SYNAPSE Blend Side Effects: Semax, Selank, MOTS-c and Tesamorelin, and What to Report

Only the tesamorelin rows have percentages behind them, from the approved product's label. The rest are clinical reports, because there is no trial of the blend.

The medication this page covers:

At 0.25 mL, each dose is 0.25 mg Semax, 0.25 mg Selank, 0.5 mg MOTS-c and 0.5 mg tesamorelin (arithmetic from the vial strengths, on a U-100 insulin syringe). Your own directions are set by your physician after reviewing your intake and are printed on the vial. The price is all-in: medication, physician review, refill management and shipping, with no membership fee.

SYNAPSE is four peptides in one vial, and every safety question about it is four questions about its parts.

Clinical reports on the blend are consistent with those: mostly injection-site reactions, with some people describing early nausea or light-headedness. The gaps matter as much as the findings: the Semax and Selank human work was intranasal, MOTS-c has never been given to people in a controlled trial, and nobody has followed people on the four together for months. Component detail is in tesamorelin side effects, MOTS-c side effects, Semax side effects and Selank side effects.

Tesamorelin prompts a pulse of your own growth hormone, which works largely through IGF-1 made in the liver. Almost every side effect on its label is that mechanism: growth hormone makes the body hold more fluid, which shows up as puffiness, joint aches, swelling and tingling, and it reduces insulin sensitivity, which is the reason for the blood sugar warning.

These rates come from the approved product's label, which pools data from 740 treated patients, 543 of them in the 26-week placebo-controlled phase. They were recorded at 2 mg daily in adults with HIV; SYNAPSE delivers 0.5 mg on weekdays, but the mechanism is the same, so the label is the reference point. Read the placebo column too: 11% of people on a dummy injection reported joint pain. In the 2012 cognition trial in older adults, at 1 mg nightly, adverse events were mild but more frequent on the drug, 68% against 36%.

The approved products also carry warnings for increased risk of neoplasms and elevated IGF-1, are contraindicated in active malignancy, in disruption of the hypothalamic-pituitary axis, in pregnancy and in known hypersensitivity, and note that long-term cardiovascular safety has not been established. Tesamorelin's label also notes that growth hormone can alter the metabolism of drugs cleared by cytochrome P450 enzymes and that people on corticosteroid replacement may need dose adjustment.

The blood sugar caution

This is the side effect that needs the most attention, and two components pull in different directions. Tesamorelin can raise blood sugar. MOTS-c is described in mouse work improving insulin sensitivity. Nobody has studied what the two do together.

In practice: diabetes or borderline glucose goes on the intake. Thirst or frequent urination is a reason to message your care team. Anyone on glucose-lowering medication, including a GLP-1, should know the signs of low blood sugar, shakiness, sweating or confusion, treat it, and report it. Do not change any medication dose yourself.

Because MOTS-c acts on an energy-sensing pathway, AMPK, the one exercise switches on, some people describe transient jitteriness, a faster pulse or mild light-headedness in the hour or two after a dose, particularly early in a course. It usually settles. A heart that races at rest, or light-headedness that does not pass, is a reason to message your care team. MOTS-c has no human safety data, which is exactly what the FDA's reviewers pointed to in July 2026.

Restlessness. Some people describe transient restlessness or feeling over-alert if Semax is taken late in the day. If it affects your sleep, message your care team about timing rather than moving the dose yourself.

Early fatigue, or the opposite. Selank is sometimes described as causing early fatigue or a flat, low-drive feeling in the first days, and a small number of people describe feeling wired. Both are usually described as settling.

What is not expected. Semax is described as devoid of the corticotropic activity of ACTH, so it is not expected to raise cortisol, and it is not a stimulant. Selank is described in the Russian literature as acting without the sedation, memory impairment and dependence associated with benzodiazepines.

Psychiatric medications and stimulants

There is no established interaction list for SYNAPSE or any component, because the trials that would produce one have not been run.

Anyone on existing psychiatric treatment should have it reviewed by the prescriber before adding anything that modifies GABA signalling. Do not stop any prescribed medication to start SYNAPSE.

The most frequent report. A small red, itchy or tender area that fades within a day or two is expected. A site that is larger, hotter or more painful at 48 hours than at 24 is behaving like an infection and should be looked at the same day. Rotating sites between abdomen and thigh, letting the alcohol dry and using a fresh syringe every time reduce how often reactions happen. Technique is in how to inject peptides safely.

If you think you may have taken too much, for example by drawing the wrong amount, call Poison Control at 1-800-222-1222 and message your care team. Do not skip, double or change a dose to compensate.

Not every side effect is urgent. Message your care team through your account for:

• Injection-site reactions that keep happening despite rotating sites.
• Joint aches, puffiness or tingling that has not settled.
• Jitteriness, restlessness, poor sleep, tiredness or headache that has not settled after the first couple of weeks.
• Any change in your medications, especially diabetes medication, a GLP-1, psychiatric medication or a stimulant.
• A new diagnosis, a pregnancy, or a planned surgery.
• A vial that looks different from the last one.

Your physician may revise your directions, change the product, or stop treatment. Do not change the dose yourself. When directions change, the new numbers are printed on the new label. The conversions are in SYNAPSE blend dosage.

Bloodwork is not required for any Pepti treatment. If your physician wants labs for your care, they'll ask through your account.

• Side effects of the four together. SYNAPSE has never been studied as a combination.
• MOTS-c in people. There are no human trials; its side effects are clinical reports.
• Semax and Selank by injection. Their human work was intranasal.
• What tesamorelin and MOTS-c do to glucose together. They are described pulling in opposite directions, and nobody has measured the combination.
• Long-term outcomes. No cohort has been followed for years on SYNAPSE, and the approved tesamorelin label says the effects of prolonged IGF-1 elevation are unknown.

Tesamorelin is the component with a formal safety profile, because it has a label built from placebo-controlled trials, and its effects are predictable from its mechanism and dose-related. The other three are generally described as well tolerated in their own work, and clinical reports on the blend are consistent with that. MOTS-c's absence of human data is an absence, not reassurance. The separate and non-theoretical risk is supply: research-use-only multi-peptide vials are sold with no pharmacy accountable for what is in them. See research peptides vs prescription peptides.

Where the components stand with the FDA: tesamorelin is an approved active ingredient, but compounded tesamorelin is not the approved product; Semax and MOTS-c were recommended for the 503A Bulks List by the advisory committee in July 2026, with the final determinations pending; Selank's nomination was withdrawn and it has never been reviewed. SYNAPSE is not an FDA-approved drug.

SYNAPSE cannot be bought legitimately without a prescription. The prescription route:

1. Complete a free online intake covering your history, medications and what you want help with.
2. A physician licensed in your state reviews it, usually within 24 hours.
3. If it is appropriate, a PCAB-accredited, FDA-registered US 503A compounding pharmacy prepares it to that prescription. Lot test results are published at /quality/lab-results.
4. It ships refrigerated with ice packs, with sterile syringes, alcohol prep pads and your directions printed on the vial.
5. Your physician stays reachable for questions and side effects.

SYNAPSE is $279 a month, all-in, covering medication, physician review, refill management and shipping, with no separate membership fee. Pepti is cash-pay and does not bill insurance. Refills run every 28 days, one vial per fill.