What is the difference between the GLP-1RA Medications?
Key Takeaways
GLP-1 RAs are a class of medications that can be used to treat diabetes or to promote weight loss.
They mimic a natural hormone in the body called GLP-1, which helps to keep blood sugar from rising too high as well as slowing the emptying of the stomach and acting in the brain to reduce hunger and food cravings.
There are several different GLP-1 RAs currently approved for use in Singapore.
Most GLP-1 RAs are taken by injection, but there is also an oral option that’s taken as a pill.
Some GLP-1 RAs are taken weekly, while others are taken daily.
All GLP-1 RAs have been shown to be effective, but there are some differences between them.
A medical professional can advise you about which GLP-1 RA they would recommend in your specific case.
| Drug Name | Active Ingredient | Indication | Impact on HbA1c | Impact on weight | Administration | Approved for use in Singapore | Currently available? |
|---|---|---|---|---|---|---|---|
| Mounjaro | tirzepatide | diabetes | decrease of 2.0% | injected | yes | no | |
| Ozempic | semaglutide | diabetes | decrease of 1.6% | injected | yes | yes | |
| Rybelsus | semaglutide | diabetes | decrease of 1.5% | oral | yes | yes | |
| Saxenda | liraglutide | obesity | 5-10% weight loss | injected | yes | yes | |
| Trulicity | dulaglutide | diabetes | decrease of 1.6% | injected | yes | yes | |
| Victoza | liraglutide | diabetes | decrease of 1.5% | injected | yes | yes | |
| Wegovy | semaglutide | obesity | 15% weight loss | injected | yes | no | |
| Zepbound | tirzepatide | obesity | 26% weight loss | injected | no | no |
What are GLP-1 RAs?
Glucagon-like peptide-1 receptor agonists, or GLP-1 RAs, are medications that mimic a natural hormone in the body known as GLP-1. This hormone is released after meals. It helps to keep blood sugar from rising too high, and it also helps to keep you feeling full for a while after a meal.
Some GLP-1 RAs are approved for treating diabetes, while others are approved for weight loss. Although the general way that the medications work is the same for all GLP-1 RAs, different specific medications differ from each other in various ways.
GLP-1 RAs are prescription medications. This means that you can’t buy them yourself over the counter – they’re only available with a doctor’s prescription. If you’d like to consider taking a GLP-1 RA, you’ll need to schedule a consultation with a doctor. After an assessment and a discussion of your medical history, they’ll be able to determine whether GLP-1 RAs are likely to be safe and effective for you. If so, then they’ll dispense the medication. They’ll also continue to have follow-up appointments with you to ensure that everything is going well, and may make changes (such as adjustments to your dosage) as needed.
Availability and Uses
Currently, the GLP-1 RAs that are approved in Singapore include:
Mounjaro (tirzepatide) for treating diabetes
Ozempic (semaglutide) for treating diabetes
Rybelsus (semaglutide) for treating diabetes
Saxenda (liraglutide) for weight loss
Trulicity (dulaglutide) for treating diabetes
Victoza (liraglutide) for treating diabetes
Wegovy (semaglutide) for weight loss
Zepbound, a form of tirzepatide that’s approved in the US for weight loss, is not currently approved in Singapore.
Dosages
Most GLP-1 RAs are given by injection, although there’s one option that’s taken orally as a pill. These medications come in the form of pens, which are designed for easy self-injection at home. If you start taking a GLP-1 RA, your medical team will ensure that you learn how to do this.
Ozempic is given as a weekly injection.
Rybelsus is given as a daily pill.
Wegovy is given as a weekly injection.
Saxenda is given as a daily injection.
Victoza is given as a daily injection.
Trulicity is given as a weekly injection.
Mounjaro is given as a weekly injection.
Although some people prefer taking a pill over giving themselves an injection, it’s important to carefully consider what this requires. In order for semaglutide to be absorbed in the digestive tract, it must be taken on an empty stomach, with only a minimum amount of water and without any other medications or anything else in the stomach. If semaglutide is taken with anything else, or even with too much water, this significantly reduces the absorption, and the medication may not be effective.
Most people take it first thing in the morning, and then wait half an hour to an hour before taking anything else at all. Although this works well for some people, others find it to be inconvenient, because they prefer to take coffee, tea, or breakfast soon after awakening. A daily or weekly injection may be more convenient in this case.
However, taking an injection can also be less convenient, particularly in certain situations (such as while traveling). Pills may be an easier option for those who travel frequently. In addition, some people have a phobia of needles, or simply don’t like them. They may prefer taking pills in order to avoid needing to give themselves an injection. Which option is better depends on the individual’s lifestyle and preferences.
