What Is Symlin?

1. How does Symlin work?

Amylin is co-secreted with insulin by the pancreatic beta cells, so people with type 1 diabetes, who have lost those cells, lack both hormones. It slows gastric emptying, suppresses the glucagon surge after a meal, and signals fullness through receptors in the brainstem. Pramlintide is amylin with three amino acids swapped so it does not clump into fibrils, and it reproduces those effects when injected before a meal, flattening the post-meal glucose curve and, over time, producing modest weight loss.

That mechanism is also behind the weekly amylin drugs now in development, cagrilintide, eloralintide, and petrelintide, pramlintide’s idea with a week-long half-life. Symlin is not a GLP-1 receptor agonist; the two hormone systems overlap in effect but act on different receptors, and only Symlin is approved for type 1 diabetes. The what is a GLP-1 page covers the other system.

2. What is the Symlin dose?

Two ladders, one per diabetes type, both injected immediately before each major meal of at least 250 calories or 30 grams of carbohydrate.

The insulin reduction is the safety-critical step. Pramlintide slows glucose absorption so much that a full mealtime insulin dose injected alongside it can overshoot into hypoglycemia; the label halves the insulin at the start and has the prescriber re-titrate it once the Symlin dose is stable. Symlin and insulin are never mixed in one syringe and are injected at separate sites, into the abdomen or thigh, not the arm, where absorption is more variable.

If a dose is missed, the label says to wait until the next scheduled meal rather than doubling up; if nausea persists at a step, the dose is reduced. The SymlinPen 60 delivered 15 to 60 mcg per click; the SymlinPen 120 delivered 60 and 120 mcg. Each pen was single-patient use only.

Storage follows a two-stage rule. An unused pen is refrigerated at 2°C to 8°C (36°F to 46°F), protected from light, and discarded if it was ever frozen. Once a pen is in use, it can stay refrigerated or be kept at room temperature up to 86°F (30°C), but either way it is used within 30 days of first use, whichever comes first relative to the printed expiration date.

3. How much does Symlin lower blood sugar, and by how much weight?

Modestly on both counts, in three placebo-controlled type 1 trials (26 to 52 weeks) and two type 2 trials (26 and 52 weeks), all published in the label’s clinical studies section and confirmed in the original trial papers.

The change-from-baseline rows show how much HbA1c moved in each arm; the placebo-adjusted row, from the label’s Section 14, is Symlin’s effect isolated from the placebo response, and runs about 0.25 to 0.34 points across trials. Insulin doses were held as stable as possible in these trials to isolate Symlin’s own effect. The independently published versions, by Whitehouse (2002) for type 1 and Hollander (2003) and Ratner (2004) for type 2 and type 1 respectively, report the same direction of effect.

For scale, the weekly GLP-1 agonists lower HbA1c by 1 to 2 points in type 2 diabetes, and weight loss on the newer amylin candidates runs in the double digits as a percentage of body weight (section 7). Symlin’s place was never the size of its glucose or weight effect; it was the type 1 population, where no GLP-1 drug is approved, and the meal-by-meal control it offered people already on intensive insulin.

4. What does the label say about absorption and clearance?

Pramlintide is absorbed and cleared quickly: about 30% to 40% bioavailability, a time to peak concentration around 21 minutes, and an elimination half-life of roughly 48 minutes at the 120 mcg dose, which is why it is dosed with every meal rather than once a day. The arm produced 20% to 36% higher, more variable exposure than the abdomen or thigh, which is why the label directs injections there instead. Renal impairment showed no significant exposure difference in the label’s small comparison, though no dedicated study exists in end-stage renal disease.

5. What are the side effects, contraindications, and interactions?

The boxed warning: Symlin with insulin increases the risk of severe hypoglycemia, particularly in type 1 diabetes, occurring within 3 hours of the injection. The label reserves the drug for people who can recognise hypoglycemia, monitor glucose, and are not already prone to severe lows.

Three contraindications, verbatim: a serious hypersensitivity reaction to Symlin or its components; hypoglycemia unawareness; and confirmed gastroparesis, excluded because Symlin already slows gastric emptying and stacking that effect compounds the risk.

Nausea is the reason both ladders wait for at least 3 nausea-free days before each increase, and why the type 1 ladder climbs in 15 mcg steps; it typically fades over the first weeks. Compared with the GLP-1 class, Symlin has no thyroid C-cell or pancreatitis warning; its risks are the hypoglycemia interaction and the nausea.

Because Symlin slows gastric emptying, the label directs that any oral medicine whose rapid onset matters, its own examples are analgesics, antibiotics, and oral contraceptives, be taken at least 1 hour before or 2 hours after the injection, and that it not be combined with other drugs that slow gastrointestinal motility. Pregnancy and pediatric data are too limited to establish safety, and the label does not recommend pediatric use. Geriatric data, ages 15 to 84, showed no consistent difference in safety or efficacy, though greater sensitivity in some older individuals cannot be ruled out.

