Go to start page
V1.6.13 T363
Disclaimer & Information
Show Mindmap
Poisonous animals
Cnidarians (Jellyfish, Corals and Anemones)
Venomous fish
Hymenopterans (Bees, Wasps and Ants)
Sea snakes
Terrestrial snakes
Miscellaneous animals

Diagnosis & Treatment — Hospital


Who requires antivenom?

Autopharmacological effects

Experimental and clinical observations suggest that the major systemic effects of envenoming are caused by endogenous catecholamines and acetylcholine, which are released in response to certain spider venoms. As these are transmitters in the sympathetic, parasympathetic and somatic nervous systems, the resulting clinical symptoms of envenoming are dealt with in the section "Neurological effects".

Local effects

S  Signs & Symptoms


  • Pain
  • redness
  • swelling
  • Local skin necorsis (Loxosceles; necrotic araneism)

Eyes (urticating hairs):

  • conjunctivitis
  • keratitis
  • iritis
  • chorioretinitis
D  Diagnostics
C  Comments

Local pain

Loxosceles sp. bites initially often go annoticed.

Latrodectus sp. bites are very painful with minimal (L. mactans) or moderate (L. hasselti) local signs.


Generalized pain

See comments below ('Neurological effects') and clinical entries of the individual spiders in the biomedical datebase.


Local skin necrosis (Loxosceles; necrotic araneism)

The majority of necroses caused by spider bites heal well without further measures if the wound is well cared for. The managment of severe necrotising processes following Loxosceles sp. bites (necrotic araneism) remains a problem. Standard therapy has not been developed.

Conservative treatment: RICE (rest, ice compression, eleveation) and antibiotics if needed (Sams et al 2001a,b).

According to several North American authors, they are best treated with analgesics and dapsone 25–100 mg, p.o., 12-hourly. Test for G-6-PDH deviciency.  However, the indications for dapsone treatment must be carefully weighed, as severe adverse reactions are possible (Wille and Morrow 1988, Kunkel 1988, Sams et al 2001). The contra-indications for dapsone must be kept in mind (Sams et al 2001a,b). Early surgical excision is  avoided (Futrell 1992, King and Rees 1983, 1986, Rees et al. 1985).

Numerous differential diagnoses for skin necrosis need to be considered, including infections, foreign bodies, focal vasculitis, self-administered injections, fat herniation with infarction, mechanical trauma, medications (heparin, coumarin) and pyoderma gangrenosum (Wasserman and Anderson 1983–84). It is particularly important to consider these differential diagnoses if no spider was seen and clearly identified as having caused the skin necrosis.

In summary, good evidence  for the efficacy of dapsone is lacking.

T  Treatment
  • Wound dressing and care,
  • possibly antibiotic treatment,
  • treatment of eye injuries.

Spiders that cause local pain, redness and swelling

In principle all spiders, local swelling can be minimal in neurotoxic araneism; see Biomedical database entries.

Spiders that cause severe skin necrosis

Spiders that cause damage to the eyes through contact with urticating hairs

Haemostatic effects

D  Diagnostics
  • Clinical,
  • laboratory parameters: Hb, Hct, clotting time, PT/aPTT, TT, fibrinogen, FSP, D-dimers, platelets.

Haemolytic effects

D  Diagnostics
  • Clinical,
  • laboratory parameters: Hb, Hct, LDH, haptoglobin.
C  Comments

Haemolysis has been observed following spider bites, but appears to be rare. However, it may occur with some delay (24–72 h to 2–3 days). It is therefore necessary to ensure that the patient is followed up for a corresponding period of time (Wasserman and Anderson 1983–84).

If haemolysis occurs: investigation of renal function and prevention or treatment of acute renal failure.

It is not possible to definitively conclude to what extent there is a haemostatic effect of spider venoms that is relevant to humans.

