Peptide Drug Interactions — Complete Reference

Complete Peptide Drug Interactions Reference

A comprehensive, structured database of 100+ known interactions between peptides and conventional drugs, organized by peptide class.

Severity Classification

Severity	Meaning	Action Required
Major	Avoid combination; significant risk of harm	Contraindicated or switch
Moderate	Use with caution; may require dose adjustment	Monitor, adjust, or consider alternatives
Minor	Low clinical significance; monitor	No dose change typically needed

Mechanism Classification

Mechanism	Description
PK — Absorption	Altered GI absorption (delayed, enhanced, reduced)
PK — Distribution	Protein binding displacement, altered Vd
PK — Metabolism	CYP450 induction/inhibition, peptidase effects
PK — Excretion	Renal/hepatic clearance alterations
PD — Synergistic	Additive or enhanced pharmacological effect
PD — Antagonistic	Opposing pharmacological effects
PD — Additive toxicity	Overlapping adverse effects
Formulation	Physical/chemical incompatibility

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GLP-1 Receptor Agonists

Semaglutide

Drug	Severity	Mechanism	Effect	Recommendation
Insulin glargine	Moderate	PD — Synergistic	↑Hypoglycemia risk	↓Insulin dose 25%
Insulin degludec	Moderate	PD — Synergistic	↑Hypoglycemia risk	↓Insulin dose 25%
Insulin lispro	Moderate	PD — Synergistic	↑Hypoglycemia risk	↓Bolus dose 25%
Warfarin	Minor	PK — Metabolism	INR may fluctuate	Monitor INR closely
Levothyroxine	Minor	PK — Absorption	Delayed T4 absorption	Separate dosing by 4h
Oral contraceptives	Minor	PK — Absorption	Delayed EE absorption	Use barrier method
Metformin	Minor	PD — Additive	GI effects additive	Take with food
GLP-1 RAs (other)	Minor	PD — Additive	GI side effects	Avoid combination
Sulfonureas	Moderate	PD — Synergistic	↑Hypoglycemia	↓Sulfonylurea dose
SGLT2 inhibitors	Minor	PD — Additive	Volume depletion risk	Monitor renal function
Statins	Minor	PK — Absorption	Minor PK interaction	No adjustment needed
Antihypertensives	Minor	PD — Additive	↓BP (rare)	Monitor
Anticoagulants (DOACs)	Minor	PK — Metabolism	Minor PK interaction	Monitor bleeding
Corticosteroids	Minor	PD — Antagonistic	↑Blood glucose	Monitor glucose
Lithium	Minor	PK — Absorption	Delayed absorption	Monitor lithium levels
Digoxin	Minor	PK — Absorption	Delayed absorption	Monitor digoxin levels

Liraglutide

Drug	Severity	Mechanism	Effect	Recommendation
Insulin glargine	Moderate	PD — Synergistic	↑Hypoglycemia risk	↓Insulin dose 20%
Warfarin	Minor	PK — Metabolism	INR fluctuation	Monitor INR
Levothyroxine	Minor	PK — Absorption	Delayed absorption	Separate by 4h
Oral contraceptives	Minor	PK — Absorption	Delayed EE absorption	Barrier method
Sulfonureas	Moderate	PD — Synergistic	↑Hypoglycemia	↓SU dose 50%
Metformin	Minor	PD — Additive	GI effects	Take with food

Dulaglutide

Drug	Severity	Mechanism	Effect	Recommendation
Insulin glargine	Moderate	PD — Synergistic	↑Hypoglycemia risk	↓Insulin dose 20%
Warfarin	Minor	PK — Metabolism	INR fluctuation	Monitor INR
Sulfonureas	Moderate	PD — Synergistic	↑Hypoglycemia	↓SU dose 50%

Exenatide

Drug	Severity	Mechanism	Effect	Recommendation
Metformin	Minor	PD — Additive	GI effects	Take with food
Insulin glargine	Moderate	PD — Synergistic	↑Hypoglycemia	↓Insulin dose
Warfarin	Minor	PK — Metabolism	INR fluctuation	Monitor INR
Acetaminophen	Minor	PK — Absorption	Delayed Tmax	No clinical effect
Digoxin	Minor	PK — Absorption	↓Digoxin exposure	Monitor levels

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Dual GIP/GLP-1 Agonists

Tirzepatide

Drug	Severity	Mechanism	Effect	Recommendation
Insulin glargine	Moderate	PD — Synergistic	↑Hypoglycemia risk	↓Insulin dose 25%
Insulin degludec	Moderate	PD — Synergistic	↑Hypoglycemia risk	↓Insulin dose 25%
Warfarin	Minor	PK — Metabolism	INR fluctuation	Monitor INR
Oral contraceptives	Minor	PK — Absorption	Delayed absorption	Barrier method
Metformin	Minor	PD — Additive	GI effects	Take with food
Sulfonureas	Moderate	PD — Synergistic	↑Hypoglycemia	↓SU dose 50%

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Growth Hormone Secretagogues

