CJC-1295 and Simvastatin Interaction: What Patients and Prescribers Need to Know

Is there a known interaction between CJC-1295 and simvastatin?

No interaction between the two has been measured in the human CJC-1295 studies FDA identified, so there is no measured answer on whether one changes the other.

CJC-1295 is not an FDA-approved drug [2]. FDA identified only three published human studies of it (Teichman 2006, Ionescu and Frohman 2006 and Sackmann-Sala 2009), all of the DAC form, all in healthy volunteers, and none in people with a disease [2]. Their reported outcomes were hormone levels, the peptide's own pharmacokinetics and short-term adverse events, not a CJC-1295/simvastatin interaction [2][9][10]. Simvastatin is metabolized by CYP3A4, and the Zocor label contraindicates strong CYP3A4 inhibitors and sets dose limits with several other interacting drugs [4].

Two questions sit inside the pairing: whether CJC-1295 changes simvastatin blood levels, and whether the two drugs add to each other's harm. Simvastatin's side has real numbers behind it. CJC-1295's side is measured in hormone levels, not drug levels.

What simvastatin's own interactions look like

Simvastatin is a prodrug, hydrolysed after dosing to simvastatin acid, which inhibits HMG-CoA reductase, the rate-limiting enzyme that converts HMG-CoA to mevalonate. It is metabolized by CYP3A4, and simvastatin acid is a substrate of the transporter OATP1B1; under 5% of an oral dose reaches the general circulation because the liver extracts so much on first pass [4].

The Zocor label contraindicates strong CYP3A4 inhibitors, cyclosporine, danazol and gemfibrozil. In the label's studies, itraconazole 200 mg daily raised the AUC of simvastatin acid and of simvastatin about 13-fold each, telithromycin raised them 12-fold and 8.9-fold, and nelfinavir 6-fold and 6.2-fold [4]. The label says that if short-term treatment with a strong CYP3A4 inhibitor is unavoidable, Zocor should be suspended for its duration [4].

Other drugs get dose caps rather than bans. The label says not to exceed 20 mg daily with amlodipine, amiodarone or ranolazine, and not to exceed 10 mg daily with verapamil, diltiazem or dronedarone [4]. The label's maximum recommended dose is 40 mg once daily, and 80 mg is limited to people who have taken it chronically, for example 12 months or more, without muscle toxicity. The 5 mg and 80 mg Zocor tablets are no longer marketed [4].

The Zocor label says to avoid grapefruit juice because it can raise simvastatin levels and the risk of myopathy and rhabdomyolysis [4]. In a randomized crossover study of 10 healthy volunteers, 200 mL of double-strength juice three times daily for two days plus a 60 mg simvastatin dose raised simvastatin AUC 16-fold and simvastatin acid AUC about 7-fold [7].

How often simvastatin causes muscle problems

The Zocor label reports myopathy (unexplained muscle weakness, pain or tenderness with CK above 10 times the upper limit of normal) in about 0.03% on 20 mg, 0.08% on 40 mg and 0.61% on 80 mg among 24,747 treated patients, with risk highest in the first year. It also reports acute kidney injury from myoglobinuria and rare fatalities with statins [4]. SEARCH, a double-blind trial in 12,064 survivors of myocardial infarction, compared 80 mg with 20 mg daily for a mean of 6.7 years and found myopathy in 53 people on 80 mg (0.9%) versus 2 on 20 mg (0.03%) [1]. The label quotes rhabdomyolysis for that trial as about 0.4% on 80 mg versus about 0% on 20 mg [4].

The label lists age 65 or older, uncontrolled hypothyroidism, renal impairment, interacting drugs and higher dose as risk factors. It reports myopathy in about 0.24% of Chinese patients versus 0.05% of non-Chinese patients in a 40 mg trial [4]. Genetics matter as well: in a genomewide study of 85 people with definite or incipient myopathy on simvastatin 80 mg and 90 controls, the SLCO1B1 rs4149056 C allele raised the odds of myopathy 4.5-fold per copy (95% CI 2.6 to 7.7) and 16.9-fold in CC compared with TT, and more than 60% of cases were attributable to the variant [8].

What the CJC-1295 studies actually measured

Teichman 2006 ran two randomized, placebo-controlled, double-blind, ascending-dose trials of 28 and 49 days in healthy adults aged 21 to 61, with single doses in the first and two or three weekly or biweekly doses in the second. FDA counted 35 treated subjects and 7 on placebo in study 1 [2][9]. After one injection the estimated half-life was 5.8 to 8.1 days, mean GH rose 2- to 10-fold for six days or more and IGF-I 1.5- to 3-fold for 9 to 11 days, and after multiple doses IGF-I stayed above baseline for up to 28 days. No serious adverse reactions were reported [9]. The events FDA summarizes are injection-site reactions in about 70% of study 1 and in all treated subjects in study 2, headache in 63% versus 14% on placebo, flushing, warmth and transient low blood pressure in about 30%, transient diarrhea, and transient dizziness and low blood pressure in two subjects. Most were more common at 125 or 250 micrograms/kg [2].

Ionescu and Frohman 2006 gave healthy men aged 20 to 40 a single 60 or 90 micrograms/kg dose. A week later trough GH was 7.5-fold higher, mean GH 46% higher and IGF-I 45% higher, and GH pulses were preserved. The reported events were a dose-dependent rise in heart rate and transient injection-site redness and tenderness [10][2].

FDA's briefing says ConjuChem withdrew CJC-1295 DAC from clinical trials in 2006 after a participant in a phase 2 trial in HIV lipodystrophy (192 enrolled) died. FDA cites anecdotal news reports that the attending physician's most likely explanation was undiagnosed coronary artery disease with plaque rupture. The data were never published, so a causal link to the drug is neither shown nor excluded [2].

What the human data do and do not show

The three human studies reported hormone levels, the peptide's own pharmacokinetics and adverse events as their outcomes [9][10][2]. They show that the DAC peptide lifts the hormone axis substantially: one 60 or 90 micrograms/kg injection raised trough GH about 7.5-fold a week later, with mean GH up 46% and IGF-I up 45% [10]. They did not measure effects on CYP3A4 or on simvastatin levels.

FDA's position on growth hormone-raising peptides is that GH and IGF-I elevation carries the risks listed on approved growth hormone labels, including glucose intolerance and diabetes, fluid retention and tumor growth concerns. FDA also said the CJC-1295 studies were short, small and mostly single-dose, leaving long-term safety unknown [2]. Separately, the Zocor label reports increases in HbA1c and fasting glucose [4].

What CJC-1295's regulatory status means here

FDA found no approved product containing any form of CJC-1295 in the twelve countries it searched, and none authorized by the European Medicines Agency [2]. On December 4, 2024, FDA's Pharmacy Compounding Advisory Committee voted 0 yes and 13 no on the free base, 1 yes and 12 no on the acetate, and 0 yes and 13 no on each of the three DAC forms [11]. CJC-1295 is in none of the three categories on FDA's list for state-licensed pharmacies and is not on FDA's outsourcing-facility list. It has no USP monograph and is not part of an approved drug, so FDA's category 1 policy does not apply to it [5][6]. FDA lists it in the table of substances previously in category 2 and later withdrawn by the nominators, and its posted concerns remain: possible immunogenicity for certain routes, impurity and characterization problems, serious adverse events including increased heart rate and systemic vasodilatory reaction, and limited clinical data [3]. FDA noted that CJC-1295 sold online is mostly labeled research use only, often in blends with ipamorelin and GHRPs, and that research-use-only products are not FDA-approved drugs [2].