Case Studies in Toxicology: When Doing More for the Sake of Better Health Goes Wrong

Case

A 62-year-old man with a history of hypercholesterolemia and HIV infection presented to the ED for evaluation of diffuse myalgia and tea-colored urine. His medication history included lopinavir/ritonavir (Kaletra) and simvastatin. A week prior to presentation, the patient’s primary care physician had instructed him to increase his daily dose of simvastatin from 40 mg to 80 mg. The patient stated that he had taken simvastatin 80 mg daily for approximately 5 days and then, 2 days prior to presentation, had independently further increased the dose to 160 mg daily.

In the ED, the patient reported feeling fatigued. His initial vital signs were: blood pressure, 129/86 mm Hg; heart rate, 93 beats/minute; respiratory rate, 17 breaths/minute; and temperature, 98.5˚F. Oxygen saturation was 98% on room air. His physical examination was unremarkable. Initial laboratory testing revealed the following: creatine kinase (CK) 350,000 U/L; blood urea nitrogen, 27 mg/dL; creatinine, 0.7 mg/dL; aspartate aminotransferase (AST), 2,950 U/L; and alanine aminotransferase (ALT), 1,305 U/L.

What can cause tea-colored/cola-colored urine and myalgia?

Numerous medications can result in dark-colored urine. These include antimalarial drugs such as chloroquine and primaquine; antibiotics such as metronidazole or nitrofurantoin; and the muscle relaxant methocarbamol. Myalgia and tea-colored urine are the hallmarks of rhabdomyolysis. Rhabdomyolysis involves the destruction of myocytes, which can occur as a result of a long list of processes, including crush injuries, poor oxygenation or perfusion, hypermetabolic states, and direct (or indirect) toxin-mediated myocyte damage.¹ The list of toxic substances that can cause rhabdomyolysis is extensive, and statins are one of the most common drug-induced causes (Table).

Simvastatin is one of seven currently available 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (ie, statins) that are commonly used to treat hypercholesterolemia. Because simvastatin is lipophilic, it can more readily cross cell membranes than nonlipophilic statins such as pravastatin. Simvastatin, therefore, has a propensity to disrupt the cellular integrity of myocytes and hepatocytes.What is the likely cause of this patient’s rhabdomyolysis?

At doses greater than 40 mg daily, simvastatin is associated with myalgia, myositis, and rhabdomyolysis. In December 2011, the US Food and Drug Administration (FDA) released a drug safety announcement recommending the originally approved maximum daily dose of simvastatin 80 mg be limited to patients who have already tolerated that dose for at least 12 months without evidence of muscular injury. The FDA further recommended no new patients be escalated to this dose. According to the FDA, patients taking 80 mg of simvastatin daily are also at increased risk of myopathy. 

The metabolism of simvastatin, in addition to increased dosage of the drug, contributes to its potential for adverse effects. Of the seven available statins, only atorvastatin, lovastatin, and simvastatin are metabolized by the cytochrome P450 3A4 (CYP3A4). Lovastatin and simvastatin appear to have the highest potential for drug-drug interactions when coadministered with drugs that inhibit this enzyme (eg, ritonavir).² The resulting elevation in blood concentration of simvastatin increases the risk of rhabdomyolysis. Other nonlipophilic statins, such as pravastatin, which are mostly eliminated unchanged in the urine and bile, would be preferable for patients taking CYP3A4 inhibitors.

How should patients with rhabdomyolysis be monitored?

Statins interfere with the myocyte’s ability to produce adenosine triphosphate, most likely by depleting coenzyme Q—one of the complexes found in the electron transport chain of the mitochondria. Under conditions of a high-energy requirement, myocytes incapable of producing sufficient energy ultimately fail and lyse, releasing cellular contents such as CK and myoglobin.¹ The serum CK activity serves as a marker of muscle injury and should be monitored closely in patients with rhabdomyolysis. Although values above 5,000 U/L has been associated with renal injury,⁴ in healthy patients with access to hydration, renal injury is relatively uncommon with CK activities less than 50,000 U/L. Even though the prediction of renal failure is difficult, a validated nephrotoxicity prediction instrument using the patient’s age, gender, and initial laboratory data (serum creatinine, calcium, CK, phosphate, and bicarbonate) is available.⁵

Although the association between rhabdomyolysis and acute renal injury is well established, the mechanism remains unclear. Myoglobin from skeletal myocytes passes through the glomerulus without causing damage and is reabsorbed in the proximal renal tubular cell. Iron is subsequently released from the porphyrin ring and, in large concentrations, exceeds the binding capacity of the tissue ferritin. Because it is a transition metal, the free iron ion participates in oxidant stress reactions causing direct injury to the renal tubular cells.⁶ Furthermore, myoglobin also combines with renal tubular proteins, a process enhanced by an environment with lower pH, to form casts and cause renal tubular obstruction.

