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The influence of pH on the acute toxicity of NSAIDs (ketoprofen, diclofenac, naproxen and ibuprofen) towards Daphnia magna (water flea)

Li, Jiakai (2012) BIOM14 20121
Degree Projects in Biology
Abstract
Abstract

Ketoprofen, naproxen, diclofenac, and ibuprofen are four widelyused anti-inflammatory drugsthat areproduced in several kilotons each year.They end up in natural water recipients which couldvary inpH from around 6.0 to 9.0. Bearing in mind that most of thesepharmaceuticals are weak acids and therefore dissociates in different degree depending on surroundingpH and the chemical’s pKa, we carried out an acute48h toxicitystudyon Daphnia magnaat threeenvironmental pHs--6.0, 7.5 and 9.0. We hypothesize that low pH will increase the proportion of the neutral form of these four non-steroidalanti-inflammatorydrugs (NSAIDs), and thus we can expect ahighertoxicity at low pH. Compare toEC50sat pH 9.0, results showeda statistically... (More)
Abstract

Ketoprofen, naproxen, diclofenac, and ibuprofen are four widelyused anti-inflammatory drugsthat areproduced in several kilotons each year.They end up in natural water recipients which couldvary inpH from around 6.0 to 9.0. Bearing in mind that most of thesepharmaceuticals are weak acids and therefore dissociates in different degree depending on surroundingpH and the chemical’s pKa, we carried out an acute48h toxicitystudyon Daphnia magnaat threeenvironmental pHs--6.0, 7.5 and 9.0. We hypothesize that low pH will increase the proportion of the neutral form of these four non-steroidalanti-inflammatorydrugs (NSAIDs), and thus we can expect ahighertoxicity at low pH. Compare toEC50sat pH 9.0, results showeda statistically significant decrease ofthe EC50s ofketoprofen and naproxen at pH 6.0. However, we did not find any statistical difference forEC50s ofdiclofenac and ibuprofen, whereaswe do observe the sametrend withincreasing EC50sat higher pH.This studysupports the hypothesis that there is a positiverelationship between the neutral form of these four chemicals and their toxicity, which means that they can be more toxic when present in natural aquaticenvironmentwithlow pH.

Popular science summary:

The influence of pH on the acute toxicity of NSAIDs (ketoprofen, diclofenac, naproxen, and ibuprofen) towards Daphnia magna (water flea)

Will the toxicity of NSAIDs (weak acids), a popular group of as anti-inflammatory pharmaceuticals, be the same when they present in natural water environments with different pH value? Since the pH will affect the proportion of the neutral form of these weak acids, the answer might be negative. However, most studies toward the toxicity of NSAIDs (e.g. ketoprofen, naproxen, diclofenac, and ibuprofen) are carried out under a single pH value. Therefore we carried out this study in order to investigate to what extent the pH fluctuation in natural aquatic environments might affect the toxicity of the above four mentioned NSAIDs.

By using pH buffers to maintain a relatively stable pH, we carried out several 48h acute toxicity tests, with immobilization as endpoint, toward Daphnia magna at three pH levels –6.0, 7.5, and 9.0 to measure EC50s (50% effect concentrations) for the four NSAIDs mentioned above. Then we compared: 1) the regression coefficient of different EC50s’ to sort out any direct effects of pH, and 2) different EC50-values at de different pHs. By combining these two comparisons, we were able to study differences in: 1) sensitivity of Daphnia magna toward increased concentration of NSAIDs, and 2) toxic effect of NSAIDs at three pHs.

Results showed that there is a statistically significant difference of 1) the regression coefficient for ketoprofen at different pH levels, (from 2.34±1 to 0.57±0.28 when the pH was changed from 6.0 to 9.0), as well as 2) the EC50-values of ketoprofen and naproxen at pH 6.0 and 9.0 (for ketoprofen from 1.48-1.82 mg/l at pH 6.0 to 1.97-2.89 mg/l at pH 9.0 and naproxen from 0.67-1.22 mg/l at pH 6.0 to 1.53-2.47 mg/l at pH 9.0), and the same trend was seen for diclofenac and ibuprofen. Therefore we have reasons to believe that: 1) Daphnia magna might be more sensitive to ketoprofen concentration increase at low pH but as we did not see the same thing for the other NSAIDs we feel confident to dismiss any direct pH effect, and 2) NSAIDs are more toxic when present in an aquatic environment with low pH even if only a small percentage of the chemical is in the neutral state. For the reason that ketoprofen and naproxen are both weak acids, this study supports the hypothesis that weak acids will be more toxic at low pH, and further study about the predicted no effect concentration of NSAIDs still needed.

