Intex Pharma Retatrutide Prefilled Pen

What is the Intex Pharma Retatrutide Prefilled Pen?

The Intex Pharma Retatrutide Prefilled Pen delivers Retatrutide (LY3437943), the world’s first triple hormone receptor agonist targeting GLP-1, GIP and glucagon receptors simultaneously. Developed by Eli Lilly, Retatrutide is the most advanced weight loss compound in clinical development. The prefilled pen format allows precise once-weekly subcutaneous dosing without the need for reconstitution, vial handling or dose calculation. Available from the Intex Pharma shop at £155.00 with same day UK despatch.

Retatrutide is the furthest advanced triple agonist in the global obesity drug pipeline. Where Semaglutide targets a single receptor and Tirzepatide targets two, Retatrutide activates three distinct receptor pathways simultaneously, producing greater weight reduction than any currently approved GLP-1 therapy in clinical trials. For users who prefer vial-based dosing and titration flexibility, the Intex Pharma Retatrutide 2mg vial is also available.

How Retatrutide works

Retatrutide is a single peptide molecule conjugated to a fatty diacid moiety that enables its six-day half-life and supports once-weekly subcutaneous administration. It simultaneously activates three distinct receptors, each contributing a different component of its metabolic effect.

What the clinical research shows

The Phase 2 randomised controlled trial published in the New England Journal of Medicine enrolled 338 adults with obesity and no type 2 diabetes. At 48 weeks, participants receiving Retatrutide at 12mg achieved mean weight loss of 24.2% compared to 2.1% for placebo. At 8mg the figure was 22.8%. These are the largest weight reductions ever recorded in a randomised controlled trial of a pharmacological intervention for obesity at this stage of development. Among participants who received the 12mg dose, 100% achieved at least 5% weight loss and 83% achieved at least 15% weight loss. Additionally, 72% of participants who had prediabetes at baseline reverted to normoglycaemia.

Phase 3 results have continued to confirm the efficacy signal. Eli Lilly announced positive topline results from the Phase 3 TRIUMPH-4 trial in December 2025, reporting average weight loss of 71.2 lbs (approximately 32kg) alongside substantial relief from osteoarthritis pain in adults with obesity and knee osteoarthritis. This represents approximately 26 to 28% mean body weight reduction in the Phase 3 population, confirming the Phase 2 signal at larger scale and across different patient populations.

For liver health, the Phase 2a substudy published in Nature Medicine and indexed in NIH PMC found mean relative liver fat reductions of 81.4% at 8mg and 82.4% at 12mg after 48 weeks in participants with metabolic dysfunction-associated steatotic liver disease. These reductions are clinically significant in a condition for which no approved pharmacological treatment existed before the GLP-1 class emerged.

Retatrutide vs Semaglutide vs Tirzepatide

Dosing guide

Retatrutide is injected subcutaneously once weekly. The standard titration protocol from the Phase 2 trial begins at a low dose and escalates gradually to allow the body to adapt to the GLP-1-mediated gastrointestinal effects before moving to higher doses. Starting at the full dose immediately produces more nausea and GI side effects than starting low and titrating upward.

Many users in the UK community achieve their target weight loss at 2mg to 4mg per week without needing to escalate to higher doses, particularly those starting with moderate weight loss goals rather than the significant obesity populations studied in the clinical trials. Starting at 1mg and spending at least four weeks at each dose level before escalating is the approach that produces the best tolerability profile.

Side effects

• Nausea. The most common side effect, particularly during dose escalation. Eating smaller meals, avoiding high-fat foods and not eating immediately before the injection all reduce nausea. It typically resolves within two to four weeks at a stable dose.
• Reduced appetite. This is the intended mechanism rather than a side effect, but the appetite suppression from Retatrutide can be more pronounced than with Semaglutide. Ensuring adequate protein and micronutrient intake during significant appetite suppression is important.
• Vomiting and diarrhoea. More common at higher doses and during rapid escalation. Staying at each dose level for at least four weeks before escalating minimises this.
• Fatigue. Reported during the early weeks of treatment. Usually resolves as the body adapts to the new metabolic state.
• Injection site reactions. Mild redness or bruising at the subcutaneous injection site. Rotating sites and using the pen correctly minimises this.

Retatrutide should not be used by anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN2), in line with the precautionary labelling applied to all GLP-1 receptor agonists.

Frequently asked questions about Intex Pharma Retatrutide Prefilled Pen