Clinical trials are essential. They establish whether a medication works, how strongly, and at what cost in side effects. Without trials, no responsible regulator approves a medication and no responsible doctor prescribes one.
But trials are not the whole story. Trial populations are selected. Trial conditions are controlled. Adherence in trials is monitored more closely than in real practice. Side effects are catalogued more systematically. The picture trials produce is true but somewhat idealised.
Real world data is what accumulates after a medication enters routine use. Eighteen months into the SA tirzepatide story, real world experience has accumulated enough to be meaningful. This is a look at what the practical experience has shown alongside what the SURPASS and SURMOUNT programmes established.
Adherence Is Higher Than Expected
One concern with weekly injection medications is whether patients will continue using them long term. Self-injection medications have historically had moderate adherence rates. Daily injection medications often see significant drop off within months.
The real world experience with tirzepatide globally and in SA suggests adherence is higher than typical. Several factors plausibly contribute:
- Weekly rather than daily dosing reduces the practical burden
- The KwikPen is designed for easy self-injection
- The early appetite reduction effect is rewarding enough that many patients want to continue
- Weight reduction provides ongoing motivation that other medications often lack
- The cost commitment selects for patients who are motivated to continue
The real world dropout rate from tirzepatide treatment appears to be substantially lower than typical for chronic medications, although still meaningful.
Side Effects Are Largely As Predicted
The side effect profile in SA practice matches the trial reports closely. Nausea is universal in the first month for most patients. Most settles within weeks. The serious but rare side effects (pancreatitis, gallbladder issues, severe kidney injury) appear at roughly trial rates.
One area where real world experience has been somewhat reassuring is the mental health signal. Postmarketing reports of depression and suicidal ideation in patients on GLP-1 medications raised concerns globally. The SA experience so far has not shown a clear elevated signal, although the population using the medication is still relatively small and the medication has only been available for 18 months. This will become clearer with more time.
Weight Outcomes Track Trial Averages
SURMOUNT-1 produced 20 percent average weight reduction at 15 mg. SA prescribing experience appears to track close to this. Some patients exceed the average substantially. Some fall well below. The distribution looks similar to what the trial reported.
What real world data has added is detail on the distribution. The trial reported means and proportions achieving thresholds. Real world data is showing more of the tails. The patients who lose 30 percent or more. The patients who lose almost nothing despite reaching maximum dose. The patients who plateau at 10 percent and stay there.
Why the variation exists is still being studied. Genetic differences in receptor function, individual eating patterns, baseline metabolic profile, and compliance with the lifestyle component all contribute.
Some Real World Patterns Not Highlighted In Trials
Side effect rebound after long stable use
Some patients who have been stable on a maintenance dose for months can experience renewed nausea or gastrointestinal symptoms unexpectedly. The cause is unclear. Often it resolves on its own. Sometimes it indicates an underlying issue (gallbladder, often) that warrants assessment.
Variable response to dose increases
Trial protocols escalated doses on a fixed schedule. Real world practice often slows the schedule based on tolerance, and patients vary widely in how they respond to each step. Some patients see strong effect from 5 mg and need nothing higher. Some need full 15 mg for adequate response. Some plateau at intermediate doses.
The "vacation" question
Some patients want to take temporary breaks from the medication, for surgery, for travel, for events, for various reasons. Real world experience is showing that short breaks (a few weeks) are usually tolerable. Longer breaks essentially restart the conditioning process and effect can be substantially reduced when treatment resumes.
Switching between tirzepatide and semaglutide
Increasingly common in SA practice as patients respond to cost differences or to specific tolerance issues. Real world experience suggests switching is usually manageable. The new medication starts at its lowest dose. The transition usually goes smoothly. Some patients respond better to one than the other in ways that do not seem predictable in advance.
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Start ConsultationWhat The Sales Data Reveals
The IQVIA-tracked sales data that Aspen has cited tells a story not just about commercial success but about clinical use patterns. Mounjaro reached number one selling pharmaceutical in SA in November 2025. By end January 2026 it held 52 percent of the GLP-1 market by value. These numbers reflect not just initiation but continued use.
The implication is that most patients starting tirzepatide are continuing it. The dropout rate, if it were high, would prevent this kind of market dominance. The sales growth reflects both new starters and ongoing prescriptions for existing patients.
The Compounded Market Distortion
One area where real world SA experience has highlighted a problem the trials could not have anticipated: the compounded tirzepatide market. According to industry reports, a substantial proportion of South Africans using "tirzepatide" are using compounded or unregulated copies rather than the branded Aspen-distributed product.
This complicates the real world picture. Adverse events from compounded products may be reported in ways that do not clearly distinguish the source. Apparent treatment failures may reflect dose inaccuracy in compounded products rather than the actual molecule failing.
For patients and prescribers, the practical takeaway is to know which product is being used. Genuine Mounjaro from a SAPC registered pharmacy is the regulated route. The branded product and the compounded versions are not interchangeable in terms of safety or efficacy.
What Is Still Uncertain
Several aspects of long term use are not yet clear from real world data:
- What happens at year three and beyond. The longest trial follow up is around 2 years. Real world experience is now reaching that mark but the longer term picture is still being filled in.
- What the outcomes look like in older adults specifically. SA prescribing has included older adults but the data is not yet systematically analysed.
- Whether dose reduction over time is feasible for some patients. Anecdotal experience suggests some patients can taper to lower maintenance doses after sustained results, but this is not yet systematic.
- How adherence holds up at the 3, 5, and 10 year marks. Too early to tell.
- What the impact of generic semaglutide arrival (expected 2027) will be on tirzepatide use patterns.
The Honest Summary
Eighteen months of real world SA experience has been broadly consistent with the trial picture. The medication does what the trials said it would do. Side effects appear at expected rates. Patients continue using it at higher than typical rates. The cardiovascular safety profile has not produced unexpected signals.
What real world data adds is texture. The variability of individual response is wider than averages suggest. Practical issues (dose timing, side effect management, switching, breaks) play out in ways that trial protocols did not capture. The market dynamics around availability, cost, and competing products affect what patients actually experience.
For patients considering tirzepatide in 2026, the trial data plus real world experience provides a reasonable basis for informed decisions. The medication is well characterised. The unknowns are around long term outcomes and individual variation. Both are addressed by ongoing follow up with the treating doctor over time.