Anticonvulsants

Drug	Dosage	Remarks
Carboxamides
Carbamazepine	Painful diabetic neuropathy: 200 mg PO 6-12 hourly Trigeminal neuralgia: Initial dose: 200-400 mg PO 24 hourly Increase dose slowly until pain-free then gradually decrease dosing to the lowest possible maintenance level Max dose: 1.2 g/day	Adverse Reactions May decrease side effects by starting at a low dose and increasing slowly CNS effects (dizziness, drowsiness, ataxia, paresthesia, headache); GI effects (dry mouth, abdominal pain, nausea/vomiting, diarrhea, anorexia, constipation); Dermatologic effects (rash which may be severe, photosensitivity reactions, Stevens-Johnson syndrome [SJS], systemic lupus erythematosus [SLE]); Hematologic effects (agranulocytosis, eosinophilia, aplastic anemia, leukopenia, leukocytosis, thrombocytopenia and purpura); Other effects (abnormalities of kidney and liver function, splenomegaly, lymphadenopathy, hyponatremia, edema, arrhythmias, heart block, heart failure) Risk of developing anemia or agranulocytosis is increased 5-8x greater during treatment compared to general population Can potentially cause or exacerbate syndrome of inappropriate antidiuretic hormone secretion (SIADH) or hyponatremia Special Instructions When pain relief is obtained, gradually discontinue therapy until another attack occurs Should be taken with food Avoid grapefruit juice Avoid in patients with AV block, history of bone marrow depression, history of acute intermittent porphyria Use with caution in patients with cardiac, hepatic, renal disease or history of blood disorders Liver function tests (LFTs), urinalysis, blood urea nitrogen (BUN), serum Na, complete blood count (CBC) should be performed prior to and periodically during the treatment Discontinue treatment if significant bone marrow depression develops Fluid restriction is indicated if with symptomatic hyponatremia or discontinuation of treatment should be considered HLA-B*1502 genetic testing is recommended to be done before starting therapy especially in patients of Asian descent; if positive, weigh in if benefit clearly outweighs risk of having SJS and toxic epidermal necrolysis (TEN)
Hydantoin
Phenytoin	Initial dose: 100 mg PO 8 hourly May increase gradually to 200 mg 8 hourly if necessary Max dose: 600 mg/day	Adverse Reactions Side effects may decrease with dose reduction or continued administration GI effects (nausea/vomiting, abdominal pain and lack of appetite); CNS effects (headache, dizziness, insomnia); Other effects (hirsutism, gum tenderness, gingival hyperplasia, coarsening of facial features, mild hypersensitivity with skin rash [typically erythema multiforme with fever]) Prolonged administration may result in subtle changes in mental function and cognition; rickets and osteomalacia have occurred & may have been caused by interference of Vitamin D and folate metabolism Phenytoin toxicity may result in nystagmus, diplopia, slurred speech, ataxia, confusion and hyperglycemia Rarely SJS, SLE or erythema multiforme, blood disorders eg thrombocytopenia, leukopenia, etc may occur Special Instructions Use with caution in patients with liver dysfunction, DM, elderly Assess compliance or possible toxicity by routine Phenytoin serum level monitoring during dose adjustment Therapeutic serum concentration: 40-80 mmol/L Monitor for signs of blood or skin toxicity; patient should inform physician immediately if signs of blood toxicity occur eg fever, sore throat, bruising, skin rash, etc
Other Anticonvulsants
Gabapentin	Initial dose: Day 1: 300 mg PO 24 hourly Day 2: 300 mg PO 12 hourly Day 3: 300 mg PO 8 hourly Based on patient response and tolerability, may increase dose in increments of 300 mg/day every 2-3 days up to a max dose of 3,600 mg/day Max dose: 3.6 g/day	Adverse Reactions CNS effects (somnolence, dizziness, ataxia, nystagmus, headache, tremor, diplopia, amblyopia); Other effects (fatigue, nausea and/or vomiting) Special Instructions Use with caution in patients with history of psychotic illness, renal impairment Discontinuation and/or addition or substitution of alternative therapy should be gradual over at least 1 week May affect patients ability to drive or operate machinery
Pregabalin	Initial dose: 150 mg/day PO divided 8-12 hourly May be increased to 300 mg/day after a 3- to 7-day interval May increase further to max dose after another 7-day interval Max dose: 600 mg/day	Adverse Reactions CNS effects (somnolence, dizziness, confusion, euphoric mood, ataxia, attention disturbance, abnormal coordination, memory impairment, tremor, dysarthria, paresthesia, blurred vision, diplopia, vertigo, dry mouth, increased appetite, decreased libido, erectile dysfunction, irritability); GI effects (constipation, vomiting, flatulence); Other effect (fatigue) Special Instructions Use with caution in patients with galactose intolerance, lactase deficiency or glucose-galactose malabsorption, renal impairment, DM May affect patients ability to drive or operate machinery

