What is the difference between gabapentin and gralise

Because of this, they can both undergo facilitated transport across cellular membranes through system L-amino acid transporters. However, pregabalin may either have an additional system of absorption or be better transported than gabapentin, as it is almost completely absorbed, while gabapentin is not. In addition, absorption of gabapentin is limited to the small intestine, while pregabalin is absorbed throughout the small intestine and extending to the ascending colon.

Gabapentin is more slowly and variably absorbed, with peak plasma concentrations around 3 hours post-dose. Pregabalin is quickly absorbed, with the maximum rate of absorption being 3 times that of gabapentin. It reaches peak blood concentrations within an hour after ingestion.

Absorption of gabapentin is saturable, leading to a non-linear pharmacokinetic profile. As gabapentin doses increase, the area under the curve AUC does not follow proportionally.

Unlike gabapentin, absorption of pregabalin is not saturable, and the drug has a linear pharmacokinetic profile. In contrast, the AUC of pregabalin is unaffected by food, though absorption is slower. Distribution of gabapentin and pregabalin is very similar.

Neither agent is bound by great extent to any plasma proteins, decreasing the likelihood of drug interactions due to protein binding. Both have high aqueous solubility, and the volume of distribution of each is similar 0. Drug-drug interactions are unlikely for both pregabalin and gabapentin. Neither pregabalin nor gabapentin is affected by cytochrome CYP drug interactions, as neither drug is metabolized by CYP enzymes.

Agents that decrease small bowel motility can theoretically cause an increase in the absorption of gabapentin, because it is not completely absorbed. Gabapentin is also available in 2 extended-release formulations: a tablet Gralise and a gastro-retentive prodrug, gabapentin enacarbil Horizant.

Both have different pharmacokinetics and are not interchangeable with standard formulations, the original of which is Neurontin. Side effects of these newer formulations are similar to standard formulations. Gralise is indicated for postherpetic neuralgia and taken as an mg maintenance dose once a day.

The AUC of mg of Gralise is slightly less than mg of the standard formulation. In addition, the average maximum concentration Cmax of Gralise is slightly higher than mg of the standard form, and minimum concentration Cmin is slightly lower. Finally, Tmax is increased in the extended-release form. Horizant is a prodrug of gabapentin indicated for postherpetic neuralgia and restless leg syndrome. The recommended maintenance dose is mg twice a day. Doses greater than mg daily are not recommended, as side effects increase without a corresponding increase in efficacy.

It is absorbed through the small intestine through a proton-linked monocarboxylate transporter MCT Unlike the original formulation, absorption of gabapentin enacarbil is not saturated at high doses, as MCT-1 is expressed in high levels in the intestinal tract.

The drug undergoes near-complete first pass hydrolysis to gabapentin by non-specific carboxylesterases mainly in enterocytes, as well as in the liver to a lessor degree. Consumption of alcohol increases the release of gabapentin enacarbil from the extended-release tablet.

Therefore, alcohol should be avoided when taking Horizant due to increased risk of side effects. Like standard formulations of gabapentin, Gralise and Horizant are not metabolized to an appreciable extent by phase I metabolism, and they are neither a substrate nor an inhibitor of p-glycoprotein.

All forms of gabapentin must be adjusted in renal dysfunction, similar to standard formulations. One review found that these extended-release formulations have similar efficacy to standard ones, and they might also have fewer adverse events. Both pregabalin and gabapentin are well tolerated.

With both drugs, side effects are dose dependent and reversible if the medication is discontinued. When discontinuing gabapentin it is recommended to taper the dose over a week at least. Gabapentin and pregabalin vary in terms of binding affinity and potency. Pregabalin has an increased binding affinity for the alphadelta protein and is a more potent analgesic in neuropathic pain compared with gabapentin.

One study developed a population pharmacokinetic model comparing pregabalin with gabapentin. Based on studies of gabapentin and pregabalin in epilepsy, the EC50 values of pregabalin and gabapentin were estimated to be about 9.

Using studies in postherpetic neuralgia, the EC50 values of pregabalin and gabapentin were estimated to be about 4. Based on these values, pregabalin was estimated to be about 2. One study analyzed data from phase 2 trials of gabapentin and pregabalin and created a pharmacodynamic model.

Pregabalin also exhibited a steeper dose-response curve than gabapentin. For clinicians who wish to convert patients from gabapentin to pregabalin, there are a few studies that reviewed such a conversion. One cohort study reviewed the utility of switching patients with neuropathic pain due to peripheral neuropathy from gabapentin to pregabalin. The authors also stratified the pregabalin group further into those who responded well or poorly to gabapentin, with gabapentin stopped after the nighttime dose and pregabalin started the following morning.

The authors found that those who responded well to gabapentin and those who did not showed additional benefit with decreased pain when they were switched to pregabalin.

Patients taking pregabalin also had improved pain control compared with those who remained on gabapentin. Program eligibility and restrictions apply. Normally, nerves send signals to tell the brain when your body is being harmed. These signals protect you. The shingles virus can damage nerves and cause them to send the wrong signals to your brain.

The result is postherpetic neuralgia PHN. Pain after shingles can affect your emotional well-being, your sleep, your ability to carry out your daily activities, and your desire to participate in social activities. There are an estimated 1 million cases of shingles in the US each year. Like other antiepileptic drugs, gabapentin, the active ingredient in GRALISE, may cause suicidal thoughts or actions in a very small number of people, about 1 in Call a healthcare provider right away if you have any of these symptoms, especially if they are new, worse, or worry you:.

Tell your healthcare provider about all the medicines you take including prescription and non-prescription medicines, vitamins or herbal supplements. Especially tell your healthcare provider if you take any opioid pain medicine such as oxycodone , or medicines for anxiety such as lorazepam or insomnia such as zolpidem.

Do not start or stop other medicines without talking to your healthcare provider. Do not drink alcohol or take other medicines that make you sleepy or dizzy while taking GRALISE without first talking to your healthcare provider. Tell your healthcare provider about any side effect that bothers you or that does not go away.

For more information, ask your healthcare provider or pharmacist. Call your doctor for medical advice about side effects. You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www. Please see the full Prescribing Information , including Medication Guide. References: 1. Clin J Pain. Relationship between pain relief, reduction in pain-associated sleep interference, and overall impression of improvement in patients with postherpetic neuralgia treated with extended-release gabapentin.

Health and Qual Life Outcomes. Clinical development of a once-daily gastroretentive formulation of gabapentin for treatment of postherpetic neuralgia: an overview.