The white pill imprinted with D 24 (or debossed with D and 24 on either side of the bisect) is Gabapentin 600 mg, an anticonvulsant and neuropathic pain medication.
Pill Identification
Attribute – Details
- Imprint – D 24 (or D and 24 separated by a score line)
- Active Ingredient – Gabapentin (600 mg)
- Color & Shape – White, oval / elliptical, film-coated tablet
- Scoring – Bisected with a deep break line on both sides
- Size – Approximately 17 mm
- Manufacturer / Labeler – Aurobindo Pharma USA, Inc.
- Drug Class – Gabapentinoids / Anticonvulsants
- Controlled Status – Non-controlled federally (prescription only; tracked in some state prescription monitoring programs)
Mechanism of Action
Despite being a structural analogue of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), gabapentin does not bind to receptors, nor does it alter GABA uptake or metabolism.
- Subunit Binding: Gabapentin exerts its primary pharmacologic effect by binding with high affinity to the auxiliary subunits of voltage-gated calcium channels in presynaptic central nervous system neurons.
- Reduction of Neurotransmitter Release: By binding to these calcium channel subunits, gabapentin decreases calcium influx at nerve terminals. This attenuates the downstream synaptic exocytosis of excitatory neurotransmitters—including glutamate, substance P, and calcitonin gene-related peptide (CGRP).
- Net Effect: Dampening central sensitization and hyper-excitability, producing antinociceptive (pain-relieving) and anticonvulsant effects.
Indications & Clinical Dosage
Gabapentin 600 mg is indicated for:
- Postherpetic Neuralgia (PHN): Pain following shingles in adults.
- Partial-Onset Seizures: Adjunctive therapy in the treatment of partial-onset seizures, with or without secondary generalization.
- Off-Label Uses: Diabetic peripheral neuropathy, fibromyalgia, restless legs syndrome, and generalized anxiety.
Typical Adult Dosing Regimens
- Postherpetic Neuralgia: Initiated with a titration schedule: Day 1 (300 mg once daily), Day 2 (300 mg twice daily), Day 3 (300 mg three times daily). Titrated as needed up to 1800 mg/day (administered as 600 mg three times daily).
- Epilepsy / Seizures: Maintenance dose typically ranges from 900 mg to 2400 mg/day, divided evenly across three daily doses. The maximum interval between doses should not exceed 12 hours.
- Renal Dose Adjustment: Because gabapentin is eliminated almost entirely by renal excretion unchanged, dosage must be modified based on creatinine clearance :
Creatinine Clearance – Total Daily Dose Range
- 900–3600 mg/day (divided into 3 doses)
- 400–1400 mg/day (divided into 2 doses)
- 200–700 mg/day (single daily dose)
- 100–300 mg/day (single daily dose, adjusted proportionally)
- Hemodialysis – Supplemental post-dialysis dose required
Side Effects
Common Side Effects
- Drowsiness & Somnolence
- Dizziness & Lightheadedness
- Ataxia & Coordination Problems
- Peripheral Edema (swelling of extremities)
- Fatigue & Asthenia
- Weight Gain
Severe / Rare Adverse Reactions
- Severe Respiratory Depression: Especially when combined with central nervous system (CNS) depressants or opioids.
- Anaphylaxis & Angioedema: Swelling of the throat, tongue, or lips causing airway obstruction.
- Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): Multiorgan hypersensitivity presenting with fever, rash, and lymphadenopathy.
- Suicidal Ideation & Behavior: Emergence or worsening of depression, mood changes, or suicidal thoughts.
Precautions & Drug Interactions
- CNS Depressants & Opioids: Concurrent use with opioids (e.g., oxycodone, morphine), benzodiazepines, or alcohol causes additive CNS and respiratory depression, significantly elevating the risk of fatal overdose.
- Antacids: Aluminum and magnesium antacids reduce gabapentin bioavailability by approximately 20%. Take gabapentin at least 2 hours after antacid administration.
- Renal Monitoring: Renal function should be evaluated prior to initiating treatment and monitored periodically in elderly or compromised patients.
- Pregnancy & Lactation: Classified as Pregnancy Category C; excreted into human breast milk. Use only if benefits justify potential risks to the fetus or infant.
Critical Warnings
- Do Not Stop Abruptly: Discontinuing gabapentin suddenly may precipitate withdrawal symptoms (anxiety, insomnia, nausea, sweating, pain) and can trigger status epilepticus or rebound seizures in patients with epilepsy. It must be tapered gradually over at least 1 week.
- Cognitive & Motor Impairment: Gabapentin causes significant somnolence and dizziness; patients should avoid driving, operating machinery, or performing hazardous tasks until tolerance is established.
- Respiratory Compromise Warning: The FDA warns of serious breathing difficulties in patients using gabapentin who have underlying respiratory risk factors (such as COPD) or who use opioid pain medications concurrently.