Patients with rhabdomyolysis may also be at risk for aminotransferase elevation, as occurred in the patient presented here. This elevation is most likely due to myocyte injury. In addition, potassium release due to myocyte destruction may cause life-threatening hyperkalemia, and phosphate liberation from these myocytes may cause hypocalcemia. Laboratory monitoring along with an electrocardiogram should be performed as required.

What is the treatment for rhabdomyolysis?

No adequate randomized controlled trials exist to guide the treatment of patients with rhabdomyolysis. As a result, recommendations for management come from retrospective observational studies, animal studies, case reports, and expert opinion.⁷

Once airway, breathing, and circulation have been addressed, patients with statin-induced rhabdomyolysis should be immediately treated with intravenous (IV) fluids to maintain renal perfusion, which helps to limit acute renal injury. Normal saline appears to be the most recommended fluid type, with a goal of maintaining a urine output of approximately 3 to 5 mL/kg/h.^4,7

Some recommendations include the use of a sodium bicarbonate infusion to raise the urine pH, which may help limit the formation of renal casts from myoglobin. The data to support the benefit of sodium bicarbonate, however, is weak.³ A 2013 systematic review indicated that sodium bicarbonate should only be used to treat severe metabolic acidosis in patients with rhabdomyolysis.⁴

In addition to sodium bicarbonate, the use of diuretics is also discouraged by current recommendations. In patients with refractory electrolyte abnormalities or renal failure, hemodialysis may be required. Before disposition of a patient, his or her medication list should be reconciled to reflect statin discontinuation. 

Case Conclusion

The patient received IV normal saline to maintain his urine output at 2 to 3 cc/kg/h. His repeat creatinine was 0.8 mg/dL and remained stable on repeat testing. His CK and AST concentrations trended down during his hospitalization. On hospital day 4, laboratory values were CK, less than 10,000 U/L; AST, 56 U/L; and ALT, 23 U/L. He had normal serum potassium levels and no dysrhythmia on electrocardiogram. His symptoms resolved on hospital day 2, and he was discharged on hospital day 4 with instructions to discontinue simvastatin.

Dr Fernandez is a senior toxicology fellow, department of emergency medicine, New York University School of Medicine. Dr Nelson, editor of “Case Studies in Toxicology,” is a professor in the department of emergency medicine and director of the medical toxicology fellowship program at the New York University School of Medicine and the New York City Poison Control Center. He is also associate editor, toxicology, of the EMERGENCY MEDICINE editorial board.

Case

A 62-year-old man with a history of hypercholesterolemia and HIV infection presented to the ED for evaluation of diffuse myalgia and tea-colored urine. His medication history included lopinavir/ritonavir (Kaletra) and simvastatin. A week prior to presentation, the patient’s primary care physician had instructed him to increase his daily dose of simvastatin from 40 mg to 80 mg. The patient stated that he had taken simvastatin 80 mg daily for approximately 5 days and then, 2 days prior to presentation, had independently further increased the dose to 160 mg daily.

In the ED, the patient reported feeling fatigued. His initial vital signs were: blood pressure, 129/86 mm Hg; heart rate, 93 beats/minute; respiratory rate, 17 breaths/minute; and temperature, 98.5˚F. Oxygen saturation was 98% on room air. His physical examination was unremarkable. Initial laboratory testing revealed the following: creatine kinase (CK) 350,000 U/L; blood urea nitrogen, 27 mg/dL; creatinine, 0.7 mg/dL; aspartate aminotransferase (AST), 2,950 U/L; and alanine aminotransferase (ALT), 1,305 U/L.

What can cause tea-colored/cola-colored urine and myalgia?

