Vancomycin Pharmacology Made Easy

Vancomycin (Vancocin; FIRST-Vancomycin) is a drug used in the treatment of bacterial infections, often severe. It belongs to the glycopeptide drug class and has proved to be one of the most effective drugs in the treatment of many different infections.

Vancomycin is used in the treatment of severe Gram-positive infections, including:

• Endocarditis
• Osteomyelitis
• Abdominal infections
• Skin and soft tissue infections
• MRSA
• Pseudomembranous colitis caused by C. difficile
• Treatment of Gram-positive infections in patients who are allergic to penicillins
• Surgical prophylaxis where there is a risk of MRSA or MRSE

Vancomycin may also be used for other clinical purposes not listed in this guide, as determined by the prescriber.

Mechanism of Action

In terms of vancomycin pharmacology, the drug works by inhibiting cell wall synthesis of Gram-positive bacteria.

It achieves this by inhibiting the growth and cross-linkage of peptidoglycan strands. Therefore, vancomycin specifically targets Gram-positive organisms and is inactive against most Gram-negative bacteria – whose cell wall structure contains lipopolysaccharides.

However, resistance is on the rise.

One of the most common resistance methods by bacteria is to modify the structure of the cell wall to prevent vancomycin binding.

Side Effects of Vancomycin

Vancomycin is associated with the following range of side effects:

• Thrombophlebitis – if administered by infusion. For this reason, vancomycin should not be administered too rapidly otherwise serious infusion reactions can take place.
• “Red man syndrome” – is the name given to one of these anaphylactoid reactions. As the name suggests, it causes upper body erythema – as well as pruritis. This reaction can, in some cases, descend to the lower extremities, too. Hypotension and bronchospasm may also present.
• Nephrotoxicity – particularly with IV use.
• Ototoxicity – again, with IV use. Hearing loss can, in some cases, be permanent.
• Bone marrow suppression – neutropenia, leucopenia.

Of course, the risk of nephrotoxicity and ototoxicity is low, though this risk increases if taken with other drugs – such as aminoglycosides – that also have the potential to cause these effects.

Clinical Factors

In terms of the clinical pharmacology of vancomycin, here are some important factors to consider:

• That, as we have learned above, the risk of ototoxicity and nephrotoxicity is enhanced if taken with other drugs – for either one of these side effects – that are also associated with hearing loss and kidney damage. Macrolides, at high doses, for example, can cause ototoxicity. Loop diuretics and platinum chemotherapy also increase the risk of hearing loss.
• As a large hydrophilic molecule, vancomycin is not absorbed by the gastrointestinal tract. It either works locally in the intestine – such as in pseudomembranous colitis – or it must be administered IV for systemic use.
• To reduce thrombophlebitis and injection pain, vancomycin should be administered in a dilute solution, slowly, over (at least) a 1-hour period. Infusing vancomycin over a long period also helps prevent red man syndrome.
• Vancomycin requires therapeutic drug monitoring (TDM) to avoid toxicity. Dose adjustments should be made accordingly. Patients with extant renal disease may warrant a dose reduction. Elderly patients are at an increased risk of hearing loss, too, and may require dose reduction. Plasma concentrations should ideally be above 10mg/L but below 15mg/L to avoid toxicity.

That completes our review of vancomycin pharmacology.

If you would like to test your knowledge of vancomycin and every other antibacterial drug, register to become a member of NAPLEX Study Guide today – your leading online platform that teaches you the clinical details about medicines you need to know.