Accessing NPM module from Node using admin privileges (sudo)

I'm trying to write a Node script that makes use of the NPM API. The script works, but requires admin access for certain modules to be installed. I tried running the script with sudo, but it fails on the line requiring NPM.

I distilled it to the following simple script:

var npm = require('npm'),
    assert = require('assert');

assert.notEqual(npm, null, 'NPM is null');

Running this script regularly with node npm.js works, running it with sudo node npm.js throws the following:

Error: Cannot find module 'npm'
    at Function.Module._resolveFilename (module.js:338:15)
    at Function.Module._load (module.js:280:25)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (/Projects/MyNPM/npm.js:1:73)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10) 

What am I missing, and what happens to the path structure when I use sudo?