Typically a linear relationship such as

  
    
      
        
          y
          
            i
          
        
        =
        
          a
          
            0
          
        
        +
        
          a
          
            1
          
        
        
          x
          
            1
            ,
            i
          
        
        +
        
          a
          
            2
          
        
        
          x
          
            2
            ,
            i
          
        
        +
        ⋯
        +
        
          a
          
            k
          
        
        
          x
          
            k
            ,
            i
          
        
        +
        
          e
          
            i
          
        
      
    
    {\displaystyle y_{i}=a_{0}+a_{1}x_{1,i}+a_{2}x_{2,i}+\dots +a_{k}x_{k,i}+e_{i}}
  is postulated, in which 
  
    
      
        
          y
          
            i
          
        
      
    
    {\displaystyle y_{i}}
   is the ith observation of the dependent variable (hypothesized to be the caused variable), 
  
    
      
        
          x
          
            j
            ,
            i
          
        
      
    
    {\displaystyle x_{j,i}}
   for j=1,...,k is the ith observation on the jth independent variable (hypothesized to be a causative variable), and 
  
    
      
        
          e
          
            i
          
        
      
    
    {\displaystyle e_{i}}
   is the error term for the ith observation (containing the combined effects of all other causative variables, which must be uncorrelated with the included independent variables).
MNP belongs to the nitrosamine class of compounds, some of which are classified as probable or possible human carcinogens (substances that could cause cancer), based on laboratory tests such as rodent carcinogenicity studies. Although there are no data available to directly evaluate the carcinogenic potential of MNP, information available on closely related nitrosamine compounds was used to calculate lifetime exposure limits for MNP.As of January 2021, the FDA continues to investigate the presence of 1-methyl-4-nitrosopiperazine (MNP) in rifampin or 1-cyclopentyl-4-nitrosopiperazine (CPNP) in rifapentine approved for sale in the US. Names
Rifampicin is the INN and BAN, while rifampin is the USAN. Rifampicin may be abbreviated R, RMP, RA, RF, or RIF (US). Rifampicin is also known as rifaldazine, rofact, and rifampin in the United States, also as rifamycin SV.Its chemical name is 5,6,9,17,19,21-hexahydroxy-23-methoxy-2,4,12,16,18,20,22-heptamethyl-8-[N-(4-methyl-1-piperazinyl)formimidoyl]-2,7-(epoxypentadeca[1,11,13]trienimino)-naphtho[2,1-b]furan-1,11(2H)-dione 21-acetate. Rifampicin is available under many brand names worldwide. References
External links
"Rifampicin". Drug Information Portal. U.S. National Library of Medicine.