Why The Boom prescribes Mounjaro, not Wegovy, in Busan.

Patients arrive at our Busan skin clinic asking for one by name and leave understanding why we prescribe the other, or occasionally why neither. Mounjaro and Wegovy are the two weekly injections that changed weight management, and the marketing has blurred a real pharmacological difference into a brand preference. This guide sets the two beside each other, with the evidence, the Korean rules that apply to both, and the honest reason an internal medicine specialist in Seomyeon chose to prescribe one.

All five come up every week. This page answers them in order.

What are Mounjaro and Wegovy, and how do they differ?

Wegovy is semaglutide, a GLP-1 receptor agonist: it mimics one gut hormone that slows stomach emptying, reduces appetite and improves the body's handling of sugar. Mounjaro is tirzepatide, a dual GLP-1 and GIP receptor agonist: it mimics two gut hormones, adding GIP, which acts on fat tissue and on insulin signalling in ways still being worked out, and which in practice adds to the appetite effect. Both are once-weekly pens, both are started low and stepped up every four weeks, and both are licensed in Korea for weight management under the same BMI criteria. The difference is one hormone, and it is not a marketing difference.

What does the evidence say about Mounjaro vs Wegovy, honestly?

The two were compared directly in a randomised trial in adults with obesity and without diabetes, and tirzepatide produced a larger average weight loss than semaglutide over the same period, by a margin large enough to matter clinically rather than statistically. Earlier single-drug trials pointed the same way: the tirzepatide programme reported larger average losses at its top dose than the semaglutide programme at its. Averages hide individuals, and some patients do as well on semaglutide as others do on tirzepatide, but a doctor choosing one drug to prescribe for most patients is choosing by the average, and the average favours Mounjaro.

What the evidence does not say: that one is safer. The side-effect profiles are the same family, gastrointestinal, worst at step-up, settling for most; the contraindications are the same list; the long-term questions, what happens after stopping, who regains and how fast, are open for both. Semaglutide has the longer record and a cardiovascular outcome trial behind it; tirzepatide's outcome data are newer. Our Seomyeon skin clinic says all of that before the first pen.

Why does The Boom in Seomyeon, Busan prescribe Mounjaro?

Three reasons, in order. The average result , as above: for a clinic that assesses and follows patients one month at a time, the drug with the larger expected loss per month of side effects is the better default. One drug, well : an internal medicine specialist prescribing one medicine to every weight patient knows its step-up, its nausea curve and its plateau in detail, and a patient in Busan gets that depth rather than a menu. Supply and continuity : the pharmacy next door stocks Mounjaro at every strength, so a visitor continuing a dose from home and a resident on month six are served from the same shelf; a clinic offering both drugs splits that.

What the reason is not: price, which is the pharmacy's and not ours, or a commercial arrangement, of which there is none. The cost guide sets out who charges what.

When is Wegovy the better answer, and what do we do then?

Three cases. A patient who has tolerated semaglutide well for a year and has no reason to change: switching them for the sake of our default would be bad medicine, and we say so and refer them to a prescriber who continues it. A patient with a specific reason tirzepatide is unsuitable, which the assessment finds. And a patient whose prescriber at home has chosen semaglutide for a cardiovascular reason the outcome trial supports. In each case our Busan skin clinic says plainly that Wegovy is the right drug and that we do not prescribe it, and points to where it is prescribed; a clinic that switches every patient to its own default is not reading the patient.

Can you switch from Wegovy to Mounjaro in Busan?

Common, and done carefully. There is no direct dose conversion between the two; a patient on 2.4 mg of semaglutide is not started on 15 mg of tirzepatide. The doctor takes the history, confirms the criteria as for any patient, and starts Mounjaro at a low dose, usually 2.5 or 5 mg, the week after the last semaglutide dose, stepping up by tolerance. Nausea at the switch is common for a fortnight and settles. Bring evidence of your Wegovy dose and how long you have been on it; it changes the starting point.

What is the same for both in Korea: rules, criteria, side effects?

Everything that matters legally. Both are prescription-only, assessed in person, prescribed for a month at a time and dispensed by a pharmacy, under the same BMI criteria, with the same contraindications: pregnancy, medullary thyroid cancer or MEN2 in the history, pancreatitis, type 1 diabetes without a prescriber. Both cause nausea, reduced appetite and bowel changes in the first weeks and after step-ups, and both carry the rare serious risks of pancreatitis and gallbladder disease. The international patients guide covers the process, and it is the same process whichever pen you would have preferred.

What does neither drug do: the face and the pockets?

Neither chooses where the fat comes off, and both empty the face before the body: hollow temples, deeper folds, a looser jawline at a weight the scale is happy with. Neither reaches the structural pockets, the submental fat under the chin, the bra line, the inner knee, that genetics keeps. Those are skin-clinic problems and the reason a skin clinic in Busan prescribes the medicine at all: the doctor who writes the prescription also plans the face once the weight settles, with Sculptra, filler and lifting devices, and the pockets with fat-dissolving injections timed to the dose. Whichever drug, that part is the same, and it is the part no pharmacy sells.