessed in 20 children <2 years of age treated for TB following the previous and the revised WHO dosage recommendations. Samples were taken prior to dosing and at 0.5, 1.5, 3, and 5 h following dosing. The maximum drug concentration in serum (C(max)), the time to C(max) (t(max)), and the area under the concentration-time curve (AUC) were calculated. Eleven children had pulmonary and 9 had extrapulmonary TB. Five were HIV infected. The mean C(max) (µg/ml) following the administration of previous/revised dosages were as follows: INH, 3.19/8.11; RMP, 6.36/11.69; PZA, 29.94/47.11. The mean AUC (µg·h/ml) were as follows: INH, 8.09/20.36; RMP, 17.78/36.95; PZA, 118.0/175.2. The mean C(max) and AUC differed significantly between doses. There was no difference in the t(max) values achieved. Children less than 2 years of age achieve target concentrations of first-line anti-TB agents using revised WHO dosage recommendations. Our data provided supportive evidence for the implementation of the revised WHO guidelines for first-line anti-TB therapy in young children.

Population pharmacokinetic analysis of the active product of dipyrone.

OBJECTIVE: Pharmacokinetics of 4-methyl-amino-antipyrine (MAA), the active metabolite of the nonsteroidal anti-inflammatory agent dipyrone, whose time course correlates to the therapeutic effect of the drug, are studied. STUDY DESIGN AND SETTING: 153 patients hospitalized in the Department of Medicine at the Hadassah University Hospital, Jerusalem, Israel. INTERVENTION: Patients receiving dipyrone for the treatment of fever or pain were asked to participate in the study. Pharmacokinetics and statistical analysis: Using the population approach based on a formerly developed experimental model, the relationships between pharmacokinetic parameters and demographic and physiological covariates are explored. RESULTS: The results of the analysis show considerable variability in pharmacokinetics across the study population, and a significant decrease in clearance with age. CONCLUSION: A population pharmacokinetic analysis of MAA, the active product of dipyrone, reveals that age is a significant predictor of MAA disposition. Covariates that measure hepatic and renal function do not appear to be good predictors of the rate of MAA disposition.

Metabolic disposition of prostaglandin E1 in man.

Metabolism of [17, 18-3H]prostaglandin E1 was investigated in three healthy male volunteers during intravenous infusion. The infusion rate was 5.0 ng/kg per min. Blood samples were obtained before the end of the infusion as well as 5, 10, 20, 40, 90 and 180 min afterwards; urine and feces were collected until 96 and 72 h, respectively, after the experiment. All samples were analyzed for radioactivity. Urine was further chromatographed, including by high-pressure liquid chromatography, and subsequently analyzed by gas chromatography-mass spectrometry. Radioactivity in plasma rapidly declined during the first 10 min after termination of the infusion, and then was eliminated exponentially with a mean half-life of 181 min, probably reflecting slow excretion of one or more metabolite. 12% of the administered radioactivity could be recovered from feces and 88% from urine. From the radioactive material obtained from urine the following metabolites could be identified (each number represents data of one volunteer): 7 alpha-hydroxy-5,11-diketotetranor-prostane-1,16-dioic acid (10.4, 20.4 and 30.1%), 7 alpha-hydroxy-5,11-diketotetranor-prostanoic acid (8.2, 6.9 and 9.3%), 5 alpha, 7 alpha-dihydroxy-11-ketotetranor-prostane-1,16-dioic acid and its delta-lactone (together accounting for 4.1, 2.1 and 3.8%).

Identification of the major metabolite of prostacyclin and 6-ketoprostaglandin F1 alpha in man.

Human volunteers were infused with 3H- and 2H-labeled prostacyclin or 3H-labeled 6-ketoprostaglandin F1 alpha and, in separate experiments, with the unlabeled prostanoids. The urine was purified by different chromatographic steps and finally separated into several fractions by high-performance liquid chromatography. The major fractions contained 20.5 and 23.0% of the eluted readioactivity for the metabolites of prostacyclin and 6-ketoprostaglandin F1 alpha, respectively. The structure of both metabolites was identified by gas-liquid chromatography-mass spectrometry as dinor-6-ketoprostaglandin F1 alpha. It is concluded that the major metabolite of prostacyclin and 6-ketoprostaglandin F1 alpha in man is dinor-6-ketoprostaglandin F1 alpha.

