Gabapentin and Pregabalin are “nerve ending medications” used in treatment for Sensory Neuropathic Cough (SNC) and Sensory Neuropathic Throat Clearing (SNTC).
Background
Sensory Neuropathic Cough (SNC) is conceptualized as a “cousin” to neuralgia. It is a primary neuropathic problem, presumed to be the result of “nerve ending damage.” Neuralgia is primary neuropathic pain. By contrast, SNC is the result of primary neuropathic dysesthesia: an abrupt tickle, dry patch, itching, dust sensation, dripping, etc. the aberrant sensation that triggers coughing (or throat clearing or laryngospasm) is not pain, but instead a tickle, pinprick, sudden dry patch, dripping sensation, feeling of sudden “dust” in the throat. Etc.
Causation
Sometimes the cause seems clear: “I was dreadfully ill with bronchitis, coughed my head off, and after a lot of medication became well again, but the cough never went away.” Or, “This started a few months after my thyroid surgery.” But at least 50% of patients cannot identify any apparent cause. “I just started coughing”, they say. In any case, it seems that damaged nerve endings somewhere in the throat have become jittery, and fire too easily.
Treatment
And so, the treatment is what we call ”nerve ending stabilizing medicines.” This is usually a medication by mouth, but could be an injection, capsaicin spray, etc. Gabapentin (or, rarely, pregabalin) represent a major choice of medication to raise the threshold of firing of these “jittery, unstable” nerve endings. More information on SNC is found here and here and here.
Gabapentin and Pregabalin
These “nerve ending medications” also go by the trade names of Neurontin and Lyrica, respectively. We use gabapentin far more than pregabalin.
Details of Administration
We begin with 300 mg before bed for 3 days. Then 300 mg at noon and bedtime (600 mg total) for 3 days. Then 300 mg breakfast, mid-afternoon, and bedtime (900 mg total) for 3 days. And finally, 300 mg breakfast, lunch, dinner, and bedtime (1200 mg total). We suggest that the first three doses of the day be taken with food to reduce potential side effects; no food is needed at bedtime. See example.
Why 4 times a day, rather than the more usual schedule of three times a day? Because shortening the duration between doses seems to confer better results than the longer interval. That is, 600 mg three times a day (total of 1800 mg per day) may not work as well as 300 mg four times a day (total of 1200 mg per day). Furthermore, to take the medication at breakfast, lunch, dinner, and bedtime is easier to remember than breakfast, mid-afternoon, and bedtime. The mid-afternoon dose is hard to remember.
Expected Relief
Few patients experience total relief, but benefit is usually major. Most can reach at least “70 or 80% reduction of symptoms.” If that level of relief is reached, 1200 mg would be the ongoing dose level. If less than that, then up-titration can continue using the same sequence above until reaching 2400 mg per day, and even 3600 mg per day. We consider that there is no absolute limit based in milligrams; instead it is primarily side effects that determine maximum dose per day. Commonest dose levels are between 1200 and 2400 mg per day.
Side Effects
Some have virtually none, even at high doses, especially if they take the first three doses of the day with food. Others have noticeable effects, even at modest doses. Such persons may up-titrate using 100 mg capsules rather than the more common 300 mg denomination. And the build-up can be stretched to once a week, rather than every three days. If up-titration is very gradual, those sensitive to side effects are often able to reach at least 800, if not 1200 mg per day.
What are the primary side effects? First, would be the realm of sleepiness, a “foggy head,” or things like reduced function of short term memory. These side effects do not imply damage to the brain. That is, if the medication is discontinued, these side effects go away. The other main side effect is ataxia. This is not dizziness (feeling of spinning) or light-headedness (like one might faint), but instead a “drunken sailor” sensation of being “off kilter.”
Duration of Treatment
Patients stay on Neurontin indefinitely if symptoms are under very good control (80% reduction or more) for a fairly stable and extended period of time. If symptoms really diminish even more, you can try to taper gradually off of the medication. We say “tiptoe out of the room to see if the monster stirs or awakens.” You drop one pill per week and see if the cough increases. If you notice it does (even if you only reduced by one pill a day) you go back up to full dosage. If no increase of coughing, drop another pill per week until you are completely off the medication. Note that even those who successfully taper entirely from the medication, the next upper respiratory infection may reawaken the SNC. And note as well that gabapentin / pregabalin will not work well during upper respiratory infections. We say “viral infection makes the monster thrash around about 3 weeks, before the cough settles back to baseline.” During the 3 weeks, if necessary, we occasionally use tramadol or a similar medication to suppress the cough.