It is essential that a patient's renal function is taken into account when prescribing and reviewing medication. Doses often need to be reduced in renal impairment to prevent accumulation and toxicity. Examples of drugs that should be reduced in renal impairment are the gabapentinoids: gabapentin and pregabalin.
Table 1 shows maximum recommended dose of gabapentin in renal impairment:
Table 1. Maximum gabapentin in renal impairment
| Renal function eGFR/mL per minute per 1.73 m2 | Maximum daily dose (to be administered as three divided doses) |
|---|---|
| 50-79 mL per minute per 1.73 m2 | 1800 mg |
| 30-49 mL per minute per 1.73 m2 | 900 mg |
| 15-29 mL per minute per 1.73 m2 | 600 mg |
| <15 mL per minute per 1.73 m2 | 300 mg |
Table 2 shows the maximum recommended dose of pregabalin in renal impairment:
Table 2. Maximum recommended dose of pregabalin in renal impairment
| 30-60 mL per minute per 1.73 m2 | 300 mg (in two to three divided doses) |
| 30-60 mL per minute per 1.73 m2 | 150 mg (in one to two divided doses) |
| <15 mL per minute per 1.73 m2 | 75 mg once daily |
In this scenario you are carrying out an audit of gabapentinoid prescribing in your work area, to ensure that the doses prescribed in renal impairment are safe and appropriate.
Your audit of the prescription records of 26 patients revealed the following doses:
PREGABALIN WITH EGFR 30-60
- Pregabalin 25 mg capsules: One to be taken twice a day
- Pregabalin 25 mg capsul: Two to be taken in the morning and one to be taken at night
- Pregabalin 100 mg capsules: one to be taken twice a day
- Pregabalin 50 mg capsules: one to be taken twice a day
- Pregabalin 75 mg capsules: one to be taken twice a day
- Pregabalin 50 mg capsules: one to be taken three times a day
- Pregabalin 75 mg capsules: one to be taken twice a day
- Pregabalin 75 mg capsul: one to be taken twice a day
- Pregabalin 25 mg capsules: one to be taken twice a day
- Pregabalin 10 0mg capsules: one to be taken three times a day
- Pregabalin 200 mg capsules: one to be taken three times a day
PREGABALIN WITH EGFR <15
- Pregabalin 75 mg capsules: one to be taken three times a day
GABAPENTIN EGFR 50-79
- Gabapentin 100 mg capsules: one to be taken three times a day
- Gabapentin 300 mg capsules: two in the morning, one in the afternoon, one in the evening.
- Gabapentin 100 mg capsules: one to be taken three times a day
- Gabapentin 300 mg capsules: One to three to be taken three times a day
- Gabapentin 300 mg capsules: One to be taken twice daily
- Gabapentin 300 mg capsules: One each morning and one each night
- Gabapentin 100 mg capsules: two to be taken twice a day
GABAPENTIN EGFR 30-49
- Gabapentin 100 mg capsules: one to be taken each day
- Gabapentin 300 mg capsules: take 7 tablets daily as directed
- Gabapentin 100 mg capsules: two tablets to be taken three times a day
- Gabapentin 100 mg capsules: two to be taken three times a day
- Gabapentin 100 mg capsules: one to be taken morning and lunch time and two to be taken at teatime
- Gabapentin 300 mg capsules: one to be taken three times a day
- Gabapentin 100 mg capsules: one to be taken at morning and teatime and two at night.
Review the doses and identify patients that require a consultation to have their doses adjusted.
You may incidentally notice some doses that require clarification. Potentially, you may consider that the quality of ‘directions’ on prescriptions could be audited in future!