AOD-9604 and SNRIs (Venlafaxine, Duloxetine): Interaction Guide

What is AOD-9604?

AOD-9604 is amino acids 177 to 191 of human growth hormone with an extra tyrosine at the N-terminus, which is why it is also sold as hGH fragment 176-191 [4]. It is not full-length growth hormone and not an FDA-approved drug; it went into phase IIa trials as an obesity candidate by February 2002 [6]. A 2026 review reports that a 24-week study of an oral AOD-9604 candidate (534 enrolled, 502 randomized) failed to show a significant benefit on its primary weight-loss endpoint, and notes that this rests on sponsor-reported phase 2 results rather than peer-reviewed randomized trials [1].

What do the SNRI labels say about blood pressure?

The Effexor XR label says to control pre-existing hypertension before treatment, monitor blood pressure regularly, and consider dose reduction or discontinuation if blood pressure stays elevated [2]. Sustained hypertension (supine diastolic at least 90 mm Hg and at least 10 mm Hg above baseline on three visits) occurred in 19 of 705 patients with major depression, about 3%, at 75 to 375 mg a day, and in 0.5% to 0.9% in the other labeled indications [2]. For duloxetine, adult placebo-controlled trials showed a mean systolic rise of 0.5 mm Hg and diastolic rise of 0.8 mm Hg, against falls of 0.6 and 0.3 mm Hg on placebo; the label still says to check blood pressure before and periodically [5].

Does either drug carry a serotonin syndrome warning?

The Effexor XR label states that SNRIs, including venlafaxine, can precipitate serotonin syndrome, that the risk rises with other serotonergic drugs and with MAOIs, and that it can also occur with the SNRI alone [2].

Could one drug change the other's blood level?

Venlafaxine depends on CYP2D6 to form its active metabolite O-desmethylvenlafaxine, and duloxetine is cleared by CYP1A2 and CYP2D6 and is a moderate CYP2D6 inhibitor [2][5]. The published laboratory work on AOD-9604 incubated it in serum and urine and identified six potential metabolites, one of them more stable than the parent peptide [4]. Because AOD-9604 has no approved label, there is no label guidance on how it might combine with these drugs.

What does the venlafaxine label say about weight-loss agents?

The Effexor XR label says combining venlafaxine with weight-loss agents is not recommended, and that the safety and efficacy of venlafaxine with weight-loss agents, including phentermine, have not been established [2]. The label does not name AOD-9604.

Regulatory status of AOD-9604

AOD-9604 is not FDA-approved and has no approved dose [1]. FDA lists it in its table of bulk substances nominated for compounding but withdrawn. It cites potential immunogenicity risk for certain routes of administration, no or only limited safety information, and serious adverse events that may be associated with it though causality is not clear [3]. Removal from category 2 was not a finding that it is safe [3].