6. Was Symlin discontinued?

The openFDA drug shortage database lists two records for pramlintide acetate injection, SymlinPen 60 and SymlinPen 120, both status “To Be Discontinued” as of October 27, 2025.

A “To Be Discontinued” listing is a specific regulatory category, not a statement that the drug is already gone. Under section 506C of the FD&C Act, a manufacturer must notify FDA at least six months before permanently discontinuing a drug that is life-supporting, life-sustaining, or used for a debilitating disease; FDA’s own FAQ calls these entries manufacturer-supplied and informational only. The listing documents a manufacturer’s planned discontinuation; it says nothing about what is on pharmacy shelves today, and the label still posted on DailyMed records labeling, not availability. Current supply is a question for a pharmacy. Anyone using Symlin should confirm supply and, if it cannot be filled, work with a prescriber on the insulin dose, since stopping Symlin removes the reason for the 50% reduction.

7. How does Symlin compare with the newer amylin candidates?

The amylin analogues now in Phase 2 and 3, cagrilintide, eloralintide, and petrelintide, are dosed weekly rather than before each meal and are being tested for weight loss in people without diabetes rather than for mealtime glucose control.

Novo Nordisk’s CagriSema pairs cagrilintide with semaglutide to add amylin’s satiety to GLP-1’s glucose and weight effects, a combination Symlin’s mealtime dosing schedule never made practical. The cagrilintide page picks up that story. For a log, a Symlin entry is product, date, micrograms, the meal, and the injection site, next to the insulin dose taken with it. How GLP-1 tracking works covers what to record.

8. Symlin FAQ

• Is Symlin a GLP-1?

  No. Symlin is pramlintide, an analogue of amylin, a different hormone. Amylin and GLP-1 overlap in effect, both slow the stomach, suppress glucagon, and reduce appetite, but they act on different receptors. Symlin is also the only one of the two classes approved for type 1 diabetes.

• Does Symlin cause weight loss?

  A little, not a weight-loss dose. Across its trials, Symlin produced 0.8 to 1.6 kg of weight loss in type 1 diabetes and 1.4 to 1.6 kg in type 2, versus weight gain on placebo in both. That is far below the weekly GLP-1 drugs, and Symlin is not approved or marketed for weight loss; the same amylin mechanism aimed specifically at weight now drives newer candidates like cagrilintide, eloralintide, and petrelintide.

• What is the Symlin dose?

  Type 1 diabetes: start at 15 mcg immediately before each major meal and increase in 15 mcg steps to a maintenance dose of 30 or 60 mcg, moving up only after at least 3 days without significant nausea. Type 2 diabetes: start at 60 mcg before major meals and increase to 120 mcg, also moving up only after at least 3 days without significant nausea. In both, mealtime insulin is reduced by 50% when Symlin starts, then re-titrated.

• Why does Symlin have a boxed warning?

  Because adding it to insulin increases the risk of severe hypoglycemia, particularly in type 1 diabetes, and when it occurs it is within 3 hours of the injection. Pramlintide itself does not cause hypoglycemia; it slows glucose absorption so much that the insulin already injected can overshoot, which is why the label halves the mealtime insulin at the start.

• Was Symlin discontinued?

  The openFDA drug shortage database lists both SymlinPen 60 and 120 with status "To Be Discontinued," posted October 27, 2025. The label is still posted on DailyMed, which records labeling, not availability. Whether a pharmacy can still fill it is a separate question for the pharmacy and prescriber.

• What does a "To Be Discontinued" listing actually mean?

  Under section 506C of the FD&C Act, manufacturers must notify FDA at least six months before permanently discontinuing a drug that is life-supporting, life-sustaining, or used for a debilitating disease. FDA's own FAQ says these discontinuation entries reflect manufacturer-supplied information and are informational only, not an FDA order pulling the drug from pharmacy shelves.

• Who should not use Symlin?

  The label's contraindications, verbatim: a serious hypersensitivity reaction to Symlin or its components, hypoglycemia unawareness, and confirmed gastroparesis. Oral medicines needing a rapid onset, the label names analgesics, antibiotics, and oral contraceptives, should be taken 1 hour before or 2 hours after the injection.

• What are the side effects of Symlin?

  Nausea above all: 48% versus 17% on placebo in the type 1 trials and 28% versus 12% in type 2. Also vomiting (11% versus 7% in type 1), reduced appetite (17% versus 2%), and headache (13% versus 7% in type 2). Nausea is why both the type 1 and type 2 ladders start low and climb only after at least 3 nausea-free days at each step.

9. Sources