The risk of liver inflammation is associated with the duration of treatment and the daily dose. In patients treated for hyperthermia, no liver toxicity has been observed so far. Patients on chronic dantrolene therapy should routinely have LFTs monitored.Pleural effusion with inflammation of the fibrous sac around the heart (oral treatment only), rare cases of bone marrow damage, diffuse muscle pains, backache, dermatologic reactions, transient cardiovascular reactions, and crystals in the urine have additionally been seen. Muscle weakness may persist for several days following treatment. Mutagenicity and carcinogenity
It is unclear whether dantrolene has carcinogenic effects. Contraindications
Oral dantrolene cannot be used by:
people with a pre-existing liver disease
people with compromised lung function
people with severe cardiovascular impairment
people with a known hypersensitivity to dantrolene
pediatric patients under five years of age
people who need good muscular balance or strength to maintain an upright position, motoric function, or proper neuromuscular balanceIf the indication is a medical emergency, such as malignant hyperthermia, the only significant contraindication is hypersensitivity. Pregnancy and breastfeeding
If needed in pregnancy, adequate human studies are lacking, therefore the drug should be given in pregnant women only if clearly indicated. It may cause hypotonia in the newborn if given closely before delivery.Dantrolene should not be given to breastfeeding mothers. If a treatment is necessary, breastfeeding should be terminated. Interactions
Dantrolene may interact with the following drugs:
Calcium channel blockers of the diltiazem/verapamil type: Intravenous treatment with dantrolene and concomitant calcium channel blocker treatment may lead to severe cardiovascular collapse, abnormal heart rhythms, myocardial depressions, and high blood potassium.
Notalgia paresthetica or Notalgia paraesthetica (NP) (also known as "Hereditary localized pruritus", "Posterior pigmented pruritic patch", and "subscapular pruritus") is a chronic sensory neuropathy. Notalgia paresthetica is a common localized itch, affecting mainly the area between the shoulder blades (especially the T2–T6 dermatomes) but occasionally with a more widespread distribution, involving the shoulders, back, and upper chest. : 402  The characteristic symptom is pruritus (itch or sensation that makes a person want to scratch) on the back, usually on the left hand side below the shoulder blade (mid to upper back). It is occasionally accompanied by pain, paresthesia (pins and needles), or hyperesthesia (unusual or pathologically increased sensitivity of the skin to sensory stimuli, such as pain, heat, cold, or touch), which results in a well circumscribed hyperpigmentation of a skin patch in the affected area. Causes
The correlation of notalgia paresthetica localization with corresponding degenerative changes in the spine suggests that spinal nerve impingement may be a contributing cause. According to Plete and Massey, "The posterior rami of spinal nerves arising in T2 through T6 are unique in that they pursue a right-angle course through the multifidus spinae muscle, and this particular circumstance may predispose them to harm from otherwise innocuous insults of a varied nature." Patients may have other conditions that predispose them to peripheral neuropathies (nerve damage).The causes of this condition have not yet been completely defined. Patients are usually older persons. Diagnosis
Treatment
Therapy for notalgia paresthetica is directed at controlling symptoms, as no cure exists for the condition.