Tesamorelin Drug Interactions: What to Avoid and What to Tell Your Doctor

Tesamorelin (Egrifta SV, Egrifta WR) is a growth hormone-releasing factor analog that works by stimulating the pituitary gland to release growth hormone. Because growth hormone affects multiple metabolic pathways — including how the liver processes certain drugs — tesamorelin can interact with other medications you may be taking. This guide explains the key drug interactions you need to know about before starting tesamorelin.

Always tell your doctor and pharmacist about every medication you take — including prescription drugs, over-the-counter medicines, vitamins, and herbal supplements — before starting tesamorelin.

Why Tesamorelin Causes Drug Interactions

The primary reason tesamorelin interacts with other drugs is that growth hormone alters the activity of liver enzymes — specifically the CYP450 enzyme system — that metabolize many common medications. When tesamorelin increases GH levels, it changes how quickly these enzymes break down other drugs in your body. This can cause drug levels to be higher or lower than expected.

Interaction 1: Glucocorticoids (Cortisone, Prednisone) — Serious, Avoid or Monitor Closely

Tesamorelin has a significant interaction with glucocorticoid medications such as cortisone and prednisone. Growth hormone stimulates the enzyme 11β-hydroxysteroid dehydrogenase (11β-HSD), which converts cortisone to its active form, cortisol, in the liver and fat tissue. When tesamorelin is added, this conversion process is enhanced, which can reduce the effective levels of cortisone and prednisone in patients who take them as replacement therapy for adrenal insufficiency (hypoadrenalism).

For patients on glucocorticoid replacement therapy, the FDA recommends: monitor for reduced glucocorticoid effects after starting tesamorelin, and consider increasing the maintenance or stress dose if needed. Cortisone in particular requires special attention because it depends most heavily on this conversion process.

Interaction 2: Estrogens and Hormonal Contraceptives — Moderate, Monitor or Change Method

Tesamorelin reduces the levels of estrogen-based medications by accelerating their metabolism through CYP3A4 enzymes in the liver. This includes:

Oral estrogen contraceptives (birth control pills containing estrogen)

Hormone replacement therapy containing estradiol

Norethindrone and other progestins metabolized by CYP3A4

Because tesamorelin may reduce the effectiveness of hormonal contraception, patients who use oral contraceptives should discuss using a non-hormonal or alternative contraceptive method with their doctor. This is especially important given that tesamorelin is absolutely contraindicated during pregnancy.

Interaction 3: Anticonvulsants — Monitor Drug Levels

Phenytoin (Dilantin) levels can be reduced when tesamorelin is added, because tesamorelin alters hepatic enzyme activity. If you take phenytoin for epilepsy or another seizure disorder, your doctor should monitor your phenytoin blood levels after starting tesamorelin and may need to adjust your dose. Other anticonvulsants metabolized by CYP enzymes — including carbamazepine and valproate — may also be affected and should be monitored.

Interaction 4: Theophylline — Monitor Levels

Theophylline — a drug used for asthma and COPD — decreases the levels of tesamorelin by altering metabolism. This interaction goes in the opposite direction: theophylline may reduce the effectiveness of tesamorelin. If you are on theophylline and tesamorelin, your doctor may need to monitor both levels.

Interaction 5: Cyclosporine — Monitor Immunosuppression

Cyclosporine (used to prevent organ rejection after transplant or to treat autoimmune conditions) is metabolized by CYP3A4. Tesamorelin can alter cyclosporine metabolism, potentially changing drug levels. If you take cyclosporine, your doctor should monitor your cyclosporine levels and adjust as needed after starting tesamorelin.

Interaction 6: HIV Antiretrovirals — Specifically Ritonavir

Co-administration of tesamorelin with ritonavir (a common HIV medication used as a pharmacokinetic booster) resulted in a 9% decrease in ritonavir AUC and 11% decrease in peak concentration (Cmax). This modest effect is unlikely to compromise ritonavir's effectiveness at standard doses, but it is worth noting for your prescribing HIV specialist to track.

Interaction 7: Macimorelin (Diagnostic Test Drug)

Macimorelin is a medication used as a diagnostic test for adult growth hormone deficiency. If you are scheduled for a macimorelin test, you must stop tesamorelin at least one week before the test. Tesamorelin's GH-stimulating effect will blunt the growth hormone response to macimorelin, making the diagnostic test unreliable.

Important: Blood Sugar Interactions with Diabetes Medications

Tesamorelin can cause glucose intolerance and raise blood sugar levels. This creates an indirect interaction with diabetes medications: if tesamorelin worsens your blood sugar control, your diabetes medications (insulin, metformin, GLP-1 agonists, etc.) may need adjustment. Monitor your blood glucose closely after starting tesamorelin and report any significant changes to your doctor promptly.

For a full review of tesamorelin side effects beyond drug interactions, see our guide on tesamorelin side effects and when to call your doctor. And if you need help finding a specialty pharmacy that has tesamorelin in stock, medfinder can call pharmacies near you on your behalf.