JH is a 66-year-old female who was recently discharged after receiving a few days of treatment for hospital-acquired pneumonia caused by MRSA. While working in your local community pharmacy, you receive a prescription written for Zyvox 600 mg PO BID for JH. 

PMH: 

Epilepsy

Dyslipidemia

Hypertension

Heart Failure with Preserved Ejection Fraction

Type 2 Diabetes Mellitus

Major Depressive Disorder

Allergy: Bactrim (rash)

Current Medication List:

Keppra 750 mg PO BID

Crestor 40 mg PO QD

Farxiga 10 mg PO QD

Prinivil 40 mg PO QD

Microzide 25 mg PO QD

Emsam 6 mg/24 hr transdermal patch QD

Vitals and labs from hospital upon discharge:

Wt: 88 kg

Ht: 5’6”

HR: 76 BPM

RR: 18 BPM

Temp: 99.2 F

Na: 141 mEq/L

K: 3.7 mEq/L

SCr: 0.7 mg/dL

BG: 126 mg/dL

WBC: 9.2 K

Platelets 200 K

Which of the following is true about Zyvox? Select all that apply.

A. Zyvox is inactivated by lung surfactant and is not recommended for the treatment of pneumonia.

B. Concomitant use of Zyvox and Emsam may increase the risk of serotonin syndrome.

C. Zyvox may cause peripheral and optic neuropathy with extended durations of therapy.

D. Zyvox may cause myelosupression in extended durations of therapy.

E. Zyvox’s mechanism of action involves binding to D-alanyl-D-alanine and inhibiting bacterial cell wall synthesis.

Staphylococcus aureus is a Gram-positive cocci that grows in clusters and can cause a variety of infections including pneumonia, endocarditis, and skin and soft tissue infections. Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of S. aureus that is resistant to penicillins and most cephalosporins, but some examples of antibiotics with activity against MRSA are vancomycin, ceftaroline, daptomycin, and linezolid. Quite simply- S. aureus is a pathogen that causes significant morbidity and mortality. Source control with invasive infections is critical to enhance critical cure along with antimicrobial therapy. 

Zyvox (linezolid) is an oxazolidinone that inhibits bacterial protein synthesis by binding to the 23S ribosomal RNA of the 50S ribosomal subunit. It’s available as an injection, tablet, and oral suspension and can be used to treat a variety of Gram-positive organisms including streptococcus, MSSA, MRSA, and VRE. As a pharmacist, it’s important to understand the benefits and risks of this agent compared to other available anti-MRSA antibiotics.

Answer choice A is incorrect. Zyvox is not inactivated by lung surfactant and can be used to treat pneumonia caused by susceptible Gram-positive bacteria. However, this statement does apply to the cyclic lipopeptide antibiotic daptomycin which is rendered ineffective for the treatment of pneumonia due to its interaction with pulmonary surfactant.

Answer choice B is correct. Zyvox acts as a weak nonselective MAOI and its use with MAOIs such as Emsam (selegiline) is contraindicated. Concomitant use with MAOIs, TCAs, SSRIs, or SNRIs increases the patient’s risk of serotonin syndrome. Although this adverse reaction is rare, it can be life-threatening, so patients should be monitored for symptoms such as palpitations, hyperreflexia, and altered mental status.

Answer choice C is correct. Peripheral and optic neuropathy most commonly occur after greater than 4 weeks of therapy. If signs of optic neuropathy such as sensitivity to bright lights or diminished vision clarity occur, the patient should receive a visual examination as soon as possible. Linezolid discontinuation usually reverses optic neuropathy but patients may not completely recover from peripheral neuropathy.

Answer choice D is correct. Myelosuppression may occur after greater than 2 weeks of therapy and is reversible after discontinuation. Weekly CBC monitoring is recommended with Zyvox use, especially after 2 weeks of continued treatment.

Answer choice E is incorrect. Zyvox's mechanism of action involves binding to the 50S ribosomal subunit to inhibit protein synthesis. However, this statement would apply to vancomycin which binds to D-alanyl-D-alanine to block glycopeptide polymerization and inhibit cell wall synthesis. Linezolid may be used in place of vancomycin in the hospital when treating pneumonia in patients with acute kidney injury as linezolid is not nephrotoxic unlike vancomycin. 

Medications: Zyvox (linezolid), Keppra (levetiracetam), Crestor (rosuvastatin), Farxiga (dapagliflozin), Prinivil (lisinopril), Microzide (HCTZ), Emsam (selegiline)

NAPLEX® Competencies:

Area 2 - Identify Drug Characteristics

2.1 - Pharmacology, mechanism of action, or therapeutic class

2.2 - Commercial availability; prescription or non-prescription status; brand, generic, or biosimilar names; physical descriptions; or how supplied

Area 3- Develop or Manage Treatment Plans

3.6 - Drug contraindications, allergies, or precautions

3.7 - Adverse drug effects, toxicology, or overdose

3.8 - Drug interactions

Area 5 - Compound dispense, or administer drugs, or manage delivery systems

5.1 - Physicochemical properties of drug products affecting compatibility, stability, delivery, absorption, onset, duration, distribution, metabolism, or elimination