# PT-141 Dosage in the Research Literature

> PT-141 dosage: the 1.75 mg subcutaneous label dose, the Phase 2b dose-ranging arms, the historical intranasal range, plasma half-life and duration of effect. A citation-explicit reading of the dosing record.

The 1.75 mg subcutaneous label dose, the Phase 2b dose-ranging arms, the discontinued intranasal range, the rat-model preclinical doses — read against the published pharmacokinetic record.

## Dose used in clinical trials

PT-141 dosage in the approved indication is `1.75 mg subcutaneous` bremelanotide, administered as a single-use prefilled autoinjector on an as-needed basis [4][7]. The dose was selected from a Phase 2b dose-ranging program that tested 0.75, 1.25, and 1.75 mg subcutaneous arms in premenopausal women with HSDD/FSAD; both 1.25 mg and 1.75 mg met efficacy endpoints with acceptable tolerability, and 1.75 mg advanced to the pivotal Phase 3 program [8].

Historical intranasal trials in male erectile dysfunction used a 7.5-10 mg intranasal range; that formulation program was halted by the FDA in 2007 over a blood-pressure signal [9][4]. Preclinical rat solicitation studies used `0.1-1.0 mg/kg SC` [10]. No daily chronic dosing regimen has been approved or systematically studied at clinical scale.

## Subcutaneous PT-141 injection in trials

The approved subcutaneous PT-141 injection is administered into the abdomen or thigh via the single-use prefilled autoinjector specified by the label [4][7]. The autoinjector delivers a fixed 1.75 mg dose. The product is shipped at room temperature per the storage section of the prescribing information [7].

The trial-confirmed pharmacokinetics support the label timing. Median Tmax of approximately `1.0 hour` (range 0.5-1.0 h) after subcutaneous administration, mean Cmax `72.8 ng/mL`, AUC `276 h*ng/mL`, absolute SC bioavailability approximately 100% [4]. Plasma concentrations increase less than dose-proportionally above approximately 7.5 mg SC.

## Subcutaneous injection sites in trials

The label specifies subcutaneous administration into the abdomen or the thigh [4][7]. Trial protocols used the same anatomical sites.

## Duration of effect and PT-141 half-life

How long does PT-141 last? Plasma half-life after subcutaneous dosing has been reported in the approximately `1.9-4 hour` range across pharmacokinetic submissions [4]. The label-defined dosing window directs administration at least 45 minutes before anticipated activity, with subjective effect duration reported by trial subjects extending several hours post-dose [4][7][17]. The 2022 JCI fMRI study documented self-reported sexual desire elevation persisting up to 24 hours after a single 1.75 mg SC dose in premenopausal HSDD women, though the imaging-detectable cerebellar / SMA modulation was characterized in the acute post-dose window [17].

## PT-141 half-life

PT-141 half-life is approximately `1.9-4 hours` in plasma following subcutaneous administration, with Tmax around `1.0 hour` [4]. The molecule is metabolized by hydrolysis of amide bonds via cellular peptidases, contributing to the absence of significant cytochrome-mediated drug-drug interactions [15].

## Onset of effect

The Vyleesi label directs administration at least 45 minutes before anticipated sexual activity, calibrated to the pharmacokinetic profile of subcutaneous bremelanotide: median Tmax ~1.0-1.5 hours and rapid absorption following autoinjector delivery [4][7]. Subjective onset reported in trial populations aligns with this window.

## Dosing frequency in trials

Can PT-141 be used every day? The approved label caps use at no more than one dose per 24 hours and no more than eight doses per month [4][7]. Trial protocols did not study daily chronic dosing in the SC era. Daily dosing was, however, examined in pharmacokinetic and safety substudies — eight consecutive days of 1.75 mg SC dosing produced a mean 24-hour ambulatory systolic blood pressure increase of approximately `1.9 mmHg` with a transient peak `+2.8 mmHg` at 4-8 hours post-dose, returning to baseline by 8-10 hours [4][19]. The frequency cap on the approved label reflects both the per-occasion indication and the dose-frequency-dependent rise in adverse events.

> Vyleesi label. No more than one dose per 24 hours. No more than eight doses per month.

## Timing of dose

Label-defined timing: at least 45 minutes before anticipated sexual activity, no more than one dose per 24 hours, no more than eight doses per month, administered subcutaneously into the abdomen or thigh via the single-use autoinjector [4][7].

## Reconstitution in research literature

Research-grade PT-141 vials are typically supplied lyophilized; published trial protocols reconstituted in bacteriostatic water or saline. The approved product ships as a prefilled autoinjector — no reconstitution is required for the FDA-approved formulation [7].

> Research-grade PT-141 is not the FDA-approved product and is not interchangeable with it. The approved subcutaneous autoinjector and research-grade lyophilized peptide are distinct items in distinct supply chains, regulated differently.

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A typographic dossier on the bremelanotide literature — RECONNECT, the Vyleesi label, the independent re-analysis — set in one geometric sans, sold to no one.