Combination leads to higher smoking cessation compared with single‐form nicotine replacement therapy (high certainty).
Combination showed no clear difference in overall serious adverse events compared with single‐form nicotine replacement therapy (low certainty).
It is very uncertain whether combination changes treatment withdrawals compared with single‐form nicotine replacement therapy (very low certainty).
The intervention showed no clear difference in combination NRT & bupropion versus placebo Smoking cessation (low certainty).
Reduction and pharmacotherapy showed no clear difference in subgroup: combination NRT; smoking cessation (≥ 6 month compared with reduction alone (low certainty).
Varenicline showed no clear difference in smoking abstinence at longest compared with combination nicotine replacement therapy (low certainty).
Varenicline showed no clear difference in SAEs compared with combination nicotine replacement therapy (low certainty).
Varenicline showed no clear difference in neuropsychiatric SAEs compared with combination nicotine replacement therapy (low certainty).
Varenicline showed no clear difference in cardiac SAEs compared with combination nicotine replacement therapy (low certainty).
It is very uncertain whether longer changes smoking cessation ‐ 16 weeks versus 8 weeks compared with shorter duration of combination nicotine replacement therapy (very low certainty).
Longer showed no clear difference in smoking cessation ‐ 6 weeks versus 2 weeks compared with shorter duration of combination nicotine replacement therapy (low certainty).
It is very uncertain whether longer changes overall SAEs ‐ 26 weeks versus 8 weeks compared with shorter duration of combination nicotine replacement therapy (very low certainty).