Miss Weston had taken a concoction of Zyban, Chloroquine and sleeping pills containing Diphenhydramine, triggering a deadly reaction.
The Committee on Safety of Medicines (CSM) hopes to cut down the number of instances where patients suffer adverse reactions to the drug.
A coroner last month called for the manufacturers GlaxoSmithKline to improve warnings about mixing the drug with other medication.
Hertford coroner Alan Lawson recorded a verdict of death by natural causes on airline flight attendant Kerry Weston, 21, of Broxbourne, Herts who was found dead in her hotel room in Nairobi a fortnight after she was prescribed Zyban.
Miss Weston had taken a concoction of Zyban, Chloroquine and sleeping pills containing Diphenhydramine, triggering a deadly
reaction.
Since it was licensed in the UK in June 2000, Zyban has been prescribed to more than 419,000 people.
However, 37 people have died after taking the drug, and 5,352 adverse reactions have been logged under the government's "yellow card" scheme.
Prescribing rules
The CSM has decided that rules on prescribing the drug should be altered to stop the dosage being increased after three days.
Currently patients would take one tablet per day for three days and then two tablets per day from day four onwards.
In future the dosage will not be upped until day seven of the treatment regime.
The Committee also recommended that warnings relating to risk factors for seizures to doctors should be strengthened to "emphasise" that Zyban should only be used in patients with these factors if there are "compelling" clinical reasons.
The CSM, an independent expert advisory committee, said about 2% of adverse reports for all medicines are associated with a fatal outcome, but with Zyban the proportion of reports that are fatal is less than 1%.
Professor Alasdair Breckenridge, chair of the CSM, said: "As with all newly licensed medicines, Zyban has been carefully monitored under an intensive monitoring scheme.
"The changes to the prescribing regime and the strengthened warnings will help to further reduce the number of people who experienced adverse reactions whilst taking Zyban.
"The Committee on Safety of Medicines and the Medicines Control Agency, in conjunction with other European Regulatory Authorities, are taking this action today and will be keeping the safety of Zyban under close, constant scrutiny."
A letter has been sent to all GPs, pharmacists and smoking cessation clinics to advise them of the changes.
Wonder drug
Zyban is the first non-nicotine anti-smoking treatment to receive a licence in the UK.
It works by altering the chemical balance in smokers' brains.
Clinical trials had shown that a third of people taking the prescription pills had managed to kick the habit for more than a year, making it twice as effective as nicotine patches.
GlaxoSmithKline issued a statement which said the company was committed to ensuring prescribers and patients receive clear information about Zyban.
The statement said: "Smoking is the single greatest cause of premature death in the UK, and is responsible for 120,000 deaths per year.
"GlaxoSmithKline believes Zyban has a major role to play in reducing the considerable disease burden and mortality associated with smoking."