CJC-1295 DAC

Drug	Severity	Mechanism	Effect	Recommendation
Insulin	Moderate	PD — Synergistic	↑Hypoglycemia	Monitor glucose
Oral hypoglycemics	Moderate	PD — Synergistic	↑Hypoglycemia	Monitor glucose
Corticosteroids	Minor	PD — Antagonistic	↓GH response	Monitor IGF-1
Thyroid hormones	Minor	PD — Additive	↑Metabolic rate	Monitor thyroid
GHRP-6/Ipamorelin	Minor	PD — Synergistic	↑GH release	Monitor IGF-1

Ipamorelin

Drug	Severity	Mechanism	Effect	Recommendation
Insulin	Moderate	PD — Synergistic	↑Hypoglycemia	Monitor glucose
Corticosteroids	Minor	PD — Antagonistic	↓GH response	Monitor IGF-1
Somatostatin analogues	Moderate	PD — Antagonistic	↓GH response	Avoid combination
Dopamine agonists	Minor	PD — Synergistic	↑GH release	Monitor levels

GHRP-6

Drug	Severity	Mechanism	Effect	Recommendation
Insulin	Moderate	PD — Synergistic	↑Hypoglycemia	Monitor glucose
Dopamine agonists	Minor	PD — Synergistic	↑GH release	Monitor levels
Somatostatin analogues	Moderate	PD — Antagonistic	↓GH response	Avoid combination
Glucocorticoids	Minor	PD — Antagonistic	↓GH response	Monitor

MK-677

Drug	Severity	Mechanism	Effect	Recommendation
Insulin	Moderate	PD — Synergistic	↑Insulin resistance	Monitor glucose
Oral hypoglycemics	Moderate	PD — Additive	Glucose fluctuation	Monitor glucose
Corticosteroids	Minor	PD — Additive	↑Cortisol additive	Monitor cortisol
Warfarin	Minor	PK — Metabolism	INR fluctuation	Monitor INR
CYP3A4 inhibitors	Minor	PK — Metabolism	↑MK-677 levels	Monitor

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Oxytocin and Vasopressin Analogues

Oxytocin

Drug	Severity	Mechanism	Effect	Recommendation
Ergot alkaloids	Major	PD — Additive toxicity	↑↑Hypertension	Contraindicated
Prostaglandins	Moderate	PD — Synergistic	↑Uterine stimulation	Monitor
Cyclopropane	Major	PD — Additive	↑Hypotension, arrhythmia	Avoid
V2 agonists	Moderate	PD — Synergistic	Water intoxication risk	Monitor sodium
MAO inhibitors	Minor	PK — Metabolism	↑Oxytocin effect	Monitor
SSRIs	Minor	PD — Additive	↑Serotonin syndrome risk	Rare

Desmopressin

Drug	Severity	Mechanism	Effect	Recommendation
Lithium	Major	PD — Antagonistic	Water intoxication	Contraindicated
NSAIDs	Minor	PD — Synergistic	↑Antidiuretic effect	Monitor
Carbamazepine	Minor	PD — Synergistic	↑Hyponatremia risk	Monitor sodium
Chlorpropamide	Minor	PD — Synergistic	↑Antidiuretic effect	Monitor
Demeclocycline	Minor	PD — Antagonistic	↓Desmopressin effect	Avoid
Tricyclic antidepressants	Minor	PD — Additive	↑Hyponatremia risk	Monitor

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Repair Peptides

BPC-157

Drug	Severity	Mechanism	Effect	Recommendation
NSAIDs	Minor	PD — Synergistic	Enhanced GI healing	Safe combination
Antihypertensives	Minor	PD — Additive	↓BP	Monitor
PPIs	Minor	PD — Additive	GI protection additive	Safe combination
Anticoagulants	Minor	PK — Metabolism	Minor interaction	Monitor
Antibiotics	Minor	PK — No interaction	No interaction	Safe combination

Thymosin Beta-4 / TB-500

Drug	Severity	Mechanism	Effect	Recommendation
Corticosteroids	Minor	PD — Synergistic	Enhanced tissue repair	Safe combination
NSAIDs	Minor	PD — Additive	Anti-inflammatory additive	Safe combination
Anticoagulants	Minor	PK — Metabolism	Minor interaction	Monitor
Chemotherapy	Minor	PD — Modulatory	Enhanced repair	Monitor

GHK-Cu

Drug	Severity	Mechanism	Effect	Recommendation
Tetracyclines	Minor	PK — Chelation	↓Both agents	Separate dosing by 2h
Fluoroquinolones	Minor	PK — Chelation	↓Both agents	Separate dosing by 2h
Penicillamine	Minor	PK — Chelation	↓Both agents	Separate dosing
Zinc supplements	Minor	PK — Competition	↓Absorption	Separate dosing

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Somatostatin Analogues

Octreotide

Drug	Severity	Mechanism	Effect	Recommendation
Insulin	Moderate	PD — Synergistic	↑Hypoglycemia	↓Insulin dose
Oral hypoglycemics	Moderate	PD — Synergistic	↑Hypoglycemia	↓Oral hypoglycemic
Cyclosporine	Minor	PK — Absorption	↓Cyclosporine levels	Monitor levels
Bromocriptine	Minor	PK — Absorption	↑Bromocriptine levels	Monitor
Warfarin	Minor	PK — Metabolism	INR fluctuation	Monitor INR
Digoxin	Minor	PK — Absorption	↓Digoxin absorption	Monitor levels
Quinidine	Minor	PK — Absorption	↓Quinidine absorption	Monitor
Beta-blockers	Minor	PD — Additive	Bradycardia risk	Monitor

