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OSTARINE MK2866 OTR-AC: Fitness information


OTR-AC Elite is the latest release from Augmented Labs, an exclusive and bestselling brand here at Predator Nutrition. The supplement marks a new era in SARMs, taking the much-loved MK-2866 and adding an ester to it. This brings about all the same great benefits of Ostarine with some unique added properties that might just make it a better choice in some scenarios! We delve into those here.

What is Ostarine?

In order to fully understand what OTR-AC is, we must understand Ostarine (MK-2866, no ester).

Ostarine (which is sometimes sold under other names such as MK-2866 or Enobosarm) is a selective androgen receptor modulator (SARM). SARMs are supplements designed to act specifically on androgen receptors, as the name suggests. The benefit of this is that effects will be exhibited in the places the user wants them – muscle and bone, with limited side effects on other parts of the body.

Ostarine is one of the most well-studied and most popular SARMs on the market. At this time, GTx (who have been developing the SARM) has conducted over 8 clinical trials on MK-2866 on about 600 hundred subjects. Since the early 2000s, the discoveries made about Ostarine have led to it being used in bodybuilding.

What is OTR-AC?

OTR-AC, also called MK-2866 Ester, is MK-2866 (Ostarine) which has undergone esterification during chemical synthesis to maximize potency, biodistribution, and half-life. The esterification of anabolic agents results in at least a 10-fold increase in half-life, which means that the active ingredient has the potential to remain bioactive ten times longer. This results in numerous benefits, such as decreased dosing frequency and more stable blood levels.

OTR-AC benefits

In coming years, it is possible that OTR-AC might replace many Ostarine products on the market, due to the differences explained above which appeal to many users.

Maximize muscle growth

Increased bone density

Greater strength and performance

Improved recovery

Leaner and drier look

OTR-AC Cycle

OTR-AC Elite comes in 10mg capsules, with up to 3 capsules daily being the recommended dose. If you are using for the first time or planning to stack OTR-AC with another SARM, we’d suggest using the lowest dose for this cycle and progressing the dose upwards only when progress has absolutely stalled and biofeedback suggests you can.

The longest that it is suggested to run an OTR-AC cycle is 12 weeks, with 8 weeks being perfect to reap the rewards. It is important to give your body adequate time to recover and for hormone levels to return to normal before embarking on your next cycle. Longer cycles might require longer off time, depending on how successful your PCT was.


You can treat stacking OTR-AC Elite as you would any Ostarine supplement. Our first thought is that it goes perfectly with Cardareal and a fat burner for a cutting cycle.

PPAR delta agonists such as Cardarine gw-501516 can increase fatty acid oxidation over glycolysis, meaning that fats, not stored carbohydrates, are used as fuel for exercise. This has downstream benefits on muscular endurance and body composition, hence Cardarine often being considered a fat burner. If weight loss is the goal, Cardarine can stack well with stimulant-based fat burners to increase energy expenditure further and increase your calorie deficit.

Another reason to add Cardareal is that it is non-hormonal and won’t add any stress to health markers, like adding more SARMs to the stack might risk.


While some people would say Ostarine supplements do not require PCT, we would still advise a post-cycle therapy of over-the-counter supplements. The only way to know for sure if testosterone has been suppressed is with blood work (recommended).

To cover your bases, we’d follow your OTR-AC Elite cycle with a PCT of Activate Xtreme. We’d also suggest using Cycle Guard Elite year-round to maintain healthy kidney, liver, and lipid values.


OTR-AC Elite is probably one of the most universally suitable SARMs you can find! From beginner to advanced, standalone or stacking, bulking, or cutting, it can have a place. If you were torn between this and a typical ostarine product like Ostareal, we hope that this article has helped clear up some of the key differences.