Receptor mechanism

7-OH binds the mu-opioid receptor with an affinity roughly 13× that of morphine and 46× that of mitragynine in radioligand studies, but with markedly reduced β-arrestin-2 recruitment (Kruegel 2016; Váradi 2016). In drug-discrimination assays, rats generalise 7-OH to morphine — the parent alkaloid mitragynine does not (Obeng 2021). Translated to effect: the subjective profile of 7-OH sits closer to classical opioids than to kratom leaf, and its partial-agonist character means effects plateau as dose climbs while side-effect risk keeps rising.

Low dose (1–5 mg)

At the low end of the user-reported range, 7-OH produces subtle opioid-typical effects without overt sedation: a mild lift in mood and sociability, a reduction in background anxiety, and slight sharpening of attention rather than the stimulant-like brightening that low-dose kratom leaf produces. Analgesia is modest — enough to take the edge off a background ache but not reliably useful for acute pain. First-time users on the lower half of this range frequently describe the effect as “less than expected,” which is the correct reference point to start from.

Moderate dose (5–15 mg)

The moderate range is where 7-OH’s opioid character becomes unambiguous. Analgesia is reliable, physical relaxation is pronounced, and most users report a warmth-and-contentment euphoria closer to oxycodone than to kratom leaf. Anxiolysis is marked and duration of subjective effect lengthens. Motor and cognitive impairment are usually mild at the bottom of this range and noticeable at the top — driving and safety-critical tasks are not appropriate from the middle of this range onward.

High dose (15 mg+)

Above ~15 mg, the partial-agonist ceiling begins to bend: sedation dominates, analgesia deepens only modestly, and the likelihood of nausea, vomiting, sweating, itching, and cognitive fog rises sharply. Respiratory depression risk remains lower than full mu-agonists at equivalent receptor occupancy, but that margin collapses in combination with alcohol, benzodiazepines, or other CNS depressants — the polydrug pattern seen in most kratom-involved overdose deaths (CDC MMWR 2019). Full adverse-event profile on the side effects page.

Onset and duration by format

No controlled human pharmacokinetic study has been published for isolated 7-OH, but mitragynine PK in chronic kratom users shows a ~24-hour terminal half-life (Trakulsrichai 2015). Subjective timelines converge across user reports and product labelling:

Tablets / capsules — onset 20–45 min, peak 60–90 min, experiential duration 4–6 hours. Solid-dose first-pass metabolism is the slowest route.
Shots / liquids — onset 10–20 min, peak 30–60 min, duration 3–5 hours. Faster absorption, sharper rise.
Sublingual / chewables — onset 10–15 min, peak 30–60 min, duration 3–5 hours. Bypasses first-pass for the fraction that dissolves under the tongue; swallow fraction behaves like a tablet.
Powder in drink — onset 15–30 min, peak 60–90 min, duration 4–6 hours. Dose accuracy is the limiting factor; see the dosage guide for scale requirements.

The experiential tail rarely lasts beyond six hours, but the long PK half-life of the parent kratom alkaloids means residual next-day effects — mild fatigue, affective flatness — are common with daily use.

What moves the dose-response curve

CYP3A4 activity. 7-OH is both delivered and cleared by CYP3A4 (Kruegel 2019; Kamble 2020). Strong inhibitors (ketoconazole, ritonavir, grapefruit juice) raise exposure; inducers (rifampin, carbamazepine, St. John’s wort) lower it. Inter-individual CYP3A4 variation alone can shift effective dose by multiples.
Baseline opioid tolerance. Users with recent kratom extract or pharmaceutical opioid exposure sit higher on the tolerance curve and will under-respond at naive-user doses.
Food and gastric state. Empty-stomach dosing produces faster, steeper onset; a fatty meal can blunt the peak and lengthen the tail. This matters more for tablets than for sublingual formats.
Product quality and label accuracy. 7-OH content in consumer products has been documented to diverge from label claims; without a current COA, “10 mg” on the package is a guess.
Concurrent substances. CNS depressants compound respiratory risk multiplicatively, not additively. This is the single most important moderator of adverse outcomes in the epidemiology (Post 2019).

Tolerance and dependence

Chronic kratom users develop a withdrawal syndrome paralleling classical opioid withdrawal — muscle aches, insomnia, irritability, craving — with severity that tracks cumulative dose and duration of use (Singh 2014). Rats self-administer isolated 7-OH at rates comparable to morphine while ignoring mitragynine (Hemby 2019), which is the best available evidence that concentrated 7-OH products compress the time-to-dependence relative to whole-leaf kratom. Daily users should expect tolerance within weeks and dependence on the timescale of months; see the withdrawal page for management.