To the Editor,
Baclofen (4-beta-chlorophenyl-gamma-aminobutyric acid) is a muscle relaxant, used as an antispasmodic in diseases such as multiple sclerosis, medullary trauma and hiccups1,2.
It is mainly excreted through the kidneys (69%-85%) and has a 2 to 6 hr. half life in healthy people. There is a high risk of neurotoxicity in patients with renal failure, especially if administered with <30ml/min glomerular filtration rate, causing episodes of unconsciousness3,4.
Baclofen intoxication in dialysis patients is rare, with very diverse forms of clinical presentation5-9.
We present the clinical case of a patient with baclofen-induced encephalopathy, with atypical clinical evolution; symptoms did not improve with haemodialysis and the patient went into complete remission following the drug’s discontinuation.
CASE DESCRIPTION
We present a 31-year-old patient with traumatic spinal injury at 20 and a history of repeated urinary infections related to neurogenic bladder (self-catheterisation) and episodes of urinary obstruction. In 2009 he was referred to the nephrology department due to stage 2 chronic kidney disease, with nephrotic-range proteinuria (1.3mg/dl creatinine, 20g/24h proteinuria). The patient refused renal biopsy and in the same year, he stopped attending nephrology consultations.
In January 2012 he started experiencing episodes of deteriorating levels of consciousness. Cranial computerised tomography and lumbar puncture were performed, both with normal results. Electroencephalogram showed diffuse slowing. At that time, creatinine was 3.3mg/dl. The clinical profile was suggested as secondary to urinary infection.
The same symptoms repeated in April 2012, accompanied by spatial and time disorientation. He presented a new episode in the same month, but this time with behavioural change (infantilism, nervousness, aggressiveness). Cerebral MRI was unremarkable. Following this episode, treatment with clonazepam was started.
In May 2012, due to end-stage renal failure analysis results and symptoms, haemodialysis was started using a temporary catheter in the right jugular vein.
Approximately once a month, in the first two hours after starting dialysis, the patient experienced episodes of reduced levels of consciousness and, at times, psychomotor agitation.
The patient was evaluated in November 2012 by the Neurology and Psychiatry department, with no relevant findings. They diagnosed the condition as secondary to hypoxic metabolic encephalopathy.
Despite presenting correct KT and Kt/V, we increased the number of dialysis sessions to 4/week, without clinical improvement.
In January 2013, we decided to suspend treatment with baclofen (Lioresal®), replacing it with tizanidine and diazepam. After two weeks of tizanidine treatment, the patient stopped the drug because of drowsiness and spasticity was controlled only with diazepam.
10 months after the drug’s discontinuation, the patient had not re-experienced neurological symptoms.
DISCUSSION
Spasticity is a classic symptom in spinal injury patients. Baclofen is widely used in these patients, despite their high risk of neurotoxicity, as a result of having reduced renal function due to neurogenic bladder. We also have to bear in mind that, on assessing serum creatinine levels, we overestimated the renal function due to a decrease in muscular mass10.
Psychomotor agitation is a rare symptom of baclofen-induced encephalopathy. This encephalopathy usually manifests itself as a reduced level of consciousness. Our patient initially presented this symptom, since the same baclofen dose was used as in a patient with normal renal function. Following deterioration in renal function and the start of haemodialysis, the patient experienced the atypical symptom of psychomotor agitation.
In reviewing the literature, we observe that the pharmaco-dynamics of baclofen in dialysis patients is expressed as C = C0 + eKet, where Ke is dependent on the drug’s renal (Kr) and non-renal (Knr) metabolism. In dialysis patients, renal clearance is restricted to clearance during dialysis; thus Kr = Kd, where Kd = 0.291/h and Knr 0.045/h, therefore Ke = Kd + Knr = 0.336/h. Given the drug’s excretion, baclofen’s half life went from 15.5h in patients with stage 5 chronic renal failure not on dialysis to 2.06h in dialysis patients11-13.
We suspect that this patient’s clinical symptoms can be attributed to a sudden suppression of baclofen levels in blood. It is worth noting that similar cases have been described in sudden withdrawals of this drug in patients with intrathecal perfusions.14,15
Despite no clear indications about baclofen in pharmacological guides, we do not recommend the use of this drug in dialysis patients.
Conflicts of interest
The authors declare that they have no conflicts of interest related to the contents of this article.
