The Efficacy of MK-8291 in Participants With Post-herpetic Neuralgia (PHN) With Allodynia (MK-8291-012)

Inclusion Criteria: * non-pregnant female (and/or partner) agrees to use two acceptable methods of birth control throughout the trial until 2 weeks after the last dose of treatment * female is postmenopausal or surgically sterile * has a clinical diagnosis of PHN with allodynia for at least 3 months duration after healing of rash * has a body mass index (BMI) =\< 35 kg/m\^2, inclusive * is in good health, with exception of PHN * is on a stable dose for at least 30 days prior to screening if taking any of the following: opioids, non-opioids, paracetomol, non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, antidepressants * is a nonsmoker or has not used nicotine or nicotine containing products for at least prior 3 months Exclusion Criteria: * has a non-PHN chronic pain state * has a history of clinically significant and inadequately treated endocrine, gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory, genitourinary, or major neurological (including stroke and chronic seizures) abnormalities or diseases * has a history of malignant cancer * has a history or presence of esophagitis * has a history of significant multiple and/or severe allergies (e.g. food, drug, latex), or has had an anaphylactic reaction or significant intolerability to prescription or non-prescription drugs or food * is positive for hepatitis B surface antigen, hepatitis C antibodies, or human immunodeficiency virus (HIV) * had major surgery, donated or lost approximately 500 mL of blood within 4 weeks prior to screening * has participated in another investigational trial within 4 weeks prior to screening * has a history of risk factors for Torsades de Pointes, has hypokalemia or hypomagnesemia * has a history or presence of clinically significant cardiac arrhythmia, taking substances with the target of reducing heart rate and or exercising endurance sports * has had an injection of local anesthetics or steroids in the region affected by PHN, within 35 days prior to randomization * anticipates using prescription and non-prescription drugs or herbal remedies during trial * consumes excessive amounts of alcoholic or caffeinated beverages * uses cannabis, any illicit drugs, or has a history of drug (including alcohol) abuse within 12 months of screening visit