Numerous medications can result in dark-colored urine. These include antimalarial drugs such as chloroquine and primaquine; antibiotics such as metronidazole or nitrofurantoin; and the muscle relaxant methocarbamol. Myalgia and tea-colored urine are the hallmarks of rhabdomyolysis. Rhabdomyolysis involves the destruction of myocytes, which can occur as a result of a long list of processes, including crush injuries, poor oxygenation or perfusion, hypermetabolic states, and direct (or indirect) toxin-mediated myocyte damage.¹ The list of toxic substances that can cause rhabdomyolysis is extensive, and statins are one of the most common drug-induced causes (Table).

Simvastatin is one of seven currently available 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (ie, statins) that are commonly used to treat hypercholesterolemia. Because simvastatin is lipophilic, it can more readily cross cell membranes than nonlipophilic statins such as pravastatin. Simvastatin, therefore, has a propensity to disrupt the cellular integrity of myocytes and hepatocytes.What is the likely cause of this patient’s rhabdomyolysis?

At doses greater than 40 mg daily, simvastatin is associated with myalgia, myositis, and rhabdomyolysis. In December 2011, the US Food and Drug Administration (FDA) released a drug safety announcement recommending the originally approved maximum daily dose of simvastatin 80 mg be limited to patients who have already tolerated that dose for at least 12 months without evidence of muscular injury. The FDA further recommended no new patients be escalated to this dose. According to the FDA, patients taking 80 mg of simvastatin daily are also at increased risk of myopathy. 

The metabolism of simvastatin, in addition to increased dosage of the drug, contributes to its potential for adverse effects. Of the seven available statins, only atorvastatin, lovastatin, and simvastatin are metabolized by the cytochrome P450 3A4 (CYP3A4). Lovastatin and simvastatin appear to have the highest potential for drug-drug interactions when coadministered with drugs that inhibit this enzyme (eg, ritonavir).² The resulting elevation in blood concentration of simvastatin increases the risk of rhabdomyolysis. Other nonlipophilic statins, such as pravastatin, which are mostly eliminated unchanged in the urine and bile, would be preferable for patients taking CYP3A4 inhibitors.

How should patients with rhabdomyolysis be monitored?

Statins interfere with the myocyte’s ability to produce adenosine triphosphate, most likely by depleting coenzyme Q—one of the complexes found in the electron transport chain of the mitochondria. Under conditions of a high-energy requirement, myocytes incapable of producing sufficient energy ultimately fail and lyse, releasing cellular contents such as CK and myoglobin.¹ The serum CK activity serves as a marker of muscle injury and should be monitored closely in patients with rhabdomyolysis. Although values above 5,000 U/L has been associated with renal injury,⁴ in healthy patients with access to hydration, renal injury is relatively uncommon with CK activities less than 50,000 U/L. Even though the prediction of renal failure is difficult, a validated nephrotoxicity prediction instrument using the patient’s age, gender, and initial laboratory data (serum creatinine, calcium, CK, phosphate, and bicarbonate) is available.⁵

Although the association between rhabdomyolysis and acute renal injury is well established, the mechanism remains unclear. Myoglobin from skeletal myocytes passes through the glomerulus without causing damage and is reabsorbed in the proximal renal tubular cell. Iron is subsequently released from the porphyrin ring and, in large concentrations, exceeds the binding capacity of the tissue ferritin. Because it is a transition metal, the free iron ion participates in oxidant stress reactions causing direct injury to the renal tubular cells.⁶ Furthermore, myoglobin also combines with renal tubular proteins, a process enhanced by an environment with lower pH, to form casts and cause renal tubular obstruction.

Patients with rhabdomyolysis may also be at risk for aminotransferase elevation, as occurred in the patient presented here. This elevation is most likely due to myocyte injury. In addition, potassium release due to myocyte destruction may cause life-threatening hyperkalemia, and phosphate liberation from these myocytes may cause hypocalcemia. Laboratory monitoring along with an electrocardiogram should be performed as required.

What is the treatment for rhabdomyolysis?

No adequate randomized controlled trials exist to guide the treatment of patients with rhabdomyolysis. As a result, recommendations for management come from retrospective observational studies, animal studies, case reports, and expert opinion.⁷

Once airway, breathing, and circulation have been addressed, patients with statin-induced rhabdomyolysis should be immediately treated with intravenous (IV) fluids to maintain renal perfusion, which helps to limit acute renal injury. Normal saline appears to be the most recommended fluid type, with a goal of maintaining a urine output of approximately 3 to 5 mL/kg/h.^4,7

Some recommendations include the use of a sodium bicarbonate infusion to raise the urine pH, which may help limit the formation of renal casts from myoglobin. The data to support the benefit of sodium bicarbonate, however, is weak.³ A 2013 systematic review indicated that sodium bicarbonate should only be used to treat severe metabolic acidosis in patients with rhabdomyolysis.⁴

In addition to sodium bicarbonate, the use of diuretics is also discouraged by current recommendations. In patients with refractory electrolyte abnormalities or renal failure, hemodialysis may be required. Before disposition of a patient, his or her medication list should be reconciled to reflect statin discontinuation. 

