Anticonvulsants

Gabapentin and pregabalin — mixed evidence. "Anticonvulsants (gabapentin, pregabalin) have shown mixed results," though "a Cochrane review examining multiple studies did feel that the combined results favored Gabapentin over placebo."

[Trigeminal neuralgia] First-line — carbamazepine. NHS: carbamazepine "is the first treatment usually recommended to treat trigeminal neuralgia"; "only carbamazepine is approved by the United States Food and Drug Administration (FDA) for treating trigeminal neuralgia." It "needs to be taken several times a day to be effective" — "Neither medication provides immediate relief"; the label: "This drug is not a simple analgesic." Stop "slowly, over days or weeks." Oxcarbazepine is an alternative with fewer interactions; "Both medications can cause hyponatremia." Carbamazepine reduces hormonal contraceptive effect ("Alternative or back-up methods of contraception should be considered"), "can cause fetal harm," and causes drowsiness — caution with alcohol and driving.

A first-line mood stabiliser for mania — with one boxed fetal-risk restriction and one common error. On the CANMAT/ISBD and WFSBP first-line lists for acute mania, as reported by StatPearls, divalproex/valproate stands alongside lithium, and "lithium or valproate plus an antipsychotic" is the usual combination for severe mania, psychosis or an inadequate response. StatPearls notes that "differences exist among guidelines," so these are the carrier’s synthesis, not one society’s rule. The mechanistic reason anticonvulsants belong on a mood-disorder drug list is sourced: "newer research indicates altered intracellular calcium signaling occurs in people with bipolar disorders, and antiseizure medications can provide effective treatment." Carbamazepine sits in the same historical group. The pregnancy rule, from the FDA label: "valproate should not be used to treat women with epilepsy or bipolar disorder who are pregnant or who plan to become pregnant unless other medications have failed to provide adequate symptom control or are otherwise unacceptable," because in-utero exposure causes neural tube defects, other major malformations and decreased IQ; StatPearls adds that it "should generally be avoided in women of childbearing potential unless no suitable alternatives exist and effective contraception is ensured." Never present "lithium or valproate" as an even choice for a patient of childbearing potential without that restriction attached. The common error is lamotrigine. It belongs on the depressive side of bipolar disorder — named in combination with lithium for acute bipolar depression, and among the mood stabilisers to which an antidepressant may be added — but a meta-analysis found that "gabapentin, lamotrigine, and topiramate showed no difference when compared to placebo for treating mania." Lamotrigine does not treat acute mania, and gabapentin and topiramate have no sourced role in bipolar disorder at all. On comparative efficacy in acute mania, the sourced ranking is honest about hierarchy: atypical antipsychotics outperformed mood stabilisers for the acute episode, with valproic acid, carbamazepine and ziprasidone more effective than placebo but less so than risperidone, olanzapine, haloperidol, lithium, quetiapine and aripiprazole.

"The use of anticonvulsants is mandatory for patients with seizures" (NCI); NINDS: "Anticonvulsants to treat or prevent seizures." After craniotomy, the post-op bundle includes "Seizure prophylaxis," and "Levetiracetam is superior to phenytoin for de novo seizures following craniotomy" (StatPearls).

Topiramate — an option in bulimia, not first-line. It "has shown a reduction in binge episodes, but the side effects should be carefully monitored, especially weight loss and cognitive problems" — weight loss being an unwelcome effect in an eating disorder.

Seizures. NINDS: "Anticonvulsants can stop or prevent seizures." StatPearls: "Seizures may need to be managed with valproic acid or phenytoin. For status epilepticus, one may require benzodiazepines." Seizures are also the most common long-term complication.

First-line, especially with poor sleep. "Patients with widespread pain and significant sleep disturbances should use pregabalin as a first-line option" (StatPearls); LYRICA is labeled for "Management of fibromyalgia" in adults. "Gabapentin is a suitable alternative when cost or availability limits pregabalin use." Watch for angioedema, respiratory depression with opioids or other CNS depressants, dizziness and somnolence, edema and weight gain; taper over at least a week.

