Misoprostol

證據等級: L5

預測適應症: 2 個

Misoprostol: From Gastric Ulcer & Obstetric Use to Amenorrhea

One-Sentence Summary

Misoprostol is a synthetic prostaglandin E1 (PGE1) analogue with established use in gastric ulcer prevention, medical abortion (combined with mifepristone), cervical ripening, and postpartum haemorrhage management. The TxGNN model predicts it may have potential benefit for Amenorrhea, with 0 registered clinical trials and 7 publications available — though these studies address abortion and retained products of conception rather than amenorrhea as a direct therapeutic target. Evidence is currently classified as L4 (mechanistic/indirect), and no standalone misoprostol product holds a DIN in Canada.

Quick Overview

Item	Content
Original Indication	Not registered in Canada (no DIN on record); known internationally for gastric ulcer prevention and obstetric indications
Predicted New Indication	Amenorrhea
TxGNN Prediction Score	99.64%
Evidence Level	L4
Canada Market Status	Not marketed (0 DINs)
Number of DINs	0
Recommended Decision	Hold

Why Is This Prediction Reasonable?

Misoprostol acts as a synthetic PGE1 analogue that binds prostaglandin EP receptors on uterine smooth muscle, triggering myometrial contractions and promoting cervical softening and dilation. This uterotonic mechanism is biologically relevant to certain subtypes of secondary amenorrhea: when menstruation fails to resume because of retained uterine contents (incomplete miscarriage, missed abortion) or mild intrauterine adhesions (early Asherman’s syndrome), misoprostol’s ability to stimulate contractions and mechanically open the uterine cavity could theoretically restore cyclical bleeding. The BMJ case series (PMID 1486304) and the body of missed-abortion literature offer indirect support for this pathway.

However, amenorrhea is not a single disease. Misoprostol’s mechanism would only be plausible for etiology-specific cases — retained-tissue or mild-adhesion types of secondary amenorrhea — and would have no rationale for amenorrhea driven by hypothalamic-pituitary dysfunction, premature ovarian insufficiency, polycystic ovary syndrome, or other endocrine causes. This etiological heterogeneity sharply limits the scope of any potential repurposing claim.

The available literature does not treat amenorrhea as a therapeutic endpoint. Instead, amenorrhea duration is used as a gestational dating criterion for enrolling participants in medical abortion trials (e.g., “amenorrhea ≤35 days”). There is no study in which restoring menstruation in an amenorrhoeic patient was the primary outcome. This gap — high TxGNN mechanistic score, zero direct clinical evidence — explains the L4 classification and the Hold recommendation.

Clinical Trial Evidence

Currently no related clinical trials registered for misoprostol in amenorrhea.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
25394644	2015	RCT	Reproductive Sciences	Dose-ranging RCT (n=2,500); mifepristone 50–150 mg + misoprostol 200 µg for ultra-early pregnancy termination; amenorrhea ≤35 days used as eligibility criterion, not a treatment endpoint
27678099	2017	RCT	Reproductive Sciences	RCT (n=744); low-dose mifepristone + self-administered misoprostol for ultra-early medical abortion; demonstrates comparable efficacy between hospital and home administration
29974571	2018	RCT	J Obstet Gynaecol Res	RCT on self-administered low-dose mifepristone + misoprostol for early pregnancy termination; evaluates safety and tolerability of home protocols
26405260	2015	Prospective Observational	Human Reproduction	Prospective study of mifepristone + misoprostol given before expected menstruation to prevent unintended pregnancy; amenorrhea used for gestational dating
1486304	1992	Case Series	BMJ	Foundational report on misoprostol for medical management of missed abortion and anembryonic pregnancy; earliest evidence for uterotonic application in retained intrauterine contents — the subtype most relevant to the amenorrhea hypothesis
26001691	2015	Review	JOGC	Canadian Society of Obstetrics & Gynaecology guideline on endometrial ablation for abnormal uterine bleeding; misoprostol cited as a cervical priming agent prior to procedures, not as a treatment for amenorrhea
37113350	2023	Case Report	Cureus	Case report of acute fatty liver of pregnancy with HELLP syndrome; amenorrhea appears as a presenting complaint in context of unrecognised pregnancy, unrelated to misoprostol use

Canada Market Information

No DINs are registered for misoprostol as a standalone product in this dataset.

Note: Misoprostol is available in Canada as a component of Mifegymiso® (mifepristone 200 mg + misoprostol 200 µg), approved by Health Canada for medical termination of intrauterine pregnancy up to 63 days gestational age. Historical standalone misoprostol products (Cytotec®) may warrant a direct search of the current Health Canada Drug Product Database to confirm current market status.

Safety Considerations

Safety data (warnings, contraindications, drug–drug interactions) is not available in this Evidence Pack.

Please refer to the Health Canada product monograph and package insert for complete safety information.

Conclusion and Next Steps

Decision: Hold

Rationale: Despite a high TxGNN prediction score (99.64%), the mechanistic link between misoprostol and amenorrhea is etiology-dependent and indirect — all available literature uses amenorrhea only as a gestational dating criterion in abortion trials, not as a treatment target. Zero registered clinical trials exist for this indication, and the safety profile required for a formal repurposing assessment is currently unavailable (Blocking data gap: TFDA/Health Canada package insert).

To proceed, the following is needed:

Resolve Blocking data gap (DG001): Retrieve Health Canada product monograph for misoprostol/Mifegymiso to complete the S1 safety screen (contraindications, warnings)
Resolve High data gap (DG002): Query DrugBank API for full MOA details — receptor subtype specificity (EP1–EP4), uterine vs. vascular selectivity, and duration of action
Etiology-specific evidence search: Narrow the research question to secondary amenorrhea due to retained products of conception or intrauterine adhesions; search for misoprostol use in Asherman’s syndrome management as an adjunct post-adhesiolysis
Differentiate from alprostadil: Clarify and document the distinction between misoprostol (oral/vaginal PGE1 analogue) and alprostadil (IV PGE1) to ensure the second-ranked prediction (atypical coarctation of aorta, L5/Hold) is not conflating the two agents in the knowledge graph
Standalone DIN verification: Confirm current Health Canada Drug Product Database status for misoprostol as a standalone product before any regulatory pathway analysis
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.