Advisor: Olof Berglund; Marja Boström
Master´s Degree Project 30 credits in Ecotoxicology, 2012
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Li, Jiakai
supervisor
organization
course
BIOM14 20121
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
3731767
date added to LUP
2013-04-26 15:27:36
date last changed
2013-04-26 15:27:36
@misc{3731767,
  abstract     = {Abstract

Ketoprofen, naproxen, diclofenac, and ibuprofen are four widelyused anti-inflammatory drugsthat areproduced in several kilotons each year.They end up in natural water recipients which couldvary inpH from around 6.0 to 9.0. Bearing in mind that most of thesepharmaceuticals are weak acids and therefore dissociates in different degree depending on surroundingpH and the chemical’s pKa, we carried out an acute48h toxicitystudyon Daphnia magnaat threeenvironmental pHs--6.0, 7.5 and 9.0. We hypothesize that low pH will increase the proportion of the neutral form of these four non-steroidalanti-inflammatorydrugs (NSAIDs), and thus we can expect ahighertoxicity at low pH. Compare toEC50sat pH 9.0, results showeda statistically significant decrease ofthe EC50s ofketoprofen and naproxen at pH 6.0. However, we did not find any statistical difference forEC50s ofdiclofenac and ibuprofen, whereaswe do observe the sametrend withincreasing EC50sat higher pH.This studysupports the hypothesis that there is a positiverelationship between the neutral form of these four chemicals and their toxicity, which means that they can be more toxic when present in natural aquaticenvironmentwithlow pH.

Popular science summary:

The influence of pH on the acute toxicity of NSAIDs (ketoprofen, diclofenac, naproxen, and ibuprofen) towards Daphnia magna (water flea) 

Will the toxicity of NSAIDs (weak acids), a popular group of as anti-inflammatory pharmaceuticals, be the same when they present in natural water environments with different pH value? Since the pH will affect the proportion of the neutral form of these weak acids, the answer might be negative. However, most studies toward the toxicity of NSAIDs (e.g. ketoprofen, naproxen, diclofenac, and ibuprofen) are carried out under a single pH value. Therefore we carried out this study in order to investigate to what extent the pH fluctuation in natural aquatic environments might affect the toxicity of the above four mentioned NSAIDs. 

By using pH buffers to maintain a relatively stable pH, we carried out several 48h acute toxicity tests, with immobilization as endpoint, toward Daphnia magna at three pH levels –6.0, 7.5, and 9.0 to measure EC50s (50% effect concentrations) for the four NSAIDs mentioned above. Then we compared: 1) the regression coefficient of different EC50s’ to sort out any direct effects of pH, and 2) different EC50-values at de different pHs. By combining these two comparisons, we were able to study differences in: 1) sensitivity of Daphnia magna toward increased concentration of NSAIDs, and 2) toxic effect of NSAIDs at three pHs. 

Results showed that there is a statistically significant difference of 1) the regression coefficient for ketoprofen at different pH levels, (from 2.34±1 to 0.57±0.28 when the pH was changed from 6.0 to 9.0), as well as 2) the EC50-values of ketoprofen and naproxen at pH 6.0 and 9.0 (for ketoprofen from 1.48-1.82 mg/l at pH 6.0 to 1.97-2.89 mg/l at pH 9.0 and naproxen from 0.67-1.22 mg/l at pH 6.0 to 1.53-2.47 mg/l at pH 9.0), and the same trend was seen for diclofenac and ibuprofen. Therefore we have reasons to believe that: 1) Daphnia magna might be more sensitive to ketoprofen concentration increase at low pH but as we did not see the same thing for the other NSAIDs we feel confident to dismiss any direct pH effect, and 2) NSAIDs are more toxic when present in an aquatic environment with low pH even if only a small percentage of the chemical is in the neutral state. For the reason that ketoprofen and naproxen are both weak acids, this study supports the hypothesis that weak acids will be more toxic at low pH, and further study about the predicted no effect concentration of NSAIDs still needed. 

Advisor: Olof Berglund; Marja Boström 
Master´s Degree Project 30 credits in Ecotoxicology, 2012 
Department of Biology, Lund University},
  author       = {Li, Jiakai},
  language     = {eng},
  note         = {Student Paper},
  title        = {The influence of pH on the acute toxicity of NSAIDs (ketoprofen, diclofenac, naproxen and ibuprofen) towards Daphnia magna (water flea)},
  year         = {2012},
}