Case Conclusion

The patient received IV normal saline to maintain his urine output at 2 to 3 cc/kg/h. His repeat creatinine was 0.8 mg/dL and remained stable on repeat testing. His CK and AST concentrations trended down during his hospitalization. On hospital day 4, laboratory values were CK, less than 10,000 U/L; AST, 56 U/L; and ALT, 23 U/L. He had normal serum potassium levels and no dysrhythmia on electrocardiogram. His symptoms resolved on hospital day 2, and he was discharged on hospital day 4 with instructions to discontinue simvastatin.

Dr Fernandez is a senior toxicology fellow, department of emergency medicine, New York University School of Medicine. Dr Nelson, editor of “Case Studies in Toxicology,” is a professor in the department of emergency medicine and director of the medical toxicology fellowship program at the New York University School of Medicine and the New York City Poison Control Center. He is also associate editor, toxicology, of the EMERGENCY MEDICINE editorial board.

Case

A 62-year-old man with a history of hypercholesterolemia and HIV infection presented to the ED for evaluation of diffuse myalgia and tea-colored urine. His medication history included lopinavir/ritonavir (Kaletra) and simvastatin. A week prior to presentation, the patient’s primary care physician had instructed him to increase his daily dose of simvastatin from 40 mg to 80 mg. The patient stated that he had taken simvastatin 80 mg daily for approximately 5 days and then, 2 days prior to presentation, had independently further increased the dose to 160 mg daily.

In the ED, the patient reported feeling fatigued. His initial vital signs were: blood pressure, 129/86 mm Hg; heart rate, 93 beats/minute; respiratory rate, 17 breaths/minute; and temperature, 98.5˚F. Oxygen saturation was 98% on room air. His physical examination was unremarkable. Initial laboratory testing revealed the following: creatine kinase (CK) 350,000 U/L; blood urea nitrogen, 27 mg/dL; creatinine, 0.7 mg/dL; aspartate aminotransferase (AST), 2,950 U/L; and alanine aminotransferase (ALT), 1,305 U/L.

What can cause tea-colored/cola-colored urine and myalgia?

Numerous medications can result in dark-colored urine. These include antimalarial drugs such as chloroquine and primaquine; antibiotics such as metronidazole or nitrofurantoin; and the muscle relaxant methocarbamol. Myalgia and tea-colored urine are the hallmarks of rhabdomyolysis. Rhabdomyolysis involves the destruction of myocytes, which can occur as a result of a long list of processes, including crush injuries, poor oxygenation or perfusion, hypermetabolic states, and direct (or indirect) toxin-mediated myocyte damage.¹ The list of toxic substances that can cause rhabdomyolysis is extensive, and statins are one of the most common drug-induced causes (Table).

Simvastatin is one of seven currently available 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (ie, statins) that are commonly used to treat hypercholesterolemia. Because simvastatin is lipophilic, it can more readily cross cell membranes than nonlipophilic statins such as pravastatin. Simvastatin, therefore, has a propensity to disrupt the cellular integrity of myocytes and hepatocytes.What is the likely cause of this patient’s rhabdomyolysis?

At doses greater than 40 mg daily, simvastatin is associated with myalgia, myositis, and rhabdomyolysis. In December 2011, the US Food and Drug Administration (FDA) released a drug safety announcement recommending the originally approved maximum daily dose of simvastatin 80 mg be limited to patients who have already tolerated that dose for at least 12 months without evidence of muscular injury. The FDA further recommended no new patients be escalated to this dose. According to the FDA, patients taking 80 mg of simvastatin daily are also at increased risk of myopathy. 

