The reaction usually appears within 4 to 10 min after the commencement or soon after the completion of an infusion and is characterized by flushing and/or an erythematous rash that affects the face, neck, and upper torso, attributed due to release of histamine from the mast cells. These findings are due to interaction of vancomycin with MRGPRX2, a GPCR mediating IgE-independent mast cell degranulation. Less frequently, hypotension and angioedema may also occur. Symptoms may be treated or prevented with antihistamines, including diphenhydramine, and are less likely to occur with slow infusion. Therapeutic drug monitoring
Plasma level monitoring of vancomycin is necessary due to the drugs biexponential distribution, intermediate hydrophilicity, and potential for ototoxicity and nephrotoxicity, especially in populations with poor renal function and/or increased propensity to bacterial infection. Vancomycin activity is considered to be time-dependent; that is, antimicrobial activity depends on the duration that the serum drug concentration exceeds the minimum inhibitory concentration  of the target organism. Thus, peak serum levels have not been shown to correlate with efficacy or toxicity; indeed, concentration monitoring is unnecessary in most cases. Circumstances in which therapeutic drug monitoring  is warranted include: patients receiving concomitant aminoglycoside therapy, patients with (potentially) altered pharmacokinetic parameters, patients on haemodialysis, patients administered high-dose or prolonged treatment, and patients with impaired renal function. In such cases, trough concentrations are measured.Target ranges for serum vancomycin concentrations have changed over the years.
Such measurements can be useful to avoid central nervous system toxicity in any person receiving large doses of the drug on a chronic basis, but they are especially relevant to patients with kidney failure, who may accumulate the drug due to reduced urinary excretion rates. Manufacture
The production of benzylpenicillin involves fermentation, recovery and purification of the penicillin.The fermentation process of the production of benzylpenicillin creates the product. The presence of the product in solution inhibits the reaction and reduces the product rate and yield. Thus, in order to obtain the most product and increase the rate of reaction, it is continuously extracted. This is done by mixing the mold with either glucose, sucrose, lactose, starch, or dextrin, nitrate, ammonium salt, corn steep liquor, peptone, meat or yeast extract, and small amounts of inorganic salts.The recovery of the benzylpenicillin is the most important part of the production process because it affects the later purification steps if done incorrectly. There are several types of techniques used to recover benzyl penicillin: aqueous two-phase extraction, liquid membrane extraction, microfiltration, and solvent extraction. Extraction is more commonly used in the recovery process.In the purification step, the benzylpencillin is separated from the extraction solution. This is normally done by using a separation column. Synonyms
Penicillin II (old UK nomenclature for naming penicillins)

References
External links
"Benzylpenicillin". Drug Information Portal. U.S. National Library of Medicine.