C3.1 R4(e): Perform & document a vancomycin or aminoglycoside pharmacokinetic interpretation

Nov 2/2015 (1230hr) Clinical Pharmacy Note

ID: 54 yo male with Fournier Gangrene admitted on Oct 29/16

s/o: Abx:

  1. Pip/Taz 3.375mg IV Q6H
  2. Vancomycin 1g IV Q12H
    Both started since Oct 29/16

Micro: BCx (Oct 29): -, MRSA swabs (Oct 31): -, Urine Cx (Oct 29): -, Ascitic Fluid (Oct 29): –
No cultures done for debridgement of penis scrotum and perineum

Labs:                     Oct 31                Nov 1                 Nov 2
sCr                          96                       143                     114
eGFR                      77                       48                       63
WBC                       16.9                    19.2                    15.4
Neuts                     12.8                    13.2                    11.8

Vanco trough level: 23.2 mg/L (pre 6th dose at 3S)

A:

  1. No cultures to guide need for vancomycin but low risk for MRSA as swabs are negative on Oct 31/16
  2. Level is supratherapeutic and at steady state (target: 15-20mg/L). Level drawn and doses given appropriately. Level likely increased due to accumulation caused by AKI
  3. Renal fx improved with NS bolus, albumin and holding off diuretics yesterday. Starting midodrine and octreotide today. Renal function will likely be unstable over next few days

P:

  1. Decrease vancomycin dose to 750mg IV Q12H (at 100hr and 2300hr)
  2. Monitor renal function, CBCs + diffs daily and assess pre-4th 750mg IV dose trough level
  3. Suggest: R/A vancomycin as MRSA swabs (-)

Nov 7/2016 (1550hr) Clinical Pharmacy Note

ID: 54 yo male admitted on Oct 29/16 for Fournier Gangrene

s/o: Currently on vancomycin 750mg IV Q12H + Pip/Taz 3.375mg IV Q6H
Vital signs (Nov 7):

Labs:                     Nov 5                Nov 6                 Nov 7
sCr                          97                       98                       64
eGFR                      79                       76                       112
WBC                       8.3                     9.0                      15.0
Neuts                     5.3                      5.6                      10.6

Vancomycin trough level (Nov 7/16): 14.8mg/L (was 17.0mg/L on Nov 4/16)
No new cultures since last level

A:

  1. Vancomycin for empiric coverage of Fournier Gangrene until Nov 15/16
  2. All doses are given and levels drawn appropriately. Level is at steady state
  3. As per nurse, patient is very edematous and urine output is very low. This is reflected by his recent increase in serum creatinine. If patient is volume overloaded, this may also explain his increase in WBC and CBCs.
  4. Vancomycin level is slightly subtherapeutic (target: 15-20mg/L). However, there is a risk of accumulation with AKI

P:

  1. Continue current dose of vancomycin 750mg IV Q12H
  2. Monitor renal function, CBCs and diffs daily
  3. Order vancomycin trough level pre-6AM dose on Nov 9

Order:

  • Change vancomycin dose to 750mg IV Q12H. Start dose at 1300hr
    • Pharmacy: please schedule on MAR at 1AM, 1PM
  • Vancomycin trough level prior to 1AM dose on Nov 4 (i.e. Pre 4th dose of 750mg IV dose)
  • Pharmacy will continue to follow.

For DR___ (ID, per Rx to dose). Pharmacist

Notes:

  • If discontinue vancomycin and start new vancomycin order, will be changing stop dates

C3.1 R4(e): Perform & document a vancomycin or aminoglycoside pharmacokinetic interpretation

ID: 42 yo female admitted for query septic arthritis/deep tissue infection/myositis

s/o:
Current Abx Therapy:

  1. Pip/Taz 3.375mg IV Q6H
  2. Vancomycin 2g IV Loading Dose x 1 dose on August 31 1530
    Currently on 1g IV Q12H (at 330, 1530)

Vital Signs (Sept 2/16): Temp 37.4, BP 119/79, HR 99, RR 18, O2 sats 95% RA
(receives APAP PRN for pain)

Labs:
↓ WBC (Aug 31: 22.2 –> Sept 2: 10.5)
↓ sCr (Aug 31: 98 –> Sept 2: 45)
↑ eGFR (Aug 31: 62 –> Sept 2: 118)

Micro: MRSA screen pending. Blood Cxs on Aug 31/16 are negative.
Urine Cxs + For E. Coli 90 mega CFU/L

Vanco trough level: 6.2 mg/L (target 15-20mg/L)
– drawn 30 mins prior to Sept 2 330 dose (4th dose, including LD)

A/Checklist:

  1. Is the drug indicated?: Although patient is improving (decreased WBC, afebrile, improving overall) and is tolerating vancomycin (urinating well, no compliants, sCr stable), cultures are still pending.
  2. Were all the doses given on time?: All doses were given on time
  3. Was the level drawn at steady state?: Trough level was at steady state (pre-4th dose)
  4. Was the level drawn appropriately?: Level was drawn appropriately 30 mins prior to the 4th dose
  5. Assess the level: Vanco trough level = 6.2, which is below target

P: As discussed with MD:

  1. Discontinue previous vancomycin IV orders.
  2. Increase vancomycin to 1.25g IV Q8H – next dose due at 1530 today
  3. Vancomycin level on Sept 3 at 1500 (30 mins prior to 1530 dose)
  4. Will continue to monitor: renal function, temperature, pain/swelling, WBC, CRP
  5. Pharmacy will continue to follow and adjust dose accordingly. MD to reassess need for vancomycin.

Rationale for vancomycin 1.25g IV Q8H:

  • Improving renal function requires increased frequency (Q8H) to ensure concentrations stay above vancomycin’s MIC
  • Following linear pharmacokinetics:
    • Would expect that we would need to target a daily dose of ~5500mg
      (~1800g IV Q8H)
  • Although we want to ideally target 15-20mg/L, the benefits of ~doubling the dose to target 15-20mg/L likely won’t outweigh the risks (e.g. risk of accumulation
    → increased risk of nephrotoxicity and ototoxicity) when the patient is already improving at a significantly sub-therapeutic level.
  • Therefore: ↑ dosing frequency and ↑ the dose by 250mg (minimum dosing increment)
  • Keeping in mind: patient improving at sub-therapeutic level may indicate that patient is improving on other antibiotic therapy and that coverage against MRSA may not be warranted. Pharmacy should follow up with MRSA screen.