Peptide Physician Guides

This reference provides evidence-based prescribing information for major peptide therapeutics, organized by therapeutic class with dosing protocols, monitoring requirements, and clinical decision support.

GLP-1 Receptor Agonists Prescribing Guide

Indication-Specific Dosing

Type 2 Diabetes

Agent	Starting Dose	Titration	Maximum Dose	Frequency
Semaglutide (Ozempic)	0.25 mg	0.5 mg at 4 weeks → 1 mg	2 mg	Once weekly
Tirzepatide (Mounjaro)	2.5 mg	5 mg at 4 weeks → 10 mg	15 mg	Once weekly
Liraglutide (Victoza)	0.6 mg	1.2 mg at 1 week → 1.8 mg	1.8 mg	Once daily
Dulaglutide (Trulicity)	0.75 mg	1.5 mg at 4 weeks	1.5 mg	Once weekly
Exenatide (Byetta)	5 µg BID	10 µg BID at 1 month	10 µg BID	Twice daily

Obesity

Agent	Starting Dose	Titration	Maximum Dose	Frequency
Semaglutide (Wegovy)	0.25 mg	0.5 mg → 1 mg → 1.7 mg → 2.4 mg	2.4 mg	Once weekly
Tirzepatide (Zepbound)	2.5 mg	5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg	15 mg	Once weekly
Liraglutide (Saxenda)	0.6 mg	1.2 mg → 1.8 mg → 2.4 mg → 3 mg	3 mg	Once daily

Clinical Decision Algorithm

Patient with T2D and obesity (BMI ≥30):

1. First-line: Metformin + lifestyle modification
2. Second-line: Add GLP-1 RA with dual benefit (semaglutide or tirzepatide)
3. Selection criteria:
   • Primary CV risk → semaglutide (CVOT evidence)
   • Maximum weight loss → tirzepatide (greater efficacy)
   • Cost sensitivity → dulaglutide or liraglutide
   • Oral preference → semaglutide (Rybelsus)

Patient with T2D and established CVD:

1. First-line: GLP-1 RA with CV benefit (semaglutide or liraglutide)
2. Selection criteria:
   • CV death reduction → liraglutide (LEADER)
   • MACE reduction → semaglutide (SUSTAIN-6)
   • Oral preference → semaglutide (Rybelsus)

Monitoring Protocol

Parameter	Baseline	3 Months	6 Months	Annually
HbA1c	✓	✓	✓	✓
Fasting glucose	✓	✓	✓	✓
Weight	✓	✓	✓	✓
Blood pressure	✓	✓	✓	✓
Renal function (eGFR)	✓	✓	✓	✓
Lipid panel	✓	—	✓	✓
Hepatic function	✓	—	✓	✓
Thyroid function	✓	—	—	✓
Pancreatic enzymes	If symptoms	If symptoms	If symptoms	If symptoms

Insulin Prescribing Guide

Basal Insulin Selection

Agent	Onset	Peak	Duration	Hypoglycemia Risk	Cost
Glargine U-100	2–4 hr	8–12 hr	24 hr	Moderate	Low
Glargine U-300	6 hr	12–16 hr	36 hr	Low	High
Degludec	30–90 min	~9 hr	>42 hr	Lowest	High
Detemir	1–2 hr	6–12 hr	12–18 hr	Moderate	Moderate

Selection Algorithm:

1. Insulin-naïve: Start glargine U-100 or U-300 at 10 units daily
2. Nocturnal hypoglycemia: Switch to glargine U-300 or degludec
3. Maximum flexibility: Degludec (any time of day)
4. Cost-sensitive: Glargine U-100 biosimilar

Rapid-Acting Insulin Selection

Agent	Onset	Peak	Duration	Ultra-Rapid Option
Lispro (Humalog)	5–15 min	1–3 hr	3–5 hr	Lyumjev
Aspart (NovoRapid)	5–15 min	1–3 hr	3–5 hr	Fiasp
Glulisine (Apidra)	10–15 min	1–1.5 hr	3–5 hr	No

Insulin Initiation Protocol

T2D - Basal Insulin Start:

1. Starting dose: 10 units SC once daily (or 0.1–0.2 units/kg)
2. Timing: Bedtime or morning (patient preference)
3. Titration: Increase by 2 units every 3–4 days to fasting glucose target (80–130 mg/dL)
4. Maximum initial dose: 0.5 units/kg/day
5. Add prandial insulin: If fasting glucose at target but HbA1c above goal

