0 sources cited

Bupropion Mechanism Of Action: How Does Wellbutrin Work?

Last Updated: February 22, 2024

Authored by Nena Messina, Ph.D.

Reviewed by David Levin

Bupropion(Wellbutrin) is a well-known aminoketone antidepressant. Wellbutrin is used for treating symptoms of moderate to severe depressive disorders and as a supporting medicine in smoking cessation. How long does it take for Wellbutrin to work? Find out what the bupropion mechanism of action is and how it can be used safely for improving one’s mental health conditions.

Bupropion Mechanism Of Action

Bupropion class is a norepinephrine-dopamine reuptake inhibitor (NDRI). According to a study about the pharmacology and therapeutic applications of bupropion, its mechanism of action is known for inhibiting the reuptake of the neurotransmitters dopamine and norepinephrine. It works by binding with the norepinephrine transporter (NET) and dopamine transporter (DAT).
These neurotransmitters help in regulating sleep, mood, pleasure, memory retrieval, arousal, and restlessness. When these neurotransmitters are decreased, this results in depression, seasonal affective disorder (SAD), and other depressive disorders.

doctor explaining bupropion moa to a male patient
Wellbutrin works by inhibiting dopamine and norepinephrine reuptake resulting in a longer duration for them to act in the brain. This helps in reversing the effects of depression.
Unlike Selective Serotonin Reuptake Inhibitors mechanism of action, when using Wellbutrin, serotonin reuptake is not inhibited. This results in much lesser Wellbutrin sexual side effects, which are typical when a patient is taking SSRIs, but problems with weight gain, are still present.

How Fast Does Bupropion Work?

Wellbutrin is a type of medicine which does not start working immediately as well as the majority of other antidepressants. The time Wellbutrin takes to start working depends on its dosage and frequency for which it is being taken.

How Fast Does Wellbutrin Work For Depression?

After patients start taking Wellbutrin for Major depression disorder, they can notice an improvement in their appetite and sleep-related issues after 1-2 weeks of use. The feeling of general well-being and a positive attitude towards everything may be experienced after regular use of the medication for at least 4-6 weeks.

How Fast Does It Work For Smoking Cessation?

For use in quitting smoking, Wellbutrin mechanism of action decreases the craving for nicotine. According to the study about the clinical profile of bupropion, it inhibits DAT and NET and acts as the nAChR antagonist, which contributes towards it being a tobacco use cessation agent. A patient should also start taking the medication daily for one-two weeks before they quit smoking. In another way, there is a high risk that the drug won’t work for decreasing the cravings.

Except it is a slow-acting drug, it’s exertion is not instant as well. Bupropion half-life is approximately 12-30 hours. This period also depends on the dosage taken and the overall duration of the treatment course.

woman breaking cigarette in hands

What Are Wellbutrin Ingredients?

The active ingredient in Wellbutrin is bupropion Hydrochloride in the labeled amount in addition to other inactive ingredients. Wellbutrin is available in three different formulations: Immediate-Release (IR), Sustained-Release (SR), and Extended-Release (XL). The details of primary ingredients in these formulations and differences in their mechanism of action are listed below. Some ingredients in bupropion releases may differ between manufacturers, and a physician should always be asked before taking any of them.

What Is In Wellbutrin IR?

Immediate Release contains the following ingredients:

  • Bupropion Hydrochloride
  • D&C Yellow No. 10 Lake for the 75 mg tablet whereas FD&C Red No. 40 Lake for the 100 mg tablet
  • FD&C Yellow No. 6 Lake
  • Hydroxypropyl cellulose
  • Hypromellose
  • Microcrystalline cellulose
  • Polyethylene glycol
  • Talc
  • Titanium dioxide

Wellbutrin IR mechanism of action is known for acting faster than the other formulations. Based on the pharmacokinetics of bupropion in three different formulations, IR is absorbed more rapidly. The Tmax for IR is 1 hour, whereas that of SR and XL are 3 and 5 hours respectively. However, its effects also start to wear off relatively faster, which means it has to be taken at least thrice a day for it to be effective.

What Is In Wellbutrin SR?

SR contains the following ingredients:

  • Bupropion Hydrochloride
  • Carnauba wax
  • Cysteine hydrochloride
  • Hypromellose
  • Magnesium stearate
  • Microcrystalline cellulose
  • Polyethylene glycol
  • Polysorbate 80
  • Titanium dioxide

Bupropion SR is a controlled-release formulation whose effects last for 12 hours. Wellbutrin is to be taken twice a day when it is used in the sustained-release formulation. Bupropion SR dissolves relatively slower than the IR version.

What Is In Wellbutrin XL?

XL formulation contains the following ingredients:

  • Bupropion hydrochloride
  • Ethylcellulose
  • Glyceryl behenate
  • Methacrylic acid copolymer dispersion
  • Polyvinyl alcohol
  • Polyethylene glycol
  • Povidone
  • Silicone dioxide
  • Triethyl citrate

The extended-release of bupropion mechanism of action enables the drug effects to last for 24 hours. Wellbutrin XL 150 mg or Wellbutrin XL 300 mg has to be taken once a day upon prescription. The extended release version is different from the sustained release version in that it dissolves even slower than SR. This results in relatively lesser side effects of bupropion and is easily tolerated. Wellbutrin SR and XL formulations are released slowly and have a lower absorption rate in the GI tract as compared to the IR formulation. This makes them last longer than Wellbutrin IR.

three brown medicine bottles filled with different bupropion pills

Taking Bupropion Safely

When used according to the prescription of a doctor, this medicine is proven to be an effective medication for MDD treatment, with quite easily manageable side-effects. But without medical guidance, Wellbutrin intake can lead to several health risks.

As bupropion mechanism of action makes changes in the level of dopamine in the brain and causes stimulant-like effects. Because of these effects, it can be used to get bupropion HCL high by some individuals, and it has the potential of being abused. Wellbutrin is usually taken for an extended period, and during this period, psychological dependency on bupropion may also develop.

Withdrawal from Wellbutrin is usually started with a tapering schedule developed by addiction treatment professionals. Detoxification procedures will also help a patient to avoid severe withdrawal symptoms.

Page Sources

  1. Foley KF, DeSanty KP, Kast RE., Bupropion: pharmacology and therapeutic applications, https://www.ncbi.nlm.nih.gov/pubmed/17009913
  2. Linda P. Dwoskin, Anthony S. Rauhut, Kelley A. King-Pospisil, Michael T. Bardo, Review of the Pharmacology and Clinical Profile of Bupropion, an Antidepressant and Tobacco Use Cessation Agent, https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1527-3458.2006.00178.x

Published on: February 22nd, 2024

Updated on: February 22nd, 2024

About Author

Nena Messina, Ph.D.

Nena Messina is a specialist in drug-related domestic violence. She devoted her life to the study of the connection between crime, mental health, and substance abuse. Apart from her work as management at addiction center, Nena regularly takes part in the educational program as a lecturer.

Medically Reviewed by

David Levin


Leave a comment

Free Insurance Verification

Our team is available to guide you through the steps of assessing your insurance coverage for addiction treatment.