Effect of single doses of cimetidine and ranitidine on the steady-state plasma levels of midazolam.

H2-Receptor antagonists may interfere with the pharmacokinetics of concomitantly administered drugs. Our study was designed to investigate whether cimetidine or ranitidine influence the disposition and sedative effect of midazolam. The effect of single oral doses of 800 mg cimetidine, 300 mg ranitidine, or placebo on the steady-state concentrations of midazolam was examined in a randomized crossover study in eight healthy subjects. A midazolam steady-state concentration was achieved by an intravenous bolus (0.05 mg/kg)-infusion (0.025 mg/kg/hr) technique. Plasma concentrations of midazolam, cimetidine, and ranitidine and the pharmacodynamic response to midazolam (choice reaction time, sedation index) were monitored throughout the 10-hour infusion. Cimetidine significantly increased the mean (+/- SD) steady-state plasma concentration of midazolam from 56.7 +/- 7.8 to 71.3 +/- 19.6 ng/ml (P = 0.004). In contrast, the steady-state midazolam concentration after ranitidine dosing (61.8 +/- 6.8 ng/ml) did not differ significantly from that after placebo. No change in choice reaction time or sedation index was detected after cimetidine or ranitidine dosing. Nevertheless, in contrast to ranitidine, the recently advocated once-daily dosing of cimetidine has a potential for hepatic drug interaction that should be considered before its coadministration with drugs that have a narrow therapeutic index.

Prostacyclin metabolites in human plasma.

The major metabolites of prostacyclin (PGI2) in human plasma have been determined after intravenous infusion of tritium-labeled prostacyclin. Plasma was extracted and chromatographed. On high-pressure liquid chromatography (HPLC), several radioactive peaks could be resolved. The major peak containing 41.6% of the radioactivity had the retention volume of authentic 6-keto-prostaglandin F 1 alpha (6-keto-PGF 1 alpha), the stable in vitro hydrolysis product of prostacyclin. When the material of this peak was derivatized to the methoxime methyl ester trimethylsilyl ether and analyzed by gas chromatography-mass spectrometry, the fragments m/z 508 and 598, which are characteristic of this derivative of 6-keto-PFG 1 alpha were detected. A much smaller peak representing 6.6% of the radioactivity eluted from HPLC with the same retention volume as dinor-6, 15-diketo-13, 14-dihydro-PGF 1 alpha. On gas chromatography-mass spectrometry this material resulted in the fragments m/z 527, 468, 437, and 347, which are characteristic for this prostanoid. Finally, 10.1% of the radioactivity with ions m/z 571m 481, 391, and 354 on mass spectrometric analysis could be identified as dinor-6, 15-diketo-13, 14-dihydro-20-carboxyl-PGF 1 alpha. It is concluded that 6-keto-PFG 1 alpha represents the major breakdown product of prostacyclin in human plasma. In addition, dinor-6, 15-diketo-13, 14-dihydro-PGF 1 alpha and its w-oxidized analog could be identified circulating metabolites.

Single-dose pharmacokinetics of cefpirome in patients with renal impairment.

The pharmacokinetic parameters of cefpirome (HR 810) were examined in 22 patients with different degrees of renal impairment. HPLC was used to analyze samples of blood and urine for cefpirome; and enzymatic assay of creatinine in serum and urine was used to assess kidney function. Creatinine clearance correlated linearly with both total and renal clearance of cefpirome. The loss of kidney function resulted in a decreased renal clearance, whereas the volume of distribution remained the same. This result led to an increase in the terminal half-life of the drug, from 2 hours in healthy subjects to 14 1/2 hours in patients with uremia. This increase also resulted in a prolonged high serum concentration well above the minimum inhibitory concentration. The following dosages are thus recommended: (1) creatinine clearance greater than 50 ml/min: normal daily dose, (2) creatinine clearance from 20 to 50 ml/min: 50% of normal daily dose, and (3) creatinine clearance less than 20 ml/min: 25% of normal daily dose. An initial loading dose of 1 gm, independent of renal function, is advised. Cefpirome was safe and well tolerated.

Single-dose pharmacokinetics of cefpirome in patients receiving hemodialysis and in patients treated by continuous ambulatory peritoneal dialysis.