Lanreotide

Drug	Severity	Mechanism	Effect	Recommendation
Insulin	Moderate	PD — Synergistic	↑Hypoglycemia	↓Insulin dose
Oral hypoglycemics	Moderate	PD — Synergistic	↑Hypoglycemia	↓Oral hypoglycemic
Cyclosporine	Minor	PK — Absorption	↓Cyclosporine levels	Monitor

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Melanocortin Analogues

Melanotan II

Drug	Severity	Mechanism	Effect	Recommendation
Nitrates	Minor	PD — Additive	↓BP additive	Monitor
Antihypertensives	Minor	PD — Additive	↓BP additive	Monitor
MC4R agonists	Minor	PD — Synergistic	Additive effects	Avoid
MAO inhibitors	Minor	PK — Metabolism	↑Melanotan levels	Monitor

Bremelanotide

Drug	Severity	Mechanism	Effect	Recommendation
Naltrexone	Minor	PD — Antagonistic	↓Bremelanotide effect	Monitor
Naloxone	Minor	PD — Antagonistic	↓Bremelanotide effect	Avoid
Other melanocortin agonists	Minor	PD — Synergistic	Additive effects	Avoid

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Thymic Peptides

Thymosin Alpha-1

Drug	Severity	Mechanism	Effect	Recommendation
Immunosuppressants	Moderate	PD — Antagonistic	Opposing effects	Avoid combination
Interferon-alpha	Minor	PD — Synergistic	Enhanced immunity	Monitor
Chemotherapy	Minor	PD — Modulatory	Enhanced immunity	Monitor
Corticosteroids	Minor	PD — Antagonistic	↓Immune response	Monitor

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Antiplatelet Peptides

Eptifibatide

Drug	Severity	Mechanism	Effect	Recommendation
Aspirin	Moderate	PD — Synergistic	↑Bleeding risk	Monitor closely
Heparin	Major	PD — Synergistic	↑↑Bleeding risk	Careful dosing
Clopidogrel	Major	PD — Synergistic	↑↑Bleeding risk	Triple therapy caution
NSAIDs	Moderate	PD — Synergistic	↑Bleeding risk	Avoid if possible
Thrombolytics	Major	PD — Synergistic	↑↑Bleeding risk	Avoid combination

Tirofiban

Drug	Severity	Mechanism	Effect	Recommendation
Aspirin	Moderate	PD — Synergistic	↑Bleeding risk	Monitor closely
Heparin	Major	PD — Synergistic	↑↑Bleeding risk	Careful dosing
NSAIDs	Moderate	PD — Synergistic	↑Bleeding risk	Avoid if possible
Warfarin	Major	PD — Synergistic	↑↑Bleeding risk	Avoid combination

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Insulin Analogues

All Insulin Analogues

Drug	Severity	Mechanism	Effect	Recommendation
Oral hypoglycemics	Moderate	PD — Synergistic	↑Hypoglycemia	↓Dose
Beta-blockers	Moderate	PD — Masking	Mask hypoglycemia symptoms	Educate patient
ACE inhibitors	Minor	PD — Synergistic	↑Hypoglycemia	Monitor
Fluoroquinolones	Minor	PD — Dysglycemia	Glucose fluctuation	Monitor
Corticosteroids	Moderate	PD — Antagonistic	↑Blood glucose	↑Insulin dose
Thiazolidinediones	Moderate	PD — Synergistic	↑Hypoglycemia, ↑edema	↓Insulin dose
MAO inhibitors	Minor	PD — Synergistic	↑Hypoglycemia	Monitor
Salicylates	Minor	PD — Synergistic	↑Hypoglycemia	Monitor
Pentamidine	Minor	PD — Additive	↑Hypoglycemia, then ↑hyperglycemia	Monitor
Lithium	Minor	PD — Additive	↑Lithium levels	Monitor

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General Principles

1. Always monitor glucose when combining any peptide with insulin or oral hypoglycemics
2. Avoid ergot alkaloids with oxytocin (hypertensive crisis)
3. Separate dosing for chelating agents (tetracyclines, fluoroquinolones) with GHK-Cu
4. Monitor INR when combining GLP-1 RAs with warfarin
5. Monitor electrolytes with desmopressin + lithium (water intoxication risk)
6. Avoid triple antiplatelet therapy unless specifically indicated
7. Adjust insulin doses by 20–25% when adding GLP-1 RAs or GH secretagogues
8. Monitor IGF-1 when combining GH secretagogues
9. Separate oral medications by 1–4 hours from GLP-1 RAs (absorption delay)
10. Consult pharmacist for any uncertain interaction

References

• Peptide Interactions Database
• Peptide Clinical Dosing
• Peptide Safety Data
• Peptide Storage Conditions
• Peptide Reconstitution Guide