[PHN] First-line systemic pain treatment. "Pharmacologically, first-line systemic treatments consist of anticonvulsants such as gabapentin and pregabalin." Both "require careful dose titration and monitoring for adverse effects such as sedation and cognitive impairment"; with reduced renal function, start "at a lower dose and titrated upward more slowly."

Seizure prophylaxis for 7 days only: seizure prophylaxis is recommended for 7 days following severe TBI, and levetiracetam is often preferred for its dosing profile and lower incidence of adverse events. In the acute phase a seizure with altered consciousness is itself an impending-herniation red flag.

Uncertain — "The effectiveness of anticonvulsants such as gabapentin and topiramate is uncertain."

Prevention: valproate or topiramate, especially for people who also have epilepsy. StatPearls advises: "Avoid valproate in women of childbearing age and topiramate during pregnancy." Topiramate doses above 100 mg/day may alter the effect of oral contraceptives.

Adjuvants for neuropathic pain. StatPearls: initial treatment "typically involves gabapentin or pregabalin." Open RN names gabapentin as an adjuvant that adds to, or works independently of, opioid analgesia.

[Pregabalin] FDA-indicated for "Neuropathic pain associated with diabetic peripheral neuropathy (DPN)"; gabapentin is also used (StatPearls, NIDDK). "LYRICA may cause dizziness and somnolence" that can impair driving. "Respiratory depression: May occur with LYRICA, when used with concomitant CNS depressants." Causes peripheral edema — "Exercise caution when co-administering LYRICA and thiazolidinedione antidiabetic agents." Angioedema can cause "life-threatening respiratory compromise requiring emergency treatment. Discontinue LYRICA immediately in these cases." "Taper LYRICA gradually over a minimum of 1 week"; dose adjusted for kidney impairment.

The mainstay of chronic epilepsy: monotherapy first, titrated to effect and toxicity, with the drug matched to the seizure type — ethosuximide is first-line for absence (where phenytoin and carbamazepine actually worsen seizures), valproate is the classic broad-spectrum choice for generalized epilepsies but is contraindicated in pregnancy, and tonic-clonic first-line options include valproate, lamotrigine, and topiramate. Medication controls seizures — up to 70% of patients could become seizure-free — but does not cure the disorder, and a first unprovoked seizure with a normal neurological baseline often doesn’t require starting one at all.

Common culprits — "lamotrigine, carbamazepine, phenytoin, valproic acid, phenobarbital." Tegretol boxed warning: SJS/TEN risk is "ABOUT 10 TIMES HIGHER" in some Asian countries; screen for HLA-B*1502 in at-risk ancestry before starting; over 90% of cases occur "within the first few months of treatment"; stop at the first rash. Lamictal boxed warning: serious rash in "0.3% to 0.8% in pediatric patients" and "0.08% to 0.3% in adults"; risk rises with valproate or exceeding the starting dose or escalation; nearly all cases "within 2 to 8 weeks"; "Do not restart LAMICTAL in patients who discontinued due to rash unless the potential benefits clearly outweigh the risks."

Seizures after SAH. Seizures occur in fewer than 10%; StatPearls lists "seizure prophylaxis" among ICU interventions for poor-grade patients (an older-guideline relay) and seizure prophylaxis after discharge. Interaction: the enzyme-inducing anticonvulsants carbamazepine, phenobarbital and phenytoin can markedly lower nimodipine levels and efficacy — the nimodipine label advises avoiding the combination.

Potent pain control via µ-opioid receptor agonism. Watch for respiratory depression; reverse with naloxone.

Potentiate GABA for anxiety, seizures, and sedation. Additive CNS depression — deadly with opioids.

First-line antidepressants that raise synaptic serotonin. Delayed onset; watch for serotonin syndrome and early suicidality.

A widely used fever/pain reliever with no anti-inflammatory or platelet effect — but hepatotoxic in overdose.

Dopamine-blocking drugs for psychosis. Watch EPS, NMS, metabolic effects — boxed warning in elderly dementia.

Lithium controls bipolar mania but has a tiny therapeutic window — levels are everything.