Cefpirome is eliminated primarily by renal excretion, compelling dosage reduction in kidney failure. We studied the elimination kinetics after intravenous administration of 1 gm cefpirome in patients undergoing hemodialysis (n = 9) and after intravenous (n = 6) or intraperitoneal administration (n = 6) of 1 gm cefpirome in subjects treated by continuous ambulatory peritoneal dialysis (CAPD). Four hours of hemodialysis removed 48% +/- 9% of the drug present in the body at the start of hemodialysis. Consequently, a supplementary dose equal to 50% of the daily dose recommended in end stage renal disease (ESRD) should be administered after each hemodialysis treatment. In patients receiving CAPD, therapeutic levels in both serum and dialysate were reached after intravenous and intraperitoneal administration. The bioavailability after intraperitoneal administration was 84%. After systemic administration, the elimination of cefpirome in the dialysate was negligible. Consequently, systemic dosage of cefpirome in patients receiving CAPD and in patients with ESRD should be identical.

Clinical pharmacokinetics of molsidomine.

Molsidomine is a prodrug for the formation of nitric oxide (NO). Its pharmacokinetics are characterised by rapid absorption and hydrolysis, taking a short time to achieve maximal systemic concentrations of both the parent compound and its active metabolite, SIN-1. The time to peak plasma drug concentration (tmax) is 1 to 2 hours. The bioavailability of the parent compound after oral administration in tablet form is 44 to 59%, but further metabolism to release NO and form polar metabolites is rapid; the half-life (t-1/2) of SIN-1 is 1 to 2 hours. Urinary excretion accounts for more than 90% of the part of the administered dose of molsidomine which is not excreted unchanged. Protein binding of the parent compound is very low (3 to 11%) and its volume of distribution (Vd) corresponds to the range of bodyweight. Single-dose studies (1, 2 and 4 mg) have revealed linear pharmacokinetics, and multiple dose studies in healthy individuals (2 mg 3 times daily for 7 days) and coronary artery disease (CAD) patients (4 mg 4 times daily for 4 weeks) do not show any accumulation of the drug. A study in young and elderly individuals indicated that the first-pass effect is decreased and t-1/2 prolonged with age, resulting in an increased area under the concentration-time curve (AUC) of molsidomine and SIN-1. In patients with liver disease and congestive heart failure similar changes were observed, but much less so in patients with CAD. Clearance was also impaired in patients with liver disease, but the pharmacokinetics of molsidomine were not markedly altered by impaired renal function. In general, due to a large therapeutic dose range, dosage adjustments are not required on the basis of clinical experience. In certain patients a lower starting dose may be recommended, such as in those with impaired liver or kidney function, in congestive heart failure or in the presence of concomitant treatment with other vasoactive compounds. A linear dose-effect relationship is observed with counterclockwise hysteresis, i.e. a greater effect associated with the decrease of plasma concentrations than during their increase, which may be at least partly due to the metabolic delay in the formation of NO from SIN-1. Accordingly, the duration of action of molsidomine is longer than would be expected on the basis of the elimination half-life. The pharmacokinetics of molsidomine support the recommended dosages for use in angina pectoris.

Clinical pharmacokinetics of dipyrone and its metabolites.

The pharmacokinetics of dipyrone are characterised by rapid hydrolysis to the active moiety 4-methyl-amino-antipyrine (MAA), which has 85% bioavailability after oral administration in tablet form, and takes a short time to achieve maximal systemic concentrations (tmax of 1.2 to 2.0 hours). Absolute bioavailability after intramuscular and rectal administration is 87 and 54%, respectively. MAA is further metabolised with a mean elimination half-life (t1/2) of 2.6 to 3.5 hours to 4-formyl-amino-antipyrine (FAA), which is an end-metabolite, and to 4-amino-antipyrine (AA), which is then acetylated to 4-acetyl-amino-antipyrine (AAA) by the polymorphic N-acetyl-transferase (t1/2 of AA is 3.8 hours in rapid acetylators and 5.5 hours in slow acetylators). Urinary excretion of these 4 metabolites accounts for about 60% of the administered dose of dipyrone. Protein binding of the 4 main metabolites is less than 60%. The volume of distribution of MAA is about 1.15 L/kg of lean body mass. All 4 metabolites are excreted into breast milk. A single-dose study (0.75, 1.5 and 3g) and a multiple-dose study (1g 3 times a day for 7 days) revealed nonlinear pharmacokinetics consistent with a shift of MAA metabolism from FAA to AA. Apparent MAA clearance decreased by 22% during multiple administration. MAA clearance was reduced by 33% in the elderly. In patients with cirrhosis of the liver, the apparent clearance of all metabolites is generally reduced. In patients with renal disease, apparent clearance of MAA remains unchanged, whereas elimination of the renally excreted metabolites AAA and FAA is markedly impaired. No clinically important drug interactions have thus far been recognised. Dipyrone does not affect the pharmacodynamic response to alcohol (ethanol), glibenclamide (glyburide), oral anti-coagulants or furosemide (frusemide). The low toxicity of dipyrone and its efficacy support its use in clinical practice, despite some complex aspects of its disposition.

