Diabetes in Pets
Iletin II Lente
Lente by Eli Lilly
intermediate-acting Porcine
U100 Lente
Line Iletin
Also known as pork lente
Similar to  
Action in cats  
  • onset X-Xh,
  • sharp peak X-Xh,
  • duration X-Xh
Action in dogs  
  • onset <1h,
  • gentle peak 4-8h,
  • duration 14-24h
Use and Handling
Type cloudy
Shelf Life 24 months
When opened 28 days room temp.
In pen N/A

A 100% porcine U100 insulin formerly produced by Eli Lilly[1], discontinued in 2003[2] and comprised of 30% semilente insulin and 70% Ultralente insulin[3].

Like all other Lente insulins[4] it was a suspension of crystalline (ultralente) and amorphous (semilente) insulins in the ratio shown above[5][6].

It is identical to Monotard Pork, which Novo Nordisk also used to produce. It is also identical to Caninsulin[7][8] and Vetsulin in all respects except strength; they are U40 insulins.

What Lente Is Not

No Lente-type insulin regardless of species can contain any NPH/isophane insulin[9] or any R/Neutral insulin[10].

Both are chemically impossible: the phenol preservative present in NPH/isophane alters the action of Lente-type insulins, creating a mixture with an approximate action of R/Neutral[11].

The zinc suspension of Lente-type insulin binds R/Neutral, causing the short-acting insulin to slow, losing its short-acting effect[12][13][14].

Combining Lente Family Insulins

Insulin manufacturers[15] indicate that R/neutral and semilente, Lente, ultralente insulins are able to be combined in the same syringe, but only just before injection. In pre-filled syringes, the zinc suspension of the Lente-type insulins binds the R/neutral, causing it to lose its short-acting effect. Various studies have documented this, and some doctors advise against using R/neutral in the same syringe with the Lente family of insulins[16][17][18][19].

None of the Lente family of insulins (semilente, Lente, Ultralente) can be combined with[20] NPH/isophane insulins. The phenol preservatives present in NPH-type insulins alters the Lente-types to the point where they become a close approximation of R/neutral, with regard to action[21].

Keeping the phenol preservatives in mind, all protamine-suspended insulin mixes would be "off limits" regarding same syringe mixing with any Lente-type insulins[22].


  1. Drugs.com-Copy of Iletin II Lente Patient Information Leaflet
  2. US-FDA Iletin II Lente Discontinuation Material 2003
  3. Iletin II Lente-Lente Pork Insulin
  4. EMEA Scientific Discussion-Monotard
  5. Iletin II Lente Carton Illustration
  6. Iletin II Lente carton photo
  7. Horn Mitten Study-Refers to the Church Study Equating Caninsulin with Novo's old Pork Monotard
  8. Australian Veterinary Journal-More Re: Caninsulin Being Equivalent to Pork Monotard
  9. Combining Lente-type Insulins with Phenol-Preserved Insulins
  10. Lente Zinc Suspension Causes Loss Of R/Neutral Short-Acting Effect
  11. Lente-Type Insulins & NPH/Isophane Insulins-A Bad Combination
  12. Intermediate-Acting Insulin Preparations: NPH (Isophane) & Lente Diabetes Care-1980
    Note--in 1980, there was only beef Lente-type insulin--no pork or r-DNA/GE/GMLente insulins
  13. Solubility Changes on Mixing Short- and Long-acting Insulin Preparations-South African Medical Journal-1988
  14. Resource Guide 2005-American Diabetes Association
  15. Insulin Producers vs Doctors Re:Combining R/Neutral & Lente-type Insulins
  16. Availability of Soluble (R/Neutral) Insulin in Mixed Preparations of Crystalline (Lente) & Ultralente GE Insulins-Clinical Therapeutics-1991
  17. Absorption Kinetics & Action Profiles-Single Subcutaneous Administration of Human Soluble (R/Neutral) & Lente Insulin-Diabetes Care-1987
  18. Delayed Onset of Action of Soluble (R/Neutral) Insulin After Premixing With Lente Insulin Diabetes Research & Clinical Practice-1983
  19. RxEd.org-Insulin Therapy-Mixing Precautions
  20. Phenol Preservatives & Lente-type Insulins--A Bad Combination
  21. RxEd.org-Insulin Therapy-Mixing Precautions
  22. RxEd.org-Insulin Therapy-Mixing Precautions