Oropharyngeal Irritant Plants

Oropharyngeal Irritant Plants

Dumbcane

Other Common Names

Dumbplant; Mother-in-law’s tongue; Tuftroot.

Botanical Name

Dieffenbachia species.

Physical Appearance

This plant belonging to family Araceae can grow up to 6 feet, and has a fleshy, waxy stem with large, smooth leaves that are generally green on the periphery and mottled white in the center (Fig 10.1).

Uses

It is a popular ornamental houseplant. While most houseplants are non-toxic (Table 10.1), dumbcane is among the few exceptions.

Toxic Part

All parts, especially leaves.

Toxic Principle

Calcium oxalate crystals.

Mode of Action

■■  The leaves and stem contain high amounts of insolublecalcium oxalate in the form of needle-like crystals packaged in raphides and bundled into elongated idioblasts. The idio-blasts are cigar shaped structures with specialised nozzles at each end, capable of firing the needle-like raphides in the form of projectiles when force is applied (e.g. chewing). Thus when a leaf is bitten into, thousands of idioblasts fire the needle-like calcium oxalate crystals which penetrate mucous membranes and deposit proteolytic enzymes. The latter stimulate a cascade of events leading to release of bradykinin and histamine.

■■   Studies on Dieffenbachia picta in guinea pigs demonstrated the most toxic part of the plant was the stem juice, which, when dropped into the mouths of the animals, caused lip and tongue oedema, nasal secretions and progressive respiratory difficulties.

Clinical Features

·      Most cases of dumbcane poisoning involve oral exposure causing immediate and severe symptoms of pain and local swelling. Patients often describe the intense agony as akin to chewing powdered glass. There is severe swelling of the lips, mouth, and tongue, with salivation. There may be interference with swallowing and breathing. Oral paraes-thesia, with severe pain and numbness in the perioral area may occur.

·      Ocular exposure to expressed sap may cause immediate pain, lacrimation, photophobia, corneal abrasions, and deposition of calcium oxalate crystals on the corneal epithe-lium.

·      Systemic toxicity due to calcium oxalate is rare. Bloody emesis and diarrhoea may occur. Vomiting may be profuse. Following large ingestions, oxalic acid is formed in the stomach and subsequently absorbed into the systemic circulation. There it binds with calcium, and may cause hypocalcaemia. This could lead to weak, irregular pulse, bradycardia, hypotension, and cardiac dysrhythmias.

Treatment

1.   In patients with severe poisoning, examine the urine for calcium oxalate crystals. Also, monitor calcium and renal function (BUN, creatinine).

2.   Local treatment with cold milk or ice cream as a demulcent is sufficient in most cases. Cold water or sucking on crushed ice will also relieve oral pain. Remove all visible evidence of plant debris from the oropharynx.

3.   In severe cases, parenteral opioids, corticosteroids, IV fluids, and endotracheal intubation may be required. Tetany should be treated with intravenous calcium gluconate.

4.   Ocular exposure to sap resulting in chemical conjuncti-vitis and corneal abrasions must be treated with copious irrigation, systemic analgesics, and expert ophthalmologic consultation.

Philodendron

There are over 200 species of Philodendron. They are epiphytic herbs, primarily with climbing stems. They rarely stand erect. Identification is difficult because of the many different sizes and shapes of the leaves.

Other Common Names

Panda plant; Parlor ivy.

Botanical Name

Philodendron.

Physical Appearance

 Small plant with variously shaped, glossy, dark green leaves (Fig 10.2).

Uses

Popular houseplant.

Toxic Part

Leaves, stem.

Mode of Action

·              This plant contains calcium oxalate crystals, and causes GI irritation and local swelling. The raphides are contained in ampoule-like cells that, when ruptured by chewing or crushing, eject their contents into tissue. It appears that the rupturing of these cells, and the injection of the cell contents occurs at the same time. Crystallographic evidence indicatesthat there is some free oxalic acid in the cells.

·              The raphides may also be coated with various proteolytic enzymes which produce additional tissue damage.

Clinical Features

1.    Mild GI distress: Dysphagia, nausea, vomiting, oral pain, and perioral swelling may occur. Stomatitis, swelling of the tongue, and excessive salivation may be seen after ingestion.

2.   Hypocalcaemia and tetany are unlikely unless large amount has been ingested.

3.   Cutaneous exposure results in delayed contact dermatitis in sensitised individuals, due to the presence of resorcinol (an alkyl agent). Allergic contact dermatitis has been reported in a number of cases.

Usual Fatal Dose

Philodendrons may have as much as 0.7% oxalates. As little as 5 grams may be fatal. This would represent over 700 grams of leaves.

Treatment

·      General measures:

o     Dilution with milk or water may be of benefit by washing out the crystals and assisting in decontamina-tion of the oral pharynx.

o     Cold water or ice pack application may relieve local pain in the mouth.

·      Analgesics may be required if the pain is intense.

·      If large amounts have been ingested, the urine may be examined for oxalate crystals, but so far, crystals have not been reported after philodendron ingestion.

·      Corticosteroid dressings have been recommended for treat-ment of allergic dermatitis.