Ofloxacin pharmacokinetics in chronic renal failure and dialysis.

Data on the pharmacokinetics of ofloxacin in chronic renal failure, in patients who were not dialysed or were receiving haemodialysis or continuous ambulatory peritoneal dialysis (CAPD), are reviewed. In addition, a large pool of data obtained in patients with a wide range of renal dysfunction is provided. The good absorption of ofloxacin after oral administration is not influenced by renal failure. Total plasma clearance (CL) is largely dependent on renal elimination of the drug, and renal clearance (CLR) and urinary recovery are reduced in parallel with reductions in renal function. Consequently, the serum half-life progressively increases when creatinine clearance decreases. Although there is wide variation in the published absolute values for the CL and CLR of ofloxacin, all studies show a similar pattern in the pharmacokinetic behaviour of the drug in chronic renal failure. A proposed protocol for ofloxacin dosage adjustment in chronic renal failure is reported which differs slightly but significantly from that recommended by the manufacturer. This new dosage regimen was derived from the pharmacokinetic results after single and multiple oral administration of the drug to patients with chronic renal failure. Since no clinically relevant losses of ofloxacin occur during haemodialysis or continuous ambulatory peritoneal dialysis (CAPD), the same protocol should be followed in these patients as in undialysed patients with terminal chronic renal failure.

A pharmacokinetic study of roxatidine acetate in chronic renal failure.

The pharmacokinetics of a single oral dose of roxatidine acetate 150 mg were studied in 31 patients with varying degrees of chronic renal failure. The patients were divided into 5 groups according to their creatinine clearance (Clcr): controls (Clcr 94.5 +/- 13.9 ml/min; n = 6); mild chronic renal failure (Clcr 47 +/- 6 ml/min; n = 4); moderate chronic renal failure (Clcr 27.3 +/- 3.1 ml/min; n = 4); severe chronic renal failure (Clcr 12.8 +/- 1.4 ml/min; n = 5) and uraemia (Clcr 6.6 +/- 0.6 ml/min; n = 12). Serum and urine samples were analysed with capillary gas chromatography to measure the salt of the desacetyl metabolite of roxatidine acetate (roxatidine). The terminal half-life was 6.02 +/- 0.31 hours in controls and 7.35 +/- 0.57, 9.3 +/- 0.83, 14.6 +/- 3.7 and 18.10 +/- 2.77 hours, respectively, in the 4 other groups, with progressively decreasing creatinine clearance. Maximum serum concentration and time to maximum serum concentration rose from 816 +/- 75 ng/ml and 2.08 +/- 0.22 hours, respectively, in controls to 1364.7 +/- 156 ng/ml and 4.05 +/- 0.47 hours, respectively, in uraemic patients. Relative total clearance progressively decreased with decreasing glomerular filtration rate (GFR) [from 353.6 +/- 26 ml/min in controls to 90.31 +/- 12.2 ml/min in patients with uraemia]. Renal clearance decreased from a control of 243.9 +/- 56 ml/min to 12.32 +/- 0.18 ml/min in uraemic patients. A linear correlation between creatinine clearance and both relative total clearance and renal drug clearance was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway pharmacology of the potassium channel opener, HOE 234, in guinea pigs: in vitro and in vivo studies.

