Assalaamu alaykum. My friend wants to quit smoking, so he started taking nicotine gum and nicotine pills to lower the needs of smoking. Is that allowed as he is trying to quit?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

If this person cannot quit smoking through sound means and these gums and pills ultimately lead to quitting smoking, then there is nothing wrong with it.

Shaykh Ibn ‘Uthaymeen was asked, "In some pharmacies, they sell a patch that is placed on the body, giving the body its need of nicotine for 24 hours, as a step to quit smoking. The question is: if it is placed at night for twenty-four hours and then another one is put again, does this invalidate the fasting of the person using it in Ramadhaan?"

He replied:

"It does not break his fast in Ramadhaan, and it is permissible for him to use it; rather, it may be an obligation to use it if it is a means to quit smoking. It is acceptable for a person to gradually abandon what is forbidden, step by step, because when Allah wanted to forbid wine (alcohol), He did not forbid it at once, rather, He forbade it in steps: at first, He permitted it, then He clarified that its harm is greater, then He forbade it at some given times [times of the prayer], and finally, He totally forbade it. So there are four steps:

1 - Allah permitted it in the verse (which means): {And from the fruits of the palm trees and grapevines you take intoxicant and good provision. Indeed in that is a sign for a people who reason.} [Quran 16:67] This is in the context of conferring favor, so it is lawful.

2 - Allah hinted at its prohibition in His saying (which means): {They ask you about wine and gambling. Say, "In them is great sin and [yet, some] benefit for people. But their sin is greater than their benefit."} [Quran 2:219]

3 - He forbade it at some given times; Allah says (what means): {O you who have believed, do not approach prayer while you are intoxicated.} [Quran 4:43] This requires that we leave it when praying.

4 - Then Allah completely forbade it, as Allah says (what means): {O you who have believed, indeed, intoxicants, gambling, [sacrificing on] stone altars [to other than Allah], and divining arrows are but defilement from the work of Satan, so avoid it.} [Quran 5:90]

The verse prohibiting alcohol was revealed while the vessels of the companions were full of wine, so they took them (the vessels) out to the markets and poured out their contents. Praise be to Allah. What is the difference between us and them? The difference between us and them in complying (with the commandment) is like the difference between their time and our time. They did not falter. They did not say, we will drink whatever is left in the vessels; no, never. They had glasses in their hands, and they went out and poured them on the ground in the markets. They totally refrained from drinking alcohol. They did not say: We have become accustomed to it and so on. No, they totally abandoned it, because they had the will to overcome any adversity.” 

Allah knows best.