C3.2 R4(c): Clarify a medication order with a prescriber #3

Discussed and clarified order with prescriber.

Pharmacy Clarification Order:

  1. Discontinue magnesium hydroxide

Clinical Pharmacy Note RE: Medication adjustment for low renal function

ID: 79 yo female with a long-standing history of bipolar depression
and MCI along with multiple medical comorbidities, including chronic renal
failure and hypothyroidism


  1. Chronic renal failure (eGFR = 16mL/min on Sept 19/16)
  2. Recurrent bipolar depression and history of depression
    – on venlafaxine long acting 150mg PO daily
  3. On bowel protocol, includes magnesium hydroxide PO PRN

v/s (Sept 20/16): Temp 36.6, BP 171/91, HR 62, RR 16, O2 sats 99%RA
Has not required any use of PRN laxatives during her stay


  1. Magnesium: Lexicomp and CPhA monograph: patients with severe renal impariemnt should avoid magnesium due to toxicity from accumulation (e.g. N/V/D, cardiac arrhythmias)
  2. Other laxatives PRN (e.g. lactulose, PEG) do not require renal impairment adjustment
  3. Venlafaxine: Lexicomp states to decrease dose by 50% or more if CrCl < 30mL/min, and CPhA monograph states to decrease dose by 25-50% if eGFR = 10-70mL/min
  4. Max daily dose of venlafaxine XR = 225mg
    Therefore, max daily dose for her renal function: 112.5-168.75mg


  1. Discontinue Mg Hydroxide PRN (DONE)
  2. Continue venlafaxine long acting 150mg PO daily
  3. Monitor for SEs of venlafaxine: headache, insomnia, dizziness, nausea, anorexia, and consider dose decrease if appropriate.

Thank you!
Shermaine Ngo, BSc. Pharm

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