T1D - Basal-Bolus Start:

1. Basal dose: 50% of total daily dose (TDD), split into 1–2 daily injections
2. Bolus dose: 50% of TDD, divided among meals (carb counting)
3. ICR (insulin-to-carb ratio): 500/TDD = grams of carbs covered by 1 unit
4. ISF (insulin sensitivity factor): 1800/TDD = mg/dL drop per 1 unit

GH Secretagogue Prescribing Guide

Tesamorelin (Egrifta)

Parameter	Recommendation
Indication	HIV-associated lipodystrophy with excess abdominal fat
Dose	2 mg SC once daily
Timing	Within 2 hours before or after a meal
Monitoring	IGF-1 every 3 months; fasting glucose
Duration	Reassess at 6 months; continue if benefit maintained
Contraindications	Active malignancy, pregnancy, pituitary disease

Monitoring Protocol (GH Secretagogues)

Parameter	Baseline	1 Month	3 Months	6 Months	Annually
IGF-1	✓	—	✓	✓	✓
Fasting glucose	✓	✓	✓	✓	✓
HbA1c	✓	—	✓	—	✓
Prolactin (GHRP-6 only)	✓	—	✓	—	✓
Cortisol (GHRP-6 only)	✓	—	✓	—	✓
Thyroid function	✓	—	—	—	✓

GnRH Analogue Prescribing Guide

Prostate Cancer

Agent	Dose	Route	Frequency	Duration
Leuprolide (Lupron Depot)	7.5 mg	IM	Monthly	Until progression
Leuprolide (Lupron Depot-3M)	22.5 mg	IM	Every 3 months	Until progression
Leuprolide (Lupron Depot-6M)	45 mg	IM	Every 6 months	Until progression
Goserelin (Zoladex)	3.6 mg	SC implant	Monthly	Until progression
Goserelin (Zoladex-3M)	10.8 mg	SC implant	Every 3 months	Until progression

Monitoring (GnRH Analogues)

Parameter	Frequency	Notes
Testosterone	Every 3–6 months	Target: castrate level (<50 ng/dL)
PSA	Every 3–6 months	Monitor for response
Bone density (DEXA)	Baseline + annually	Androgen deprivation risk
Cardiovascular risk	Baseline + annually	Metabolic effects
Hot flashes	Ongoing	Manage with lifestyle/medications

Drug Interactions

GLP-1 Receptor Agonists

Interacting Drug	Effect	Management
Insulin	Additive hypoglycemia risk	Reduce insulin dose by 20–30%
Sulfonylureas	Additive hypoglycemia risk	Reduce SU dose by 50%
Warfarin	INR may increase	Monitor INR closely
Oral contraceptives	Reduced efficacy (delayed absorption)	Use alternative contraception
Metformin	Complementary efficacy	First-line combination

Insulins

Interacting Drug	Effect	Management
Beta-blockers	Mask hypoglycemia symptoms	Educate on glucose monitoring
Thiazolidinediones	Fluid retention, heart failure risk	Monitor for edema
ACE inhibitors	Increased hypoglycemia risk	Monitor glucose closely
Corticosteroids	Hyperglycemia	Increase insulin dose
Alcohol	Hypoglycemia risk (delayed)	Educate on alcohol and insulin

Contraindications and Precautions

GLP-1 Receptor Agonists

Contraindication	Evidence
Personal/family history of medullary thyroid cancer	Boxed warning
Multiple Endocrine Neoplasia syndrome type 2	Boxed warning
History of pancreatitis	Use with caution
Severe GI disease (gastroparesis)	Use with caution
Pregnancy	Not recommended
Severe renal impairment (eGFR <30)	Limited data

Insulins

Contraindication	Evidence
Hypoglycemia	Relative contraindication
Hypokalemia	Monitor potassium
Severe hepatic impairment	Dose reduction needed

GnRH Analogues

Contraindication	Evidence
Pregnancy	Teratogenic
Known hypersensitivity	Anaphylaxis risk
Vertebral metastases (women)	Spinal cord compression

Summary

Peptide prescribing requires careful consideration of indication, dosing, monitoring, drug interactions, and contraindications. GLP-1 RAs are first-line for T2D with obesity or CVD; insulin is essential for T1D and advanced T2D; GH secretagogues serve specific indications (HIV lipodystrophy); GnRH analogues are cornerstone therapies for hormone-sensitive cancers. Monitoring protocols should be tailored to the specific peptide and patient population, with attention to drug interactions and contraindications.