Spiders that cause haemolytic effects

Neurological effects

Neurotoxic araneism



  • vomiting,
  • profuse sweating,
  • hypersalivation,
  • increased bronchial secretion,
  • priapism,
  • bradycardia,
  • arterial hypotension;


  • tachycardia, arrhythmias,
  • arterial hypertension,
  • hyperglycaemia;


  • neuromuscular dysfunction of the skeletal musculature (muscle fasciculations and spasms, muscle pain, motor agitation).
D  Diagnostics
  • Clinical,
  • ECG,
  • chest X-ray,
  • blood gases,
  • blood sugar.
T  Treatment

Respiratory insufficiency/respiratory failure due to heavy bronchial secretion or pulmonary oedema: early endotracheal intubation, suctioning of bronchial secretions and artificial respiration. Caution is required in the treatment of pulmonary oedema with diuretics if there is concurrent hypovolaemia. Moreover, treatment with diuretics may not be successful anyway, as the pulmonary oedema may have a non-cardiogenic cause (increased capillary permeability). PEEP ventilation.

Hypovolaemia: caution is required in correcting hypovolaemia if there is concurrent pulmonary oedema.

Muscle pains and cramps:

  • Evdience for efficacy of symptomatic treatments suggested so far is missing.
  • Good evidence that antivenom is effective

Medications that are contraindicated or to be avoided: opiates, benzodiazepines.

C  Comments

Some species of spiders cause envenoming that is characterised by generalised autonomic and neuromuscular effects. Both parts of the autonomic nervous system and the somatic nervous system are stimulated. This results in cholinergic, adrenergic and somatic effects. There is a risk that severe cramping abdominal pain and board-like abdominal rigidity may be misdiagnosed as acute abdomen, leading to unnecessary laparotomies.

Pulmonary oedema has been observed following spider bites (aetiology: cardiogenic/non-cardiogenic?).


Antivenom is considered effective for the treatment of systemic effects (Sutherland 1992, Dieckman et al. 1989, Hartman and Sutherland 1984, Maretic 1983, Müller 1993; Warrell 2010).


Pain control:

Although calcium gluconate usually has been considered the first-line treatment of severe envenomations by black widow spiders, it was found ineffective for pain relief compared with a combination of i.v. opioids and benzodiazepines. The use of antivenom significantly shortened the duration of symptoms in severe envenomations (Clark. et al 1992).

Antivenom should be administered in most cases for pain relief alone, but the intramuscular route needs to be reconsidered with a controlled clinical trial (Isbister and Gray 2003).

Latrodectus spp.: Calcium gluconate (10 ml of a 10% solution, slowly iv) to relief pain of muscle spasms caused by  more rapidly and effectively than muscle relaxants (diazepam, methocarbamol): the evidence for efficacy is lacking (Warrell 2010).

Lampropelma nigerrimum: Oral diazepam and calcium gluconate injections without convincing effects on the spasms (Ahmed, Pinkham and Warrell 2009).

C  Comments

Antivenom is considered effective for the treatment of systemic effects (Sutherland 1992, Dieckman et al. 1989, Hartman and Sutherland 1984, Maretic 1983, Müller 1993; Warrell 2010).

How is the appropriate antivenom chosen?

D  Diagnostics
C  Comments

See also Isbister et al. 2003 Antivenom Treatment in Arachnidism.

How are antivenoms administered and complications caused by antivenoms treated?

T  Treatment

Monitoring of the patient
1. After administration of antivenom (assessment of success of antivenom or indication for continued antivenom treatment)

D  Diagnostics

Specific examinations are based on the signs and symptoms as well as laboratory parameters that were used to determine the indications for antivenom administration.

2. If there is no indication for antivenom treatment following the initial investigation

D  Diagnostics

At least hourly from 12 to 24 h after the sting: signs and symptoms listed in the section "Is it likely that a clinically relevant injection of venom has taken place?" in the Therapy phase: General practitioner / health post.

1. Wounds, in particular necrosis

D  Diagnostics
  • Inspection,
  • bacterial swabs.

C  Comments

see comments under 'local effects' above, in particular Loxosceles sp. (necrotic araneism).

2. If antivenom was administered: serum sickness

D  Diagnostics
T  Treatment