From the Research
For an 80-year-old male with impaired renal function (serum creatinine 1.2), the recommended initial IV dose of Robaxin (methocarbamol) should be reduced to 1 gram administered slowly over at least 1 minute, with careful monitoring. This dose adjustment is necessary due to the patient's age and mild renal impairment, as evidenced by the serum creatinine level of 1.2 1. The total daily dose should not exceed 3 grams for this patient, compared to the usual maximum of 3-6 grams daily. After initial treatment, reassess the patient's response and renal function before administering additional doses. Elderly patients and those with kidney impairment have reduced drug clearance, increasing the risk of adverse effects like dizziness, drowsiness, and hypotension 2. The medication should be discontinued if the patient experiences significant side effects. Methocarbamol works as a central muscle relaxant by depressing the central nervous system, and its metabolism and elimination are partially dependent on renal function, necessitating this dose adjustment. It is also important to consider the potential risks associated with the excipient polyethylene glycol (PEG) in IV methocarbamol, particularly in patients with renal impairment 3. However, the most recent and highest quality study on this topic is from 2024, which suggests that the risks associated with PEG may be debated 3. Regardless, careful monitoring and dose adjustment are crucial to minimize the risk of adverse effects in this patient population. Age-related changes in urinary creatinine excretion should also be considered when assessing renal function in elderly patients 4. In this case, the patient's serum creatinine level of 1.2 indicates mild renal impairment, which warrants a reduced dose of methocarbamol to minimize the risk of adverse effects. Overall, the recommended dose of 1 gram IV, administered slowly and with careful monitoring, is the most appropriate course of treatment for this patient.