Antidepressants*

Drug	Dosage	Remarks
Serotonin & Norepinephrine Reuptake Inhibitors (SNRIs)
Duloxetine	60 mg PO 24 hourly Max dose: 120 mg/day	Adverse Reactions CNS effects (somnolence, dizziness, insomnia, nervousness, anorexia, anxiety); GI effects (constipation, diarrhea, nausea, xerostomia); Other effects (abnormal dreams, yawning, tremor, blurred vision, increased sweating, weight loss, sexual dysfunction) Dose-related: Vasodilation, hypertension Special Instructions Start with low dose to minimize side effects and titrate upward to the desired response Use with caution in renal and hepatic impairment Do not stop medication abruptly; taper dose over several weeks
Tricyclic Antidepressants (TCAs)
Amitriptyline	Initial dose: 10-25 mg PO at bedtime Increase dose by 25 mg/day to max dose on a weekly interval Max dose: 150 mg/day	Adverse Reactions Side effects are mostly due to antimuscarinic actions and may be decreased if started at low dose and increased gradually Dry mouth, constipation (may lead to paralytic ileus), blurred vision, increased intraocular pressure, urinary retention, hyperthermia, drowsiness can occur, nervousness, insomnia, headache, peripheral neuropathy, ataxia, tremor, confusion/delirium can occur especially in older patients, nausea/vomiting, gastric irritation, hypotension, tachycardia, sweating, weight gain Special Instructions Start with a low dose to minimize side effects and titrate upward to the desired response Total daily dose should be given at bedtime Use with caution in patients with urinary retention, prostatic hyperplasia, chronic constipation, untreated angle-closure glaucoma, patients with CV disease, history of epilepsy, DM, impaired hepatic function Not recommended for elderly patients and those with CV disease Do not stop medication abruptly; taper dose over several weeks
*Antidepressant therapy in children, adolescents and young adults is associated with clinical worsening, suicidality or unusual changes in behavior. Close observation of the patient and communication with the prescribing physician are warranted.

Drugs for Neuropathic Pain

Drug

Dosage

Remarks

Mirogabalin

Initial dose: 5 mg PO 12 hourly, then increase dose by 5 mg/dosing with at least 1 week interval up to 15 mg 12 hourly
May increase or decrease dose between 10 mg and 15 mg 12 hourly

Adverse Reactions

CNS effects (somnolence, dizziness); Other effects (constipation, edema, gait disturbance, increased weight and hepatic enzyme)

Special Instructions

Use with caution in patients with hepatic function disorder
Potential occurrence of obesity, measure weight regularly; ophthalmic disorders; withdrawal symptoms (eg insomnia, nausea, diarrhea, decreased appetite) with abrupt treatment discontinuation
Women of childbearing potential should use effective contraception
Not to operate potentially dangerous machinery

Thioctic acid (α-lipoic acid)¹

600 mg PO 24 hourly or
600 mg slow IV infusion 24 hourly x 2-4 weeks or several times/week

Adverse Reactions

GI effects (nausea/vomiting, stomach and intestinal pain, diarrhea); CNS effects (vertigo, headache); Dermatologic effects (rash, urticaria, itching); Other effects (sweating, visual disturbances)

Special Instructions

Should be taken 30 minutes before meals
- Swallow whole, do not chew or crush
Monitor glucose levels in urine and blood regularly
- May potentiate hypoglycemic effect of insulin or oral antidiabetics
Advise patient to avoid alcohol intake

¹Various combination products are available. Please see the latest MIMS for specific formulations and prescribing information.

Muscle Relaxant (Centrally Acting)

Drug

Dosage

Remarks

Baclofen

Start with 5 mg PO 8 hourly for 3 days,
Increase to 10, 15 and 20 mg 8 hourly at 3-day intervals
Max dose: 80 mg/day

Adverse Reactions

CNS effects (daytime sedation and drowsiness, mental confusion, dizziness, personality changes, vertigo, headache, insomnia, euphoria, depressive state, ataxia, tremor, nystagmus, accommodation disorders, hyperhidrosis); CV effects (hypotension, diminished CV function); GI effects (nausea/vomiting, constipation, diarrhea, retching, dry mouth), Respiratory effect (respiratory depression); Other effects (myalgia, weakness, lassitude, exhaustion, hallucination, nightmares, tinnitus, rash, pruritus, dysuria, frequency of micturition)

Special Instructions

Use with caution in patients with impaired renal function, stroke, convulsive disorders, peptic ulceration, elderly patients with cerebrovascular disorders, respiratory, hepatic or renal failure, underlying bladder sphincter hypertonia, psychiatric disorders
Avoid abrupt discontinuation

