Gabapentin Side Effects

by on December 31, 2011


Gabapentin is considered a safe drug, but there will always be a small amount of the population that will experience adverse effects as a result of genetic predispositions, or reactions to the drug itself.  The most common side effects associated with Gabapentin may include drowsiness (or more extreme somnolence), dizziness, weakness, joint pain, nausea and vomiting.

Common Side effects of Gabapentin

The most common Gabapentin Side Effects encountered are generally mild and only self limiting for a short while. These include:

  • Drowsiness
  • Dizziness
  • Fatigue
  • Nausea
  • Joint pain

Gabapentin side effects generally subside after first initial days of treatment, and do not generally warrant cessation of treatment.

Possible Serious Gabapentin side effects

gabapentin As a precaution, it is important to know the possible dangerous Gabapentin side effects that may occur. Although the numbers of patients that experience these are extremely small, they may result in mortality. These include:

  • Increased risk of suicidal tendencies and thoughts, especially in susceptible groups
  • Pneumonia; although the mechanism for this development is unclear it poses a major problem
  • Tachycardia ( abnormal pulse rate)
  • Ovarian failure

If any of these effects should manifest itself, it is critical to contact your health care provider as soon as possible, to minimize risk of complications and discuss if you should commence withdrawal of the drug.

Side effects by systemic classification

Nervous system

These are the most common occurrences to be seen with Gabapentin (Neurontin) use. Side effects including drowsiness (or somnolence), dizziness, ataxia, headache, absence of reflexes, vertigo, hallucinations and syncope are all possible along with the more serious development of suicidal thoughts.

Hematologic (blood system)

Haematological effects commonly encountered include anaemia, thrombocytopenia, increased white blood cell count, non-Hodgkin’s lymphoma, increased bleeding time and purpura. It also happens that sometimes an unexpected decrease in white blood cell count occurs, but is normally associated with concomitant carbamazepine treatment.


It is necessary to differentiate the cardiovascular form the haematological system, as one deals directly with blood, while the other with the mechanisms that support transport of blood. Cardiovascular side effects are uncommon, but when they do appear they may include hypertension or hypotension, palpitations, oedema, angina pectoris (chest pains), heart failure, myocardial infarction (heart attacks), cardiac hypertrophy, hypercholesterolemia and various thrombotic evens (clotting diseases). Although these occur in less than 1% of patients treated with Gabapentin, they cause significant mortality.


Ocular effects are those relating to the eyes, and are another group of the more common possible side effects. Possible adverse reactions may occur as; cataracts, dry eyes, conjunctivitis, eye haemorrhage, glaucoma, blurred vision, eye twitching, or very rarely blindness. Many times it is common for ocular and neural effects to be mistaken, such as hallucinations.


These are the most common manifestation of adverse effects, often caused by allergic reaction to the drug. Commonly eczema, urticaria, dry skin, photosensitivity reactions, skin necrosis (death), seborrhoea, hirsutism (overgrowth of hair), or rarely alopecia (hair loss), may all occur. These effects are hardly ever critical, but may result in loss of self esteem of the patient, as these effects are mainly cosmetic in nature


Related gastrointestinal effects occur in roughly 3% of patients treated with Gabapentin. Not a staggering amount, but a valid proportion of all encountered effects. Included under this system are symptoms such as flatulence, diarrhoea, constipation, peptic ulcer disease, pancreatitis, irritable bowel syndrome and haemorrhoids.


These effects have been surveyed as most worrying for patients, and even though they may not be as serious as they seem, these symptoms significantly decrease patients’ quality of life. Such adverse effects as vaginal pain, urinary incontinence, nocturia (bed wetting),  urinary tract infections plague otherwise happy individuals and cause unnecessary anguish.

Although effects are possible on any body system, these highlight the possible severity of symptoms that may be encountered during Gabapentin treatment. It is always advisable to thoroughly educate yourself before embarking on a drug regimen

Adverse Gabapentin Effects in pregnant women

Gabapentin (Neurontin) has been assigned a pregnancy category of c. C is typically classified as a passing grade. Not so with pharmaceuticals. What this grade implies is that the drug has been demonstrated as Teratogenic (deformity promoting), and fetotoxic (dangerous to the foetus)

Even though these effects have not clearly been demonstrated in pregnant women because of ethical concerns, animal studies positively identify this occurrence. It is best for a pregnant woman to discuss her best course of action with her doctor, with the same implication for breastfeeding mothers. It should only be continued once the benefits clearly outweigh the risk to the child.