The smooth muscle relaxant effects of the novel potassium channel opener, HOE 234, were investigated in guinea pig airways and compared with those of lemakalim (BRL 38227). Both agents evoked concentration-related reduction in spontaneous tracheal tone or in the tone induced by histamine, prostaglandin E2 or carbachol. HOE 234 was more potent, particularly against carbachol, and was considerably longer acting than lemakalim in a wash-out experiment. On testing for preventive efficacy against histamine-induced bronchoconstriction in anaesthetized animals a dose-related decrease of pulmonary resistance (RL) was observed. HOE 234 given either intravenously (i.v.) or by inhalation was longer acting and 3 and 6 times more potent than lemakalim. Administration of 30 micrograms/kg i.v. HOE 234 during continuous bronchoconstriction maintained by infusion of histamine decreased RL for more than 20 min whereas the effect of 100 micrograms/kg i.v. lemakalin disappeared within 4 min. These results show that HOE 234 is effective against contractile response induced by asthma mediators in guinea pig airways and compares favourably with lemakalim. Moreover it acts on acute existing bronchospasm and therefore has the potential to act against asthma attacks.

Mechanism of vasopressin-induced platelet aggregation.

The mechanism of aggregation induced by arginine vasopressin (AVP) was studied in human platelet rich plasma. AVP--over the range of 1.8-113.6 mU/ml--caused a dose-dependent aggregation with a concomitant stimulation of thromboxane B2 (TXB2) formation. d(CH2)5Tyr (Me)AVP did not by itself affect platelet aggregation or TXB2 release, but completely inhibited the action of AVP. DDAVP up to the concentration of 280 pM/ml had no effect on aggregation. Pretreatment of platelets with verapamil, trifluoroperazine or methylimidazole, a thromboxane synthetase blocker, prevented AVP-induced aggregation and TXB2 release. Neither phenidone in lower concentration nor nordihydroguaiaretic acid inhibited the ability of AVP to induce aggregation and TXB2 release. These results are consistent with the hypothesis that human platelets possess AVP receptor of the calcium-dependent vasopressor (V1) subtype and suggest that AVP-induced platelet aggregation is mediated via thromboxane release.

Absence of interaction between ofloxacin and phenprocoumon.

The effect of ofloxacin on steady-state phenprocoumon pharmacodynamics was investigated in 7 healthy male volunteers taking daily sub-therapeutic doses of phenprocoumon. Ofloxacin 200 mg once daily for 7 days did not alter the anti-coagulant response (Quick values) to phenprocoumon after a stabilization phase of 2 weeks. Mean Quick values during the steady-state phase before and during ofloxacin administration were 54% and 52%, respectively. In vitro studies with concentrations of 0 to 100 mg ofloxacin/1 added to plasma also failed to show any interaction. The results indicate, therefore, that ofloxacin does not interfere with vitamin K-dependent coagulation cascade, as seen after other antibiotics.

Phase I studies: what to measure?

Drug law require the assessment of quality, safety and efficacy of new compounds. In this context, phase I studies are performed in order to investigate their tolerability, pharmacodynamic effects and pharmacokinetics. For the assessment of safety aspects, standard clinical (eg blood pressure, heart rate, body temperature, ECG), laboratory data (eg checklist recommended by local clinical chemistry societies) and subjective rating scales (eg open or structured questionnaires) are the main parameters. Additional investigations may be included according to the results obtained in pharmacological and toxicological studies. The selection of appropriate measuring times is crucial. The maximum pharmacological effects in many cases are seen at the time of peak serum concentration, whereas in other cases they may be a delay (eg effect on coagulation factors, toxic granulocytopenia). For the assessment of the pharmacodynamic effects of a new drug, standardized procedures should be used which predict its therapeutic effect in patients. The main purposes of pharmacodynamic studies in healthy volunteers are: proof of efficacy and mechanism of action in man, dose finding, search for possible adverse events, for additional therapeutically relevant mechanisms or pharmacodynamic interactions. For all these studies, it is crucial to select the appropriate variables, the appropriate validated and non-invasive method and the appropriate time points.

Pulp capping of carious exposures: treatment outcome after 5 and 10 years: a retrospective study.

One hundred twenty-three pulp cappings had been performed by students in 1984 to 1987 (= 10-yr group) or in 1990 to 1992 (= 5-yr group) and were followed up in 1997. Teeth were checked for sensitivity (CO2/electrical pulp testing), percussion, and palpation; radiographs were taken to assess periapical status. In addition several other factors were determined that might have an influence on the success or failure rates, such as base material, type of restoration, site of exposure, etc. Results showed 44.5% failures (18.5% questionable and 37% successful cases) in the 5-yr group and 79.7% failing, 7.3% questionable, and 13% successful cases in the 10-yr group. As a factor of influence, the placement of a definitive restoration within the first 2 days after pulp exposure was found to contribute significantly to the survival rate of these teeth.