Differences between the active ingredients
Semaglutide, liraglutide, and dulaglutide are all GLP-1 RAs, and they all work in a similar way, by mimicking GLP-1. However, there are some differences between them.
Liraglutide has a much shorter half life, meaning that the body removes it much faster. After taking a dose of liraglutide, half of it has been cleared from the body within 13 to 15 hours.
By contrast, it takes 165 hours – about a week – to clear half of a dose of semaglutide from the body. For dulaglutide, it’s about 90 hours. This is why liraglutide needs to be taken daily, while semaglutide and dulaglutide can be taken weekly.
Tirzepatide is also a GLP-1 RA, but it works a little bit differently. Besides the GLP-1 receptor, it also activates the receptor for another hormone known as glucose-dependent insulinotropic polypeptide, or GIP. Similar to GLP-1, this hormone also reduces appetite and helps to keep blood sugar from rising too high, and it also improves insulin sensitivity. Tirzepatide acts on the systems for both of these hormones, instead of solely acting on the GLP-1 receptor as other GLP-1 RAs do.
Effectiveness
All GLP-1 RAs have been shown to be effective for controlling diabetes or for weight loss. However, there have been some differences found in terms of results.
It’s important to note that medications affect different people in different ways. Studies can only reveal the average effects of medications, but each individual’s body may be different from the average. This is why there’s no one “best” GLP-1 RA. A medical professional can talk with you about which specific GLP-1 RA they recommend, based on factors like your medical history. You may also need to try more than one medication to determine which one works best for you.
In studies of the GLP-1 RAs that are currently approved in Singapore for weight loss:
Semaglutide resulted in weight loss of about 15% of the person’s starting body weight.
Liraglutide resulted in weight loss of 5-10% of the person’s starting body weight.
In studies of tirzepatide, it appears that it may be more effective for weight loss than other GLP-1 RAs. Recent studies have found that tirzepatide results in weight loss of more than 26% of body weight. However, tirzepatide is not currently approved for weight loss in Singapore, but is only approved for treating diabetes.
In studies of the GLP-1 RAs that are currently approved in Singapore for treating diabetes, the average decrease in HbA1c is approximately:
A few studies have directly compared the effects of the various GLP-1 RAs on glycemic control. Some studies have shown that semaglutide lowers HbA1c more than dulaglutide does, while tirzepatide appears to lower it more than semaglutide does. Other studies have shown that liraglutide and dulaglutide are approximately equal in effectiveness. In general, higher doses of GLP-1 RAs are more effective at controlling blood sugar than lower doses are, although they also cause more side effects.
Side Effects
In general, the side effects of GLP-1 RAs are similar across the whole class of medications. The most common side effects are:
Nausea and vomiting
Abdominal pain and bloating
Indigestion or acid reflux (heartburn)
Constipation or diarrhea
Weakness during exercise
Headache
These side effects are dose-dependent, and tend to occur when the dose is increased. After the body gets used to the new dose of the medication, the side effects will tend to diminish. There are also lifestyle changes that can help to reduce the side effects, such as taking smaller meals, avoiding oily or fatty meals, avoiding lying down after meals, taking a snack before exercising, and taking plenty of fluids.
There are some uncommon side effects that may be associated with specific GLP-1 RAs. For example, it’s important to use caution with dulaglutide for people with an arrhythmia (abnormal heart rhythm), because there are some reports of it interfering with electrical conduction in the heart. Liraglutide and injectable semaglutide might also be more likely to cause gallbladder issues than dulaglutide or oral semaglutide are. However, this is a rare side effect, and it’s still uncertain whether the small increase in gallbladder issues is actually caused by GLP-1 RAs or by weight loss itself (which is known to increase the risk of gallbladder issues).
Seek the advice of a medical professional
Because they’re prescription medications, a doctor’s prescription is needed to get access to a GLP-1 RA. If you believe that one of these medications might benefit you, you should make an appointment with a medical professional to discuss it. After a thorough consultation and a discussion of your medical history, they’ll advise you about whether they recommend a GLP-1 RA for you, and if so, which one.
GLP-1 RAs work best when used in combination with healthy lifestyle changes, like exercise and a healthy diet. They’re not a substitute for these factors, but a way to supplement them. Creating and maintaining a healthy lifestyle plan can be challenging for many people, and it’s helpful to have support. This is why clients in our NOVI Health medical weight loss program, NOVI Optimum Plus, receive support from health coaches, to help them succeed in their weight loss journeys.