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High yield illustrated pharmacology notes of gabapentin side effects, mechanism of action, clinical uses, drug interaction, pharmacokinetics

Overview

Gabapentin is an amino acid, an analog of GABA, that is effective against partial seizures.

Gabapentin was originally planned as a spasmolytic but it was found to be more effective as an antiseizure drug.

Pregabalin is another GABA analog and closely related to gabapentin. This drug has been approved for both antiseizure activity and for its analgesic properties.

Gabapentin Mechanism of action

Gabapentin does not act directly on GABA receptors in spite of their close structural resemblance to GABA.

They may, however, modify the synaptic or nonsynaptic release of GABA. An increase in brain GABA concentration is observed in patients receiving gabapentin.

Gabapentin is transported into the brain by the L-amino acid transporter.

Gabapentin binds avidly to the alpha-2-delta subunit of voltage-gated Ca2+ channels.

This appears to underlie the main mechanism of action, which is decreasing Ca2+ entry, with a predominant effect on presynaptic N-type channels.

A decrease in the synaptic release of glutamate provides the antiepileptic effect.

In addition, gabapentin may exert an analgesic effect by activating descending inhibitory noradrenergic pathways that regulate neurotransmission of pain signals in the dorsal horn of the spinal cord. (Ref)

Gabapentin mechanism of action
Gabapentin mechanism of action

Points to Remember

Gabapentin has no activity at GABAA or GABAB receptors of GABA uptake carriers of brain

Pharmacokinetics

Gabapentin is not metabolized and does not induce hepatic enzymes.

Absorption is nonlinear and dose-dependent at very high doses, but the elimination kinetics are linear.

Gabapentin does not bind to plasma proteins and is excreted unchanged through the kidneys.

Reduced dosing is required in renal disease

Half-life is 5-8 hours

Clinical uses of Gabapentin

Gabapentin is effective as an adjunct against partial seizures and generalized tonic-clonic seizures

Gabapentin is considered to be a first line drug for neuralgic pain due to diabetic neuropathy and postherpetic neuralgia.

It has some prophylactic effect in migraine and is an alternative drug for phobic states

It is also helpful to reduce pain related to multiple sclerosis

Gabapentin is also approved for the treatment of Bipolar disorder and Generalized anxiety disorder

Gabapentin uses mnemonic
Gabapentin uses mnemonic

Points to remember

  • Gabapentin increases GABAergic transmission by increasing its synthesis and release.
  • Its absorption from GIT is saturable, therefore it is safe even after overdosing

Gabapentin side effects

Dizziness and drowsiness

Somnolence

Fatigue

Weight gain

Uncoordinated movement

Dry mouth

Behavioural changes

Suicidal thoughts

Breathing difficulties with opioids and other CNS depressants

What type of drug is gabapentin?

Gabapentin is an anticonvulsant group of drug. Gabapentin decreases abnormal excitement in brain and helps to treat seizures. Gabapentin is the drug of choice for post herpetic neuralgia related pain.

Does gabapentin make you gain weight?

Weight gain and uncoordinated movement are possible side effects of gabapentin

What drugs cannot be taken with gabapentin?

Gabapentin can interact with Losartan, ethacrynic acid, phenytoin, mefloquine, magnesium oxide, cimetidine, naproxen, morphine and caffeine. Gabapentin use is contraindicated in patients with myasthenia gravis or myoclonus.

Is gabapentin a steroid?

Gabapentin is not a steroid. It is used as an anticonvulsant, sedative and anxiolytic to treat chronic pain syndromes, including neuropathic pain.

Is gabapentin an anti inflammatory for dogs?

Gabapentin is used in dogs to treat chronic pain, particularly of neuropathic origin. It appears to be most effective when combined with other types of analgesic agents like NSAIDs

Is gabapentin an anti inflammatory for cats?

Gabapentin is used in cats to treat chronic pain, particularly of neuropathic origin. It appears to be most effective when combined with other types of analgesic agents like NSAIDs

Reference:

Basic and Clinical Pharmacology; Bertram G. Katzung; 14th ed

The Pharmacological Basis of Therapeutics; Goodman & Gilman’s; 13th ed

Essentials of Medical Pharmacology; KD Tripathi; 7th ed

Visual Book Of Pharmacology, Microbiology, Pathology and Immunology (Medical Mnemonics); Nazmul Alam; 1st ed

Review of Pharmacology; Garg & Gupta; 14th ed


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