Gabapentin misuse

By Professor Saman Gunatilake

Consultant Neurologist

As prescribing physicians, we should be happy about the initiative taken by the State Minister of Pharmaceutical Production and the Sri Lanka Pharmaceutical Manufacturing Corporation (SPMC) to produce essential drugs, locally. This would definitely help our patients if the quality is assured and also help the country save millions of rupees currently spent on purchasing them from foreign vendors. The newspapers this week reported that the drug, gabapentin, had been produced by the SPMC. I am intrigued. Why gabapentin was the first choice to be produced locally? It has been mentioned that Rs. 65 million is spent on this drug annually, the implication being that this is an important and widely used drug. As a practising neurologist, well aware of the prescribing habits of doctors, I would agree that it is widely prescribed, but most of the times unnecessarily. Whether this drug is so important as to be made here for wider use is debatable, and the general opinion of the international experts is that it is a drug very extensively misused. In this country, too, large sales of this drug are due to its use for conditions and situations where it is really not indicated. The pharmaceutical industry and its representatives have promoted this drug for use in many conditions where it is not licensed to be used. Our drug market is flooded with generic products of this drug with different brand names, imported from several countries.

The misuse of medicines is defined as use of a substance for a purpose not consistent with legal or medical guidelines, such as taking another person’s medication or taking a higher dosage than prescribed. The Prescription drug misuse is a problem, especially psychoactive drugs such as opioids, benzodiazepines and more recently gabapentinoids the class of drugs gabapentin belongs. Pregabalin, the other drug in this group, may have a higher misuse potential than gabapentin due to its rapid absorption and faster onset of action. In the UK, gabapentin use has increased by 350% over five years. In 2016, gabapentin was the 10th most commonly prescribed medication in the United States. This trend is likely due to using gabapentin to avoid the use of opioid analgesics which are strongly addictive. Opioid addiction is a major problem in many countries in the West and also leads to many avoidable deaths from overdose, etc.

Gabapentin was first licensed as an adjunctive treatment for epilepsy in 1993 and later approved for treatment of pain in diabetic neuropathy and post herpetic neuralgia. Diabetic neuropathy is when patients develop pain and uncomfortable sensation in their legs due to nerve damage due to poor control of diabetes. Post herpetic neuralgia is distressing pain that follows herpes zoster (Shingles). However, off-label prescribing (using a drug for other conditions for which it is not licensed by a regulating body like the Food and Drug Administration Authority of USA) of gabapentin increased in 1990s due to extensive marketing campaigns in violation of US Federal regulations, promoting it for use in other pain conditions, and psychiatric disorders. Neuropathic pain can be very difficult to treat with only some 40-60% of people achieving partial relief. In Sri Lanka, too, these drugs are now freely available and the drug market is flooded with so many generic brands. Although we have no published data available, it appears that gabapentin and pregabalin are widely used mostly for off-label indications. It is not uncommon to see our doctors use gabapentin as first line for chronic back pain, headache and other musculoskeletal pains, but there is no evidence to show that it works. Prescribers should be aware that even when used for neuropathic pain over half of those treated with gabapentin do not have worthwhile pain relief but may instead experience adverse effects. So, gabapentin is not a very effective medicine and, therefore, not an essential drug.

The use of gabapentin for non-neuropathic pain is unlicensed and ineffective. Patients inappropriately prescribed gabapentin or pregabalin may not benefit and may be exposed to potential harms, which broadly fall into two categories. First, by causing an adverse drug reaction or toxicity e. g. nervous system effects (headache, visual disturbance, drowsiness, agitation, delirium, lethargy); cardiac effects (rapid heart rate and slowing of heart rate); disturbances in muscle control and movement, and gastrointestinal symptoms. Second, gabapentin or pregabalin prescription may result in drug misuse or diversion (the transfer of any legally prescribed substance from the individual for whom it was prescribed to another person for illicit use.)

We, as prescribers must be conscious of the potential to do harm, both to our patients and society as a whole. Therefore, we must carefully select the patients who will benefit from these drugs. These medicines are licensed to be used in treating neuropathic pain, epilepsy and anxiety, but illicit use of the drugs has increased in recent years. Data from Scotland revealed that gabapentinoids had been prescribed prior to a fifth of drug-related deaths in Scotland in 2016. In this country, too, some medicinal drugs like strong pain killers are abused and a part of the illicit drug trade.

In the UK, from 1 April 2019, gabapentin and pregabalin were made Schedule 3 controlled drugs under the Misuse of Drugs Regulations 2001, and Class C of the Misuse of Drugs Act 1971. Under these regulations prescriptions of gabapentin and pregabalin will be limited to 30 days’ treatment and repeat prescriptions without seeing a doctor will not be issued. Any prescription received have to be dispensed within 28 days. In Sri Lanka, too, it is time to tackle the problem of overuse of gabapentinoids by limiting their use to approved indications. This will bring down the number of prescriptions issued and also the money spent on purchasing or producing this drug.