Inclusion Criteria:

- Age >/= 18

- Diagnosis of cancer

- Willing and able to give informed consent to the CIN-E study and complete study
questionnaires, this involves adequate understanding of written and spoken English
(translators will not be used)

- Chemotherapy-induced painful peripheral neuropathy as diagnosed by score of >12 on
the Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) with a pain
intensity rating of >4, on a 11 point numeric rating scale (0= no pain, 10= worst
possible pain).

- Duration of chemotherapy-induced painful peripheral neuropathy >4 weeks. Participant
may either have completed chemotherapy, or be receiving ongoing chemotherapy.

- Able to attend research centre according to the required visit schedule.

- Diet allows bovine gelatine (present in both ethosuximide and placebo capsules)

- Women of child-bearing potential must be using a reliable form of contraception i.e.
oral contraceptives, a barrier method (condom or diaphragm), intra-uterine device or
abstinence.

Exclusion Criteria:

- Renal impairment (serum creatinine >1.5x normal level)

- Deranged liver function (AST>3x normal level)

- Patients currently taking any anti-depressant medication, for example fluoxetine,
paroxetine, citalopram, venlafaxine, amitriptyline, or within the past week.

- Patients currently taking any other anti-epileptic drug, including gabapentin, or
within the past week.

- Pregnancy

- Allergy to succinimides, ethosuximide, methsuximide, phensuximide. Pre-exisitng
painful peripheral neuropathy of any other cause.