Table 2.

Medications for Postherpetic Neuralgia

Characteristic	Lidocaine patch	Gabapentin	Nortriptyline	Opioids	Pregabalin	Tramadol
Structure	Amino amide anesthestic	Gamma-aminobutyric acid (GABA) analog	Dibenzocycloheptene tricyclic antidepressant (TCA)	Mu opioid receptor agonist	Gamma-aminobutyric acid (GABA) analog	Mu opioid agonist and serotonin and norepinephrine reuptake inhibitor
Kinetics	Very little systemic absorption	Renal elimination; prolonged half-life with renal impairment	Hepatic metabolism; higher levels of active metabolites in the elderly	Hepatic metabolism and renal elimination	Renal elimination; prolonged half-life with renal impairment	Hepatic metabolism and renal elimination
Standard Dosing	Up to 3 patches applied over the affected area for 12 hours a day	Start at 100-300 mg at night; increase by 100-300 mg a day every 1-7 days as tolerated in tid dosing; maximum dose 3600 mg/day	Start 10 mg at night; increase by 10 mg every 4-7 days by the same amount until reduction in pain; maximum dose 75-150 mg day	In morphine equivalents start 2.5-15 mg every four hours; after 1-2 weeks, convert total daily dosage to long-acting opioid analgesic and continue short-acting medication as needed	150 mg/day given in 2 or 3 divided doses; may increase to 300 mg/day, given in 2 or 3 divided doses, within 1 week; maximum dosage 600 mg/day	Start 50 once daily; increase by 50 mg daily in divided doses every 3-7 days as tolerated; maximum dose 400 mg daily; in patients over 75 years of age, 300 mg daily in divided doses
Benefit: % Significant Improvement*	≥50% reduction in pain scores: 31% lidocaine patch vs. 8% placebo patch	Moderate or much pain improvement: 41-43% gabapentin vs. 12-23% placebo	Moderate to good pain relief: 44-67% TCAs vs. 5-19% placebo or control drug	Masked preference: 67% oxycodone vs. 11% placebo	≥50% reduction in pain scores: 50% pregabalin vs. 20% placebo	≥50% reduction in pain scores 77% tramadol vs. 56% placebo
Adverse Events	Skin redness or rash	Somnolence, dizziness, ataxia, peripheral edema	Arrhythmia, cardiac conduction block, orthostatic hypotension, urinary retention, constipation, cognitive impairment	Constipation, sedation, nausea/vomiting, respiratory depression, nervous system symptoms, pruritis	Somnolence, dizziness, ataxia, peripheral edema	Constipation, sedation, nausea/vomiting, respiratory depression, nervous system symptoms, seizures
Main Drug-Drug Interactions	Class I antiarrythmics	Opioids	Antipsychotics, anticholinergics, selective serotonin reuptake inhibitors (SSRI), sedative-hypnotics, antiarrhythmics, MAO inhibitors	Anticholinergics, sedative-hypnotics, anxiolytics, CYP2D6 inhibitors, TCAs, muscle relaxants	Opioids	Anticholinergics, sedative-hypnotics, anxiolytics, CYP2D6 inhibitors, SSRIs, TCAs, muscle relaxants
Main Drug-Disease Interactions	None	Dementia, ataxia, falls	Myocardial infarction, QT prolongation, AV block, bundle branch block, ileus, prostatic hypertrophy, seizure disorder, glaucoma, dementia	Ileus, chronic obstructive pulmonary disease, dementia, prostatic hypertrophy	Dementia, ataxia, falls	Ileus, chronic obstructive pulmonary disease, dementia, prostatic hypertrophy, seizure disorder
How Supplied	10 by 14 cm. lidocaine patch contains 5% lidocaine base on polyester backing	100 mg, 300 mg, 400 mg capsules; 600 mg, 800 mg tablets	10 mg, 25 mg, 50 mg, 75 mg capsules; 10 mg/5ml solution	Multiple drugs and dosage forms	25 mg, 50 mg, 75 mg, 100 mg, 150 mg, 200 mg, 225 mg, 300 mg capsules	50 mg tablet