The metabolism of simvastatin, in addition to increased dosage of the drug, contributes to its potential for adverse effects. Of the seven available statins, only atorvastatin, lovastatin, and simvastatin are metabolized by the cytochrome P450 3A4 (CYP3A4). Lovastatin and simvastatin appear to have the highest potential for drug-drug interactions when coadministered with drugs that inhibit this enzyme (eg, ritonavir).² The resulting elevation in blood concentration of simvastatin increases the risk of rhabdomyolysis. Other nonlipophilic statins, such as pravastatin, which are mostly eliminated unchanged in the urine and bile, would be preferable for patients taking CYP3A4 inhibitors.

How should patients with rhabdomyolysis be monitored?

Statins interfere with the myocyte’s ability to produce adenosine triphosphate, most likely by depleting coenzyme Q—one of the complexes found in the electron transport chain of the mitochondria. Under conditions of a high-energy requirement, myocytes incapable of producing sufficient energy ultimately fail and lyse, releasing cellular contents such as CK and myoglobin.¹ The serum CK activity serves as a marker of muscle injury and should be monitored closely in patients with rhabdomyolysis. Although values above 5,000 U/L has been associated with renal injury,⁴ in healthy patients with access to hydration, renal injury is relatively uncommon with CK activities less than 50,000 U/L. Even though the prediction of renal failure is difficult, a validated nephrotoxicity prediction instrument using the patient’s age, gender, and initial laboratory data (serum creatinine, calcium, CK, phosphate, and bicarbonate) is available.⁵

Although the association between rhabdomyolysis and acute renal injury is well established, the mechanism remains unclear. Myoglobin from skeletal myocytes passes through the glomerulus without causing damage and is reabsorbed in the proximal renal tubular cell. Iron is subsequently released from the porphyrin ring and, in large concentrations, exceeds the binding capacity of the tissue ferritin. Because it is a transition metal, the free iron ion participates in oxidant stress reactions causing direct injury to the renal tubular cells.⁶ Furthermore, myoglobin also combines with renal tubular proteins, a process enhanced by an environment with lower pH, to form casts and cause renal tubular obstruction.

Patients with rhabdomyolysis may also be at risk for aminotransferase elevation, as occurred in the patient presented here. This elevation is most likely due to myocyte injury. In addition, potassium release due to myocyte destruction may cause life-threatening hyperkalemia, and phosphate liberation from these myocytes may cause hypocalcemia. Laboratory monitoring along with an electrocardiogram should be performed as required.

What is the treatment for rhabdomyolysis?

No adequate randomized controlled trials exist to guide the treatment of patients with rhabdomyolysis. As a result, recommendations for management come from retrospective observational studies, animal studies, case reports, and expert opinion.⁷

Once airway, breathing, and circulation have been addressed, patients with statin-induced rhabdomyolysis should be immediately treated with intravenous (IV) fluids to maintain renal perfusion, which helps to limit acute renal injury. Normal saline appears to be the most recommended fluid type, with a goal of maintaining a urine output of approximately 3 to 5 mL/kg/h.^4,7

Some recommendations include the use of a sodium bicarbonate infusion to raise the urine pH, which may help limit the formation of renal casts from myoglobin. The data to support the benefit of sodium bicarbonate, however, is weak.³ A 2013 systematic review indicated that sodium bicarbonate should only be used to treat severe metabolic acidosis in patients with rhabdomyolysis.⁴

In addition to sodium bicarbonate, the use of diuretics is also discouraged by current recommendations. In patients with refractory electrolyte abnormalities or renal failure, hemodialysis may be required. Before disposition of a patient, his or her medication list should be reconciled to reflect statin discontinuation. 

Case Conclusion

The patient received IV normal saline to maintain his urine output at 2 to 3 cc/kg/h. His repeat creatinine was 0.8 mg/dL and remained stable on repeat testing. His CK and AST concentrations trended down during his hospitalization. On hospital day 4, laboratory values were CK, less than 10,000 U/L; AST, 56 U/L; and ALT, 23 U/L. He had normal serum potassium levels and no dysrhythmia on electrocardiogram. His symptoms resolved on hospital day 2, and he was discharged on hospital day 4 with instructions to discontinue simvastatin.

Dr Fernandez is a senior toxicology fellow, department of emergency medicine, New York University School of Medicine. Dr Nelson, editor of “Case Studies in Toxicology,” is a professor in the department of emergency medicine and director of the medical toxicology fellowship program at the New York University School of Medicine and the New York City Poison Control Center. He is also associate editor, toxicology, of the EMERGENCY MEDICINE editorial board.