Cycling and break schedules
Cycling is not one practice applied uniformly. Each schedule below exists for a specific reason, and understanding the reason is what tells you whether a break can be flexed or not.
The short answer
Cycling requirements differ by compound and by rationale. IGF-1 LR3 requires a mandatory four-week break after each four to six week cycle so receptor sensitivity recovers, with three cycles the conventional maximum. Fenbendazole runs three days on and four days offspecifically to reduce bone marrow suppression risk. BPC-157 and TB-500 are not cycled — they run within a defined protocol window and then stop. Thymosin alpha-1 has no established break requirement.
By compound
Run continuously within a defined window of 2–8 weeks depending on whether the condition is acute or chronic, then stop. No mandatory off-cycle is established. For chronic conditions a reduced maintenance schedule of three times weekly is sometimes continued under veterinary direction.
Loading phase of 1–2 doses weekly for 2–4 weeks, then half dose once weekly for 4–8 weeks, then stop. No withdrawal syndrome has been reported. The limiting factor is not tolerance but the cancer contraindication, which should be revisited if the protocol is extended.
Given 2–3 times weekly for 4–12 weeks, and may be continued long term for chronic conditions under veterinary direction. No cumulative toxicity has been reported and no mandatory break is established — the most forgiving schedule of any compound here.
Injectable use is limited to 4–8 weeks, after which it should be discontinued or transitioned to topical. Topical application carries minimal systemic absorption and may continue indefinitely for chronic dermatologic conditions. Recheck liver values if injectable use exceeds four weeks.
Mandatory four-week off-cycle after every 4–6 week cycle, with a conventional maximum of three cycles. The break allows IGF-1 receptor sensitivity to recover. This is the strictest cycling requirement on the site and is not optional.
Run 4–6 weeks with a taper to every other day over the final two weeks, then discontinue. Must not be run concurrently with IGF-1 LR3 — overlapping receptor pathways.
Run 8–12 weeks or longer with full restaging at week 12. No cycling schedule is established because no companion animal data exists to establish one. Continuation should be governed by quality of life and veterinary oncology assessment.
Three consecutive days on, four days off, repeated weekly for 4–12 weeks or longer. The four-day break is a safety mechanism to allow bone marrow and hepatic recovery, and monthly CBC monitoring accompanies it. Do not compress the schedule.
Either daily or five days on and two days off, for 4–12 weeks or longer, with monthly monitoring. MDR1 testing precedes the first dose. Do not exceed 0.6 mg/kg/day in this context.
Related guides
Common questions
Do peptides need to be cycled in dogs?+
It depends entirely on the compound, and the reasons differ. IGF-1 LR3 requires a mandatory four-week break after each four to six week cycle so receptor sensitivity can recover. Fenbendazole uses a three-days-on, four-days-off weekly schedule specifically to reduce the risk of bone marrow suppression. BPC-157 and TB-500 are run continuously within a defined protocol window and then stopped rather than cycled. Treating all of them the same way misses the point of why any given schedule exists.
Why does IGF-1 LR3 need a mandatory off-cycle?+
Continuous IGF-1 receptor stimulation leads to receptor downregulation, so sustained dosing produces diminishing effect while the risks — particularly hypoglycaemia — persist. A four-week break after each four to six week cycle allows receptor sensitivity to normalise. Three cycles is the conventional maximum.
Why is fenbendazole given three days on and four days off?+
Fenbendazole is approved for a three-day deworming course. The extended schedules used in oncology contexts go well beyond that, and pancytopenia has been documented in dogs on continuous daily dosing. The four-day weekly break exists to allow bone marrow and hepatic recovery. It is a safety mechanism, not an arbitrary rhythm.
What happens if a dose is missed?+
For daily compounds like BPC-157, a single missed dose is not significant — resume the normal schedule rather than doubling up. For weekly compounds like TB-500, give the dose when remembered and reset the weekly interval from that point. Doubling a dose to compensate is never appropriate, particularly with IGF-1 LR3 where the hypoglycaemia risk is dose-dependent.
Educational information — not veterinary medical advice
Everything on this page is compiled from published peer-reviewed literature for educational and research purposes. It does not establish a veterinarian-client-patient relationship (VCPR) and is not a substitute for veterinary examination and diagnosis. Most compounds described here are investigational or used off-label and are not FDA-approved for these purposes in dogs. Extralabel drug use in animals requires a valid VCPR and the direct supervision of a licensed veterinarian under AMDUCA (21 U.S.C. §360b). Dosing figures are reported as they appear in the source literature and are not recommendations.