Opioids

Drug	Dosage	Remarks
Morphine	5-20 mg IM/SC 4 hourly as needed	Adverse Reactions Respiratory effect (hypoventilation); CNS effects (dizziness, somnolence, confusion, hallucination, euphoria); GI effects (constipation, nausea/vomiting, dry mouth) Special Instructions Contraindicated in patients with respiratory depression, obstructive airway disease, acute hepatic disease and paralytic ileus May cause dependence on long-term use
Tapentadol	Extended-release: 50 mg PO 12 hourly Max dose: 500 mg/day	Adverse Reactions CNS effects (dizziness, headache, drowsiness, fatigue, anxiety, insomnia); GI effects (nausea/vomiting, constipation, diarrhea, xerostomia, dyspepsia, decreased appetite); Dermatologic effects (pruritus, hyperhidrosis) Special Instructions Contraindicated in patients with respiratory depression, acute or severe asthma, GI obstruction or suspected paralytic ileus Not to be used with or within 14 days of monoamine oxidase (MAO) inhibitors
Tramadol¹	Regular-release: 50-100 mg PO 4-6 hourly Extended-release: 100-200 mg PO 12 hourly May be titrated to 150-200 mg PO 12 hourly for pain relief Max dose: 400 mg/day	Adverse Reactions CNS effect (dizziness); GI effects (dry mouth, vomiting); CV effect (vasodilation); Other effect (sweating) Special Instructions An increase risk in seizures may occur in patients taking other medications which decrease the seizure threshold Use with caution in patients with history of opioid dependence, seizures or at risk for seizures, increased intracranial pressure May cause dependence on long-term use
¹Combinations of Tramadol and Paracetamol are available. Please see the latest MIMS for specific formulations and prescribing information.

Topical Agents

Drug	Available Strength	Dosage	Remarks
Anesthetic
Lidocaine (Lignocaine)	5% patch	3 patches/day for a max of 12 hours	Adverse Reactions Mild local reactions (itching, erythema, edema) Rarely methemoglobinemia Special Instructions Do not use for >12 hours in a 24-hour period
Other Agent
Capsaicin	0.0125% lotion, gel 0.025% lotion, gel 0.075% cream, gel, lotion	Apply 6-8 hourly	Adverse Reactions Local irritation and erythema Other application site reactions include pruritus, papules and edema Special Instructions Before applying the Capsaicin patch, treat the affected area and 1-2 cm of the surrounding area with local anesthetic
	0.31% gel	Apply 8-12 hourly
	8% dermal patch	Apply up to 4 patches/application for 30 minutes Repeat no more frequently than every 3 months

Vitamin B-Complex/With C

Drug	Dosage		Remarks
Benfotiamine¹	Initial dose: 150 mg PO 8-12 hourly for at least 3 weeks Maintenance dose: 150-300 mg PO 24 hourly		Adverse Reactions Rarely, hypersensitivity reactions (skin eruptions, urticaria, anaphylactic reactions)
Mecobalamin¹	0.5 mg PO 8 hourly or 0.5 mg IM/IV 3x/week		Adverse Reactions Oral: Loss of appetite, nausea/vomiting, diarrhea, GI upset Injection: Hypersensitivity reactions, pain, induration at IM sites, headache, sweating
Drug	Available Strength	Dosage	Remarks
Combination Products
Vitamin B₁, B₆, B₁₂¹	Vitamin B₁ 250 mg, B₆ 250 mg, B₁₂ 1,000 mcg	Initial dose: 2-3 tab/day PO x 7-10 days Maintenance dose: 1 tab PO 24 hourly	Adverse Reactions GI effects (nausea/vomiting, abdominal pain, diarrhea); Hypersensitivity reactions (sweating, tachycardia, pruritus, urticaria) Special Instructions Use with caution in patients with allergy to cobalamins, intolerance to thiamine, sugars (ie glucose-galactose malabsorption, Lapp lactase deficiency, sucrose-isomaltase insufficiency)
	Vitamin B₁ 100 mg, B₆ 200 mg, B₁₂ 200 mcg	Initial dose: 1 tab PO 8-24 hourly Maintenance dose: 1 tab PO 24 hourly
	Vitamin B₁ 100 mg, B₆ 100 mg, B₁₂ 5,000 mcg	2-4 tab/day PO in divided doses or 1 tab PO 24 hourly
	Vitamin B₁ 100 mg, B₆ 100 mg, B₁₂ 5,000 mcg	1 amp IM 24 hourly Follow-up therapy/milder cases: 2-3 amp/week
¹Various combination products are available. Please see the latest MIMS for specific formulations and prescribing information.

Disclaimer

All dosage recommendations are for non-pregnant and non-breastfeeding women, and non-elderly adults with normal renal and hepatic function unless otherwise stated.
Not all products are available or approved for above use in all countries.
Products listed in the Drug Summary are based on indications stated in the locally approved product monographs.
Please refer to local product monographs in Related MIMS Drugs for country-specific prescribing information.

Neuropathic Pain Tóm tắt về thuốc

Anticonvulsants

Antidepressants*

Drugs for Neuropathic Pain

Muscle Relaxant (Centrally Acting)

Opioids

Topical Agents

Vitamin